fix: Reset block style completely when leaving element to prevent bleeding styles

## Summary

Adds Xteink X3 hardware support to CrossPoint Reader. The X3 uses the
same SSD1677 e-ink controller as the X4 but with a different panel
(792x528 vs 800x480), different button layout, and an I2C fuel gauge
(BQ27220) instead of ADC-based battery reading.

All X3-specific behavior is gated by runtime device detection — X4
behavior is unchanged.

Depends on community-sdk X3 support: open-x4-epaper/community-sdk#19
(merged).

## Changes

### HAL Layer

**HalGPIO** (`lib/hal/HalGPIO.cpp/.h`)
- I2C-based device fingerprinting at boot: probes for BQ27220 fuel
gauge, DS3231 RTC, and QMI8658 IMU to distinguish X3 from X4
- Detection result cached in NVS for fast subsequent boots
- Exposes `deviceIsX3()` / `deviceIsX4()` helpers used throughout the
codebase
- X3 button mapping (7 GPIOs vs X4's layout)
- USB connection detection and wake classification for X3

**HalDisplay** (`lib/hal/HalDisplay.cpp/.h`)
- Calls `einkDisplay.setDisplayX3()` before init when X3 is detected
- Requests display resync after power button / flash wake events
- Runtime display dimension accessors (`getDisplayWidth()`,
`getDisplayHeight()`, `getBufferSize()`)
- Exposed as global `display` instance for use by image converters

**HalPowerManager** (`lib/hal/HalPowerManager.cpp/.h`)
- X3 battery reading via I2C fuel gauge (BQ27220 at 0x55, SOC register)
- X3 power button uses GPIO hold for deep sleep

### Display & Rendering

**GfxRenderer** (`lib/GfxRenderer/GfxRenderer.cpp/.h`)
- Buffer size and display dimensions are now runtime values (not
compile-time constants) to support both panel sizes
- X3 anti-aliasing tuning: only the darker grayscale level is applied to
avoid washed-out text on the X3 panel. X4 retains both levels via
`deviceIsX4()` gate

**Image Converters** (`lib/JpegToBmpConverter`, `lib/PngToBmpConverter`)
- Cover image prescale target uses runtime display dimensions from HAL
instead of hardcoded 800x480

### UI Themes

**BaseTheme / LyraTheme** (`src/components/themes/`)
- X3 button position mapping for the different physical layout
- Adjusted UI element positioning for 792x528 viewport

### Boot & Init

**main.cpp**
- X3 hardware detection logging
- Adjusted init sequence for X3 (no `HalSystem::begin()` dependency on
X3 path)

**HomeActivity**
- Uses runtime `renderer.getBufferSize()` instead of static
`GfxRenderer::getBufferSize()`

FYI I did not add support for the gyro page turner. That can be it's own
PR.

.github/skills/crosspoint-reader.md

@@ -0,0 +1 @@
+../../.skills/SKILL.md

.github/workflows/ci.yml

@@ -44,8 +44,14 @@ jobs:
         with:
           python-version: '3.14'
 
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+        with:
+          version: "latest"
+          enable-cache: false
+
       - name: Install PlatformIO Core
-        run: pip install --upgrade platformio
+        run: uv pip install --system -U https://github.com/pioarduino/platformio-core/archive/refs/tags/v6.1.19.zip
 
       - name: Run cppcheck
         run: pio check --fail-on-defect low --fail-on-defect medium --fail-on-defect high
@@ -61,8 +67,14 @@ jobs:
         with:
           python-version: '3.14'
 
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+        with:
+          version: "latest"
+          enable-cache: false
+
       - name: Install PlatformIO Core
-        run: pip install --upgrade platformio
+        run: uv pip install --system -U https://github.com/pioarduino/platformio-core/archive/refs/tags/v6.1.19.zip
 
       - name: Build CrossPoint
         run: |

.github/workflows/release.yml

@@ -12,19 +12,18 @@ jobs:
         with:
           submodules: recursive
 
-      - uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cache/pip
-            ~/.platformio/.cache
-          key: ${{ runner.os }}-pio
-
       - uses: actions/setup-python@v6
         with:
           python-version: '3.14'
 
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+        with:
+          version: "latest"
+          enable-cache: false
+
       - name: Install PlatformIO Core
-        run: pip install --upgrade platformio
+        run: uv pip install --system -U https://github.com/pioarduino/platformio-core/archive/refs/tags/v6.1.19.zip
 
       - name: Build CrossPoint
         run: pio run -e gh_release

.github/workflows/release_candidate.yml

@@ -12,19 +12,18 @@ jobs:
         with:
           submodules: recursive
 
-      - uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cache/pip
-            ~/.platformio/.cache
-          key: ${{ runner.os }}-pio
-
       - uses: actions/setup-python@v6
         with:
           python-version: '3.14'
 
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+        with:
+          version: "latest"
+          enable-cache: false
+
       - name: Install PlatformIO Core
-        run: pip install --upgrade platformio
+        run: uv pip install --system -U https://github.com/pioarduino/platformio-core/archive/refs/tags/v6.1.19.zip
 
       - name: Extract env
         run: |

.gitignore

@@ -3,6 +3,8 @@
 .DS_Store
 .vscode
 lib/EpdFont/fontsrc
+lib/I18n/I18nKeys.h
+lib/I18n/I18nStrings.h
 lib/I18n/I18nStrings.cpp
 *.generated.h
 .vs
@@ -10,3 +12,6 @@ build
 **/__pycache__/
 /compile_commands.json
 /.cache
+.history/
+/.venv
+*.local*

.skills/SKILL.md

@@ -0,0 +1,872 @@
+# CrossPoint Reader Development Guide
+
+Project: Open-source e-reader firmware for Xteink X4 (ESP32-C3)
+Mission: Provide a lightweight, high-performance reading experience focused on EPUB rendering on constrained hardware.
+
+## AI Agent Identity and Cognitive Rules
+* Role: Senior Embedded Systems Engineer (ESP-IDF/Arduino-ESP32 specialized).
+* Primary Constraint: 380KB RAM is the hard ceiling. Stability is non-negotiable.
+* Evidence-Based Reasoning: Before proposing a change, you MUST cite the specific file path and line numbers that justify the modification.
+* Anti-Hallucination: Do not assume the existence of libraries or ESP-IDF functions. If you are unsure of an API's availability for the ESP32-C3 RISC-V target, check the open-x4-sdk or official docs first.
+* No Unfounded Claims: Do not claim performance gains or memory savings without explaining the technical mechanism (e.g., DRAM vs IRAM usage).
+* Resource Justification: You must justify any new heap allocation (new, malloc, std::vector) or explain why a stack/static alternative was rejected.
+* Verification: After suggesting a fix, instruct the user on how to verify it (e.g., monitoring heap via Serial or checking a specific cache file).
+---
+
+## Development Environment Awareness
+
+**CRITICAL**: Detect the host platform at session start to choose appropriate tools and commands.
+
+### Platform Detection
+```bash
+# Detect platform (run once per session)
+uname -s
+# Returns: MINGW64_NT-* (Windows Git Bash), Linux, Darwin (macOS)
+```
+
+**Detection Required**: Run `uname -s` at session start to determine platform
+
+### Platform-Specific Behaviors
+- **Windows (Git Bash)**: Unix commands, `C:\` paths in Windows but `/` in bash, limited glob (use `find`+`xargs`)
+- **Linux/WSL**: Full bash, Unix paths, native glob support
+
+**Cross-Platform Code Formatting**:
+```bash
+find src -name "*.cpp" -o -name "*.h" | xargs clang-format -i
+```
+
+---
+
+## Platform and Hardware Constraints
+
+### Hardware Specs
+* MCU: ESP32-C3 (Single-core RISC-V @ 160MHz)
+* RAM: ~380KB usable (VERY LIMITED - primary project constraint)
+  * **NO PSRAM**: ESP32-C3 has no PSRAM capability (unlike ESP32-S3)
+  * **Single Buffer Mode**: Only ONE 48KB framebuffer (not double-buffered)
+* Flash: 16MB (Instruction storage and static data)
+* Display: 800x480 E-Ink (Slow refresh, monochrome, 1-2s full update)
+  * Framebuffer: 48,000 bytes (800 × 480 ÷ 8)
+* Storage: SD Card (Used for books and aggressive caching)
+
+### The Resource Protocol
+1. Stack Safety: Limit local function variables to < 256 bytes. The ESP32-C3 default stack is small; use std::unique_ptr or static pools for larger buffers.
+2. Heap Fragmentation: Avoid repeated new/delete in loops. Allocate buffers once during onEnter() and reuse them.
+3. Flash Persistence: Large constant data (UI strings, lookup tables) MUST be marked static const to stay in Flash (Instruction Bus), freeing DRAM.
+4. String Policy: Prohibit std::string and Arduino String in hot paths. Use std::string_view for read-only access and snprintf with fixed char[] buffers for construction.
+5. UI Strings: All user-facing text must use the `tr()` macro (e.g., `tr(STR_LOADING)`) for i18n support. Never hardcode UI strings directly. For the avoidance of doubt, logging messages (LOG_DBG/LOG_ERR) can be hardcoded, but user-facing text must use `tr()`.
+6. `constexpr` First: Compile-time constants and lookup tables must be `constexpr`, not just `static const`. This moves computation to compile time, enables dead-branch elimination, and guarantees flash placement. Use `static constexpr` for class-level constants.
+7. `std::vector` Pre-allocation: Always call `.reserve(N)` before any `push_back()` loop. Each growth event allocates a new block (2×), copies all elements, then frees the old one — three heap operations that fragment DRAM. When the final size is unknown, estimate conservatively.
+8. SPIFFS Write Throttling: Never write a settings file on every user interaction. Guard all writes with a value-change check (`if (newVal == _current) return;`). Progress saves during reading must be debounced — write on activity exit or every N page turns, not on every turn. SPIFFS sectors have a finite erase cycle limit.
+
+---
+
+## Project Architecture
+
+### Build System: PlatformIO
+
+**PlatformIO is BOTH a VS Code extension AND a CLI tool**:
+
+1. **VS Code Extension** (Recommended):
+   * Extension ID: `platformio.platformio-ide` (see `.vscode/extensions.json`)
+   * Provides: Toolbar buttons, IntelliSense, integrated build/upload/monitor
+   * Configuration: `.vscode/c_cpp_properties.json`, `.vscode/tasks.json`
+   * Usage: Click Build (✓), Upload (→), or Monitor (🔌) buttons
+
+2. **CLI Tool** (`pio` command):
+   * **Installation**: Python package (typically `pip install platformio`)
+   * **Windows Location**: `C:\Users\<user>\AppData\Local\Programs\Python\Python3xx\Scripts\pio.exe`
+   * **Verify**: `which pio` (Git Bash) or `where.exe pio` (cmd)
+   * **Usage**: `pio run`, `pio run -t upload`, etc.
+
+**Configuration Files**:
+* `platformio.ini`: Main build configuration (committed to git)
+* `platformio.local.ini`: Local overrides (gitignored, create if needed)
+* `partitions.csv`: ESP32 flash partition layout
+
+### Build Environment
+* **Standard**: C++20 (`-std=c++2a`). No Exceptions, No RTTI.
+* **Logging**: ALWAYS use `LOG_INF`, `LOG_DBG`, or `LOG_ERR` from `Logging.h`. Raw Serial output is deprecated.
+* **Environments** (in `platformio.ini`):
+  * `default`: Development (LOG_LEVEL=2, serial enabled)
+  * `gh_release`: Production (LOG_LEVEL=0)
+  * `gh_release_rc`: Release candidate (LOG_LEVEL=1)
+  * `slim`: Minimal build (no serial logging)
+
+### Critical Build Flags
+These flags in `platformio.ini` fundamentally affect firmware behavior:
+
+```cpp
+-DEINK_DISPLAY_SINGLE_BUFFER_MODE=1  // Single framebuffer (saves 48KB RAM!)
+-DARDUINO_USB_MODE=1                 // Enable USB CDC
+-DARDUINO_USB_CDC_ON_BOOT=1          // Serial available immediately at boot
+-DXML_CONTEXT_BYTES=1024             // XML parser memory limit (EPUB parsing)
+-DUSE_UTF8_LONG_NAMES=1              // SD card long filename support
+-DMINIZ_NO_ZLIB_COMPATIBLE_NAMES=1   // Avoid zlib name conflicts
+-DXML_GE=0                           // Disable XML general entities (security)
+```
+
+**SINGLE_BUFFER_MODE implications**:
+- Only ONE framebuffer exists (not double-buffered)
+- Grayscale rendering requires temporary buffer allocation (`renderer.storeBwBuffer()`)
+- Must call `renderer.restoreBwBuffer()` to free temporary buffers
+- See [lib/GfxRenderer/GfxRenderer.cpp:439-440](../lib/GfxRenderer/GfxRenderer.cpp) for malloc usage
+
+### Directory Structure
+* lib/: Internal libraries (Epub engine, GfxRenderer, UITheme, I18n)
+  * lib/hal/: Hardware Abstraction Layer (HalDisplay, HalGPIO, HalStorage)
+  * lib/I18n/: Internationalization (translations in `translations/*.yaml`, generated string tables)
+* src/activities/: UI logic using the Activity Lifecycle (onEnter, loop, onExit)
+* open-x4-sdk/: Low-level SDK (EInkDisplay, InputManager, BatteryMonitor, SDCardManager)
+* .crosspoint/: SD-based binary cache for EPUB metadata and pre-rendered layout sections
+
+### Hardware Abstraction Layer (HAL)
+
+**CRITICAL**: Always use HAL classes, NOT SDK classes directly.
+
+| HAL Class | Wraps SDK Class | Purpose | Singleton Macro |
+|-----------|----------------|---------|-----------------|
+| `HalDisplay` | `EInkDisplay` | E-ink display control | *(none)* |
+| `HalGPIO` | `InputManager` | Button input handling | *(none)* |
+| `HalStorage` | `SDCardManager` | SD card file I/O | `Storage` |
+
+**Location**: [lib/hal/](../lib/hal/)
+
+**Why HAL?**
+- Provides consistent error logging per module
+- Abstracts SDK implementation details
+- Centralizes resource management
+
+**Example - HalStorage**:
+```cpp
+#include <HalStorage.h>
+
+// Use Storage singleton (defined via macro)
+FsFile file;
+if (Storage.openFileForRead("MODULE", "/path/to/file.bin", file)) {
+  // Read from file
+  file.close();  // Explicit close required
+}
+```
+
+**Usage**: See example above. Uses `FsFile` (SdFat), NOT Arduino `File`.
+
+---
+
+## Coding Standards
+
+### Naming Conventions
+* Classes: PascalCase (e.g., EpubReaderActivity)
+* Methods/Variables: camelCase (e.g., renderPage())
+* Constants: UPPER_SNAKE_CASE (e.g., MAX_BUFFER_SIZE)
+* Private Members: memberVariable (no prefix)
+* File Names: Match Class names (e.g., EpubReaderActivity.cpp)
+
+### Header Guards
+* Use #pragma once for all header files.
+
+### Memory Safety and RAII
+* Smart Pointers: Prefer std::unique_ptr. Avoid std::shared_ptr (unnecessary atomic overhead for a single-core RISC-V).
+* RAII: Use destructors for cleanup, but call file.close() or vTaskDelete() explicitly for deterministic resource release.
+
+### ESP32-C3 Platform Pitfalls
+
+#### `std::string_view` and Null Termination
+`string_view` is *not* null-terminated. Passing `.data()` to any C-style API (`drawText`, `snprintf`, `strcmp`, SdFat file paths) is undefined behaviour when the view is a substring or a view of a non-null-terminated buffer.
+
+**Rule**: `string_view` is safe only when passing to C++ APIs that accept `string_view`. For any C API boundary, convert explicitly:
+```cpp
+// WRONG - undefined behaviour if view is a substring:
+renderer.drawText(font, x, y, myView.data(), true);
+
+// CORRECT - guaranteed null-terminated:
+renderer.drawText(font, x, y, std::string(myView).c_str(), true);
+
+// CORRECT - for short strings, use a stack buffer:
+char buf[64];
+snprintf(buf, sizeof(buf), "%.*s", (int)myView.size(), myView.data());
+```
+
+#### `IRAM_ATTR` and Flash Cache Safety
+All code runs from flash via the instruction cache. During SPI flash operations (OTA write, SPIFFS commit, NVS update) the cache is briefly suspended. Any code that can execute during this window — ISRs in particular — must reside in IRAM or it will crash silently.
+
+```cpp
+// ISR handler: must be in IRAM
+void IRAM_ATTR gpioISR() { ... }
+
+// Data accessed from IRAM_ATTR code: must be in DRAM, never a flash const
+static DRAM_ATTR uint32_t isrEventFlags = 0;
+```
+
+**Rules**:
+- All ISR handlers: `IRAM_ATTR`
+- Data read by `IRAM_ATTR` code: `DRAM_ATTR` (a flash-resident `static const` will fault)
+- Normal task code does **not** need `IRAM_ATTR`
+
+#### ISR vs Task Shared State
+`xSemaphoreTake()` (mutex) **cannot** be called from ISR context — it will crash. Use the correct primitive for each communication direction:
+
+| Direction | Correct primitive |
+|---|---|
+| ISR → task (data) | `xQueueSendFromISR()` + `portYIELD_FROM_ISR()` |
+| ISR → task (signal) | `xSemaphoreGiveFromISR()` + `portYIELD_FROM_ISR()` |
+| Task → task | `xSemaphoreTake()` / mutex |
+| Simple flag (single writer ISR) | `volatile bool` + `portENTER_CRITICAL_ISR()` |
+
+#### RISC-V Alignment
+ESP32-C3 faults on unaligned multi-byte loads. Never cast a `uint8_t*` buffer to a wider pointer type and dereference it directly. Use `memcpy` for any unaligned read:
+
+```cpp
+// WRONG — faults if buf is not 4-byte aligned:
+uint32_t val = *reinterpret_cast<const uint32_t*>(buf);
+
+// CORRECT:
+uint32_t val;
+memcpy(&val, buf, sizeof(val));
+```
+
+This applies to all cache deserialization code and any raw buffer-to-struct casting. `__attribute__((packed))` structs have the same hazard when accessed via member reference.
+
+#### Template and `std::function` Bloat
+Each template instantiation generates a separate binary copy. `std::function<void()>` adds ~2–4 KB per unique signature and heap-allocates its closure. Avoid both in library code and any path called from the render loop:
+
+```cpp
+// Avoid — heap-allocating, large binary footprint:
+std::function<void()> callback;
+
+// Prefer — zero overhead:
+void (*callback)() = nullptr;
+
+// For member function + context (common activity callback pattern):
+struct Callback { void* ctx; void (*fn)(void*); };
+```
+
+When a template is necessary, limit instantiations: use explicit template instantiation in a `.cpp` file to prevent the compiler from generating duplicates across translation units.
+
+---
+
+### Error Handling Philosophy
+
+**Source**: [src/main.cpp:132-143](../src/main.cpp), [lib/GfxRenderer/GfxRenderer.cpp:10](../lib/GfxRenderer/GfxRenderer.cpp)
+
+**Pattern Hierarchy**:
+1. **LOG_ERR + return false** (90%): `LOG_ERR("MOD", "Failed: %s", reason); return false;`
+2. **LOG_ERR + fallback**: `LOG_ERR("MOD", "Unavailable"); useDefault();`
+3. **assert(false)**: Only for fatal "impossible" states (framebuffer missing)
+4. **ESP.restart()**: Only for recovery (OTA complete)
+
+**Rules**: NO exceptions, NO abort(), ALWAYS log before error return
+
+### Acceptable malloc/free Patterns
+
+**Source**: [src/activities/home/HomeActivity.cpp:166](../src/activities/home/HomeActivity.cpp), [lib/GfxRenderer/GfxRenderer.cpp:439-440](../lib/GfxRenderer/GfxRenderer.cpp)
+
+Despite "prefer stack allocation," malloc is acceptable for:
+1. **Large temporary buffers** (> 256 bytes, won't fit on stack)
+2. **One-time allocations** during activity initialization
+3. **Bitmap rendering buffers** (variable size, used briefly)
+
+**Pattern**:
+```cpp
+// Allocate
+auto* buffer = static_cast<uint8_t*>(malloc(bufferSize));
+if (!buffer) {
+  LOG_ERR("MODULE", "malloc failed: %d bytes", bufferSize);
+  return false;  // Handle allocation failure
+}
+
+// Use buffer
+processData(buffer, bufferSize);
+
+// Free immediately after use
+free(buffer);
+buffer = nullptr;
+```
+
+**Rules**:
+- **ALWAYS check for nullptr** after malloc
+- **Free immediately** after use (don't hold across multiple operations)
+- **Set to nullptr** after free (avoid use-after-free)
+- **Document size**: Comment why stack allocation was rejected
+
+**Examples in codebase**:
+- Cover image buffers: [HomeActivity.cpp:166](../src/activities/home/HomeActivity.cpp)
+- Text chunk buffers: [TxtReaderActivity.cpp:259](../src/activities/reader/TxtReaderActivity.cpp)
+- Bitmap rendering: [GfxRenderer.cpp:439-440](../lib/GfxRenderer/GfxRenderer.cpp)
+- OTA update buffer: [OtaUpdater.cpp:40](../src/network/OtaUpdater.cpp)
+
+---
+
+## UI and Orientation Guidelines
+
+### Orientation-Aware Logic
+* No Hardcoding: Never assume 800 or 480. Use renderer.getScreenWidth() and renderer.getScreenHeight().
+* Viewable Area: Use renderer.getOrientedViewableTRBL() to stay within physical bezel margins.
+
+### Logical Button Mapping
+
+**Source**: [src/MappedInputManager.cpp:20-55](../src/MappedInputManager.cpp)
+
+Constraint: Physical button positions are fixed on hardware, but their logical functions change based on user settings and screen orientation.
+
+**Button Categories**:
+1. **Physical Fixed** (Up/Down side buttons):
+   - `Button::Up` → Always `HalGPIO::BTN_UP`
+   - `Button::Down` → Always `HalGPIO::BTN_DOWN`
+
+2. **User Remappable** (Front buttons):
+   - `Button::Back` → Maps to `SETTINGS.frontButtonBack` (hardware index)
+   - `Button::Confirm` → Maps to `SETTINGS.frontButtonConfirm`
+   - `Button::Left` → Maps to `SETTINGS.frontButtonLeft`
+   - `Button::Right` → Maps to `SETTINGS.frontButtonRight`
+
+3. **Reader-Specific** (Page navigation with optional swap):
+   - `Button::PageBack` → Uses side button (swappable via `SETTINGS.sideButtonLayout`)
+   - `Button::PageForward` → Uses side button (swappable)
+
+**Implementation**:
+- Activities use **logical buttons** (e.g., `Button::Confirm`)
+- `MappedInputManager` translates to **physical hardware buttons**
+- User can remap front buttons in settings
+- Orientation changes handled separately by renderer coordinate transforms
+
+**Rule**: Always use `MappedInputManager::Button::*` enums, never raw `HalGPIO::BTN_*` indices (except in ButtonRemapActivity).
+
+### UITheme (The GUI Macro)
+* Rule: All UI rendering must go through the GUI macro (UITheme). 
+* Do not hardcode fonts, colors, or positioning. This ensures orientation-aware layout consistency.
+
+---
+
+## Common Patterns
+
+### Singleton Access
+**Available Singletons**:
+```cpp
+#define SETTINGS CrossPointSettings::getInstance()  // User settings
+#define APP_STATE CrossPointState::getInstance()    // Runtime state
+#define GUI UITheme::getInstance()                   // Current theme
+#define Storage HalStorage::getInstance()            // SD card I/O
+#define I18N I18n::getInstance()                     // Internationalization
+```
+
+### Activity Lifecycle and Memory Management
+
+**Source**: [src/main.cpp:132-143](../src/main.cpp)
+
+**CRITICAL**: Activities are **heap-allocated** and **deleted on exit**.
+
+```cpp
+// main.cpp navigation pattern
+void exitActivity() {
+  if (currentActivity) {
+    currentActivity->onExit();
+    delete currentActivity;  // Activity deleted here!
+    currentActivity = nullptr;
+  }
+}
+
+void enterNewActivity(Activity* activity) {
+  currentActivity = activity;  // Heap-allocated activity
+  currentActivity->onEnter();
+}
+```
+
+**Memory Implications**:
+- Activity navigation = `delete` old activity + `new` create next activity
+- Any memory allocated in `onEnter()` MUST be freed in `onExit()`
+- FreeRTOS tasks MUST be deleted in `onExit()` before activity destruction
+- File handles MUST be closed in `onExit()`
+
+**Activity Pattern**:
+```cpp
+void onEnter()  { Activity::onEnter(); /* alloc: buffer, tasks */ render(); }
+void loop()     { mappedInput.update(); /* handle input */ }
+void onExit()   { /* free: vTaskDelete, free buffer, close files */ Activity::onExit(); }
+```
+
+**Critical**: Free resources in reverse order. Delete tasks BEFORE activity destruction.
+
+### FreeRTOS Task Guidelines
+
+**Source**: [src/activities/util/KeyboardEntryActivity.cpp:45-50](../src/activities/util/KeyboardEntryActivity.cpp)
+
+**Pattern**: See Activity Lifecycle above. `xTaskCreate(&taskTrampoline, "Name", stackSize, this, 1, &handle)`
+
+**Stack Sizing** (in BYTES, not words):
+- **2048**: Simple rendering (most activities)
+- **4096**: Network, EPUB parsing
+- Monitor: `uxTaskGetStackHighWaterMark()` if crashes
+
+**Rules**: Always `vTaskDelete()` in `onExit()` before destruction. Use mutex if shared state.
+
+### Global Font Loading
+
+**Source**: [src/main.cpp:40-115](../src/main.cpp)
+
+**All fonts are loaded as global static objects** at firmware startup:
+- Bookerly: 12, 14, 16, 18pt (4 styles each: regular, bold, italic, bold-italic)
+- Noto Sans: 12, 14, 16, 18pt (4 styles each)
+- OpenDyslexic: 8, 10, 12, 14pt (4 styles each)
+- Ubuntu UI fonts: 10, 12pt (2 styles)
+
+**Total**: ~80+ global `EpdFont` and `EpdFontFamily` objects
+
+**Compilation Flag**:
+```cpp
+#ifndef OMIT_FONTS
+  // Most fonts loaded here
+#endif
+```
+
+**Implications**:
+- Fonts stored in **Flash** (marked as `static const` in `lib/EpdFont/builtinFonts/`)
+- Font rendering data cached in **DRAM** when first used
+- `OMIT_FONTS` can reduce binary size for minimal builds
+- Font IDs defined in [src/fontIds.h](../src/fontIds.h)
+
+**Usage**:
+```cpp
+#include "fontIds.h"
+
+renderer.insertFont(FONT_UI_MEDIUM, ui12FontFamily);
+renderer.drawText(FONT_UI_MEDIUM, x, y, "Hello", true);
+```
+
+---
+
+## Testing and Debugging
+
+### Build Commands
+
+**Via CLI**:
+```bash
+# Build firmware (default environment)
+pio run
+
+# Build and upload to device
+pio run -t upload
+
+# Build specific environment
+pio run -e gh_release
+
+# Clean build artifacts
+pio run -t clean
+
+# Upload filesystem data (if using SPIFFS/LittleFS)
+pio run -t uploadfs
+```
+
+**Via VS Code**:
+* Use PlatformIO toolbar: Build (✓), Upload (→), Clean (🗑️)
+* Or Command Palette: `PlatformIO: Build`, `PlatformIO: Upload`, etc.
+
+### Monitoring and Debugging
+
+```bash
+# Enhanced monitor with color/logging (recommended)
+python3 scripts/debugging_monitor.py
+
+# Standard PlatformIO monitor
+pio device monitor
+
+# Combined upload + monitor
+pio run -t upload && pio device monitor
+```
+
+**Via VS Code**: Click Monitor (🔌) button in PlatformIO toolbar
+
+### Code Quality
+
+```bash
+# Static analysis (cppcheck)
+pio check
+
+# Format code (clang-format) - Windows Git Bash
+find src -name "*.cpp" -o -name "*.h" | xargs clang-format -i
+
+# Format code (clang-format) - Linux
+clang-format -i src/**/*.cpp src/**/*.h
+```
+
+### Debugging Crashes
+
+**Common Crash Causes**:
+
+1. **Out of Memory** (Most common):
+   ```cpp
+   LOG_DBG("MEM", "Free heap: %d bytes", ESP.getFreeHeap());
+   ```
+   - Monitor heap usage throughout activity lifecycle
+   - Check if large allocations (>10KB) occur before crash
+   - Verify buffers are freed in `onExit()`
+
+2. **Stack Overflow**:
+   ```cpp
+   LOG_DBG("TASK", "Stack high water: %d", uxTaskGetStackHighWaterMark(taskHandle));
+   ```
+   - Occurs during deep recursion or large local variables
+   - Increase task stack size in `xTaskCreate()` (2048 → 4096)
+   - Move large buffers to heap with malloc
+
+3. **Use-After-Free**:
+   - Activity deleted but task still running
+   - Always `vTaskDelete()` in `onExit()` BEFORE activity destruction
+   - Set pointers to `nullptr` after `free()`
+
+4. **Corrupt Cache Files**:
+   - Delete `.crosspoint/` directory on SD card
+   - Forces clean re-parse of all EPUBs
+   - Check file format versions in [docs/file-formats.md](../docs/file-formats.md)
+
+5. **Watchdog Timeout**:
+   - Loop/task blocked for >5 seconds
+   - Add `vTaskDelay(1)` in tight loops
+   - Check for blocking I/O operations
+
+**Verification Steps**:
+1. Check serial output for stack traces
+2. Monitor heap with `ESP.getFreeHeap()` before/after operations
+3. Verify task deletion with task list (`vTaskList()`)
+4. Test with `LOG_LEVEL=2` (debug logging enabled)
+
+---
+
+## Git Workflow and Repository Awareness
+
+### Repository Detection Protocol
+
+**CRITICAL**: ALWAYS verify repository context before git operations. This could be:
+- A **fork** with `origin` pointing to personal repo, `upstream` to main repo
+- A **direct clone** with `origin` pointing to main repo
+- Multiple collaborator remotes
+
+**Verification Commands** (run at session start):
+```bash
+# Check current branch
+git branch --show-current
+
+# Check all remotes
+git remote -v
+
+# Identify main branch name (could be 'main' or 'master')
+git symbolic-ref refs/remotes/origin/HEAD 2>/dev/null | sed 's@^refs/remotes/origin/@@'
+
+# Check working tree status
+git status --short
+```
+
+**Example Output** (forked repository):
+```text
+origin      https://github.com/<your-username>/crosspoint-reader.git (fetch/push)
+upstream    https://github.com/crosspoint-reader/crosspoint-reader.git (fetch/push)
+```
+
+### Git Operation Rules
+
+1. **Never assume branch names**:
+   ```bash
+   # Bad: git push origin main
+   # Good: git push origin $(git branch --show-current)
+   ```
+
+2. **Never assume remote names or write permissions**:
+   - **Forked repos**: Push to `origin` (your fork), submit PR to `upstream`
+   - **Direct contributors**: May push feature branches to `upstream`
+   - **Always ask**: "Should I push to origin or create a PR?"
+
+3. **Check for upstream changes before starting work**:
+   ```bash
+   # Sync fork with upstream (if applicable)
+   git fetch upstream
+   git merge upstream/main  # or upstream/master
+   ```
+
+4. **Use explicit remote and branch names**:
+   ```bash
+   # Check remotes first
+   git remote -v
+
+   # Use explicit syntax
+   git push <remote> <branch>
+   ```
+
+### Branch Naming Convention
+
+**For feature/fix branches**:
+```text
+feature/<short-description>       # New features
+fix/<issue-number>-<description>  # Bug fixes
+refactor/<component-name>         # Code refactoring
+docs/<topic>                      # Documentation updates
+```
+
+**Examples**:
+- `feature/sd-download-progress`
+- `fix/123-orientation-crash`
+- `refactor/hal-storage`
+
+### Commit Message Format
+
+**Pattern**:
+```text
+<type>: <short summary (50 chars max)>
+
+<optional detailed description>
+
+```
+
+**Types**: `feat`, `fix`, `refactor`, `docs`, `test`, `chore`, `perf`
+
+**Example**:
+```text
+feat: add real-time SD download progress bar
+
+Implements progress tracking for book downloads using
+UITheme progress bar component with heap-safe updates.
+
+Tested in all 4 orientations with 5MB+ files.
+```
+
+### When to Commit
+
+**DO commit when**:
+- User explicitly requests: "commit these changes"
+- Feature is complete and tested on device
+- Bug fix is verified working
+- Refactoring preserves all functionality
+- All tests pass (`pio run` succeeds)
+
+**DO NOT commit when**:
+- Changes are untested on actual hardware
+- Build fails or has warnings
+- Experimenting or debugging in progress
+- User hasn't explicitly requested commit
+- Files excluded by `.gitignore` would be included — always run `git status` and cross-check against `.gitignore` before staging (e.g., `*.generated.h`, `.pio/`, `compile_commands.json`, `platformio.local.ini`)
+
+**Rule**: **If uncertain, ASK before committing.**
+
+---
+
+## Generated Files and Build Artifacts
+
+### Files Generated by Build Scripts
+
+**NEVER manually edit these files** - they are regenerated automatically:
+
+1. **HTML Headers** (generated by `scripts/build_html.py`):
+   - `src/network/html/*.generated.h`
+   - **Source**: HTML templates in `data/html/` directory
+   - **Triggered**: During PlatformIO `pre:` build step
+   - **To modify**: Edit source HTML in `data/html/`, not generated headers
+
+2. **I18n Headers** (generated by `scripts/gen_i18n.py`):
+   - `lib/I18n/I18nKeys.h`, `lib/I18n/I18nStrings.h`, `lib/I18n/I18nStrings.cpp`
+   - **Source**: YAML translation files in `lib/I18n/translations/` (one per language)
+   - **To modify**: Edit source YAML files, then run `python scripts/gen_i18n.py lib/I18n/translations lib/I18n/`
+   - **Commit**: Source YAML files only. All three generated files (`I18nKeys.h`, `I18nStrings.h`, `I18nStrings.cpp`) are in `.gitignore` and regenerated at build time.
+
+3. **Build Artifacts** (in `.gitignore`):
+   - `.pio/` - PlatformIO build output
+   - `build/` - Compiled binaries
+   - `*.generated.h` - Any auto-generated headers
+   - `compile_commands.json` - LSP/IDE metadata
+
+### Modifying Generated Content Workflow
+
+**To change HTML pages**:
+1. Edit source: `data/html/<pagename>.html`
+2. Build: `pio run` (auto-triggers `scripts/build_html.py`)
+3. Generated headers update: `src/network/html/<pagename>Html.generated.h`
+4. **Commit ONLY** source HTML, NOT generated `.generated.h` files
+
+**To add/modify translations (i18n)**:
+1. Edit or add YAML file: `lib/I18n/translations/<language>.yaml`
+   - Each file must contain: `_language_name`, `_language_code`, `_order`, and `STR_*` keys
+   - English (`english.yaml`) is the reference; missing keys in other languages fall back to English
+2. Run generator: `python scripts/gen_i18n.py lib/I18n/translations lib/I18n/`
+3. Generated files update: `I18nKeys.h`, `I18nStrings.h`, `I18nStrings.cpp`
+4. **Commit** source YAML files only. All three generated files are in `.gitignore` and regenerated at build time.
+
+**To use translated strings in code**:
+```cpp
+#include <I18n.h>
+// Use tr() macro with StrId enum (defined in generated I18nKeys.h)
+renderer.drawText(FONT_UI, x, y, tr(STR_LOADING), true);
+```
+
+**To add custom fonts**:
+1. Place source fonts in `lib/EpdFont/fontsrc/` (gitignored)
+2. Run conversion script (see `lib/EpdFont/README`)
+3. Update global font objects in `src/main.cpp:40-115`
+4. Add font ID constant to `src/fontIds.h`
+
+---
+
+## Local Development Configuration
+
+### platformio.local.ini (Personal Overrides)
+
+**Purpose**: Personal development settings that should NEVER be committed.
+
+**Use Cases**:
+- Serial port configuration (varies by machine)
+- Debug flags for specific testing
+- Local build optimizations
+- Developer-specific paths
+
+**Example** `platformio.local.ini`:
+```ini
+# platformio.local.ini (gitignored)
+[env:default]
+upload_port = COM7              # Windows: COMx, Linux: /dev/ttyUSBx
+monitor_port = COM7
+
+build_flags =
+  ${base.build_flags}
+  -DMY_DEBUG_FLAG=1             # Personal debug flags
+  -DTEST_FEATURE_ENABLED=1
+```
+
+**Configuration Hierarchy**:
+1. `platformio.ini` - **Committed**, shared project settings
+2. `platformio.local.ini` - **Gitignored**, personal overrides
+3. Local file extends/overrides base config
+
+**Rules**:
+- **NEVER commit** `platformio.local.ini`
+- **NEVER put** personal info (serial ports, credentials) in main `platformio.ini`
+- Use `${base.build_flags}` to extend (not replace) base flags
+
+---
+
+## Testing and Verification Workflow
+
+### Testing Checklist
+
+**AI agent scope** (what you CAN verify):
+1. ✅ **Build**: `pio run -t clean && pio run` (0 errors/warnings)
+2. ✅ **Quality**: `pio check` + `find src -name "*.cpp" -o -name "*.h" | xargs clang-format -i`
+3. ✅ **Format**: Commit messages (`feat:`/`fix:`), no `.gitignore`-excluded files staged (e.g., `*.generated.h`, `.pio/`, `platformio.local.ini`)
+4. ✅ **CI**: Fix GitHub Actions failures before review
+5. ✅ **Code review**: Ensure orientation-aware logic is correct in all 4 modes by inspecting switch/case coverage
+
+**Human tester scope** (flag these for the user):
+6. 🔲 **Device**: Test on hardware
+7. 🔲 **Orientations**: Verify all 4 modes (Portrait/Inverted/Landscape CW/CCW)
+8. 🔲 **Heap**: `ESP.getFreeHeap()` > 50KB, no leaks
+9. 🔲 **Cache**: If EPUB modified, delete `.crosspoint/` and verify re-parse
+
+### CI/CD Pipeline Awareness
+
+**GitHub Actions** run automatically on pull requests:
+
+| Workflow | File | Purpose |
+|----------|------|---------|
+| Build Check | `.github/workflows/ci.yml` | Verifies code compiles |
+| Format Check | `.github/workflows/pr-formatting-check.yml` | Validates clang-format |
+| Release Build | `.github/workflows/release.yml` | Production releases |
+| RC Build | `.github/workflows/release_candidate.yml` | Release candidates |
+
+**Rules**:
+- **Fix CI failures BEFORE** requesting review
+- CI runs on: Push to PR, PR updates
+- Format check fails → Run clang-format locally
+- Build check fails → Fix compile errors
+
+---
+
+## Serial Monitoring and Live Debugging
+
+### Serial Monitor Options
+
+1. **Enhanced**: `python3 scripts/debugging_monitor.py` (color-coded, recommended)
+2. **Standard**: `pio device monitor` (basic, no colors)
+3. **VS Code**: Monitor (🔌) button (IDE-integrated)
+
+### Live Debugging Patterns
+
+**Heap**: `LOG_DBG("MEM", "Free: %d", ESP.getFreeHeap());` (every 5s in loop)
+**Stack**: `uxTaskGetStackHighWaterMark(nullptr)` (< 512 bytes → increase stack)
+**Flush**: `logSerial.flush();` (force output before crash)
+
+**Port Detection**: Windows: `mode` | Linux: `ls /dev/ttyUSB* /dev/ttyACM*` or `dmesg | grep tty`
+
+---
+
+## Cache Management and Invalidation
+
+### Cache Structure on SD Card
+
+**Location**: `.crosspoint/` directory on SD card root
+
+**Structure**: `.crosspoint/epub_<hash>/{book.bin, progress.bin, cover.bmp, sections/*.bin}`
+
+**Hash**: `std::hash<std::string>{}(filepath)` → Moving/renaming file = new hash = lost progress
+
+### Cache Invalidation Rules
+
+**Cache is automatically invalidated when**:
+1. **File format version changes** (see `docs/file-formats.md`)
+   - `book.bin` version number incremented
+   - `section.bin` version number incremented
+2. **Render settings change**:
+   - Font family or size (`SETTINGS.fontFamily`, `SETTINGS.fontSize`)
+   - Line spacing (`SETTINGS.lineSpacing`)
+   - Paragraph spacing (`SETTINGS.extraParagraphSpacing`)
+   - Screen margins (`SETTINGS.screenMargin`)
+3. **Viewport dimensions change**:
+   - Screen orientation change
+   - Display resolution change
+4. **Book file modified**:
+   - Moved, renamed, or content changed (new hash)
+
+**Manual Cache Clear** (safe operations):
+```bash
+# Delete ALL caches (forces full regeneration)
+rm -rf /path/to/sd/.crosspoint/
+
+# Delete specific book cache
+rm -rf /path/to/sd/.crosspoint/epub_<hash>/
+
+# Keep progress, delete only rendered sections
+rm -rf /path/to/sd/.crosspoint/epub_<hash>/sections/
+```
+
+**When to Clear Cache**:
+- EPUB parsing errors after code changes to `lib/Epub/`
+- Corrupt rendering (missing text, wrong layout)
+- Testing cache generation logic
+- After modifying:
+  - `lib/Epub/Epub/Section.cpp`
+  - `lib/Epub/Epub/BookMetadataCache.cpp`
+  - Render settings in `CrossPointSettings`
+
+### Cache File Format Versioning
+
+**Source**: `lib/Epub/Epub/Section.cpp`, `lib/Epub/Epub/BookMetadataCache.cpp`
+
+**Current Versions** (as of docs/file-formats.md):
+- `book.bin`: **Version 5** (metadata structure)
+- `section.bin`: **Version 12** (layout structure)
+
+**Version Increment Rules**:
+1. **ALWAYS increment version** BEFORE changing binary structure
+2. Version mismatch → Cache auto-invalidated and regenerated
+3. Document format changes in `docs/file-formats.md`
+
+**Example** (incrementing section format version):
+```cpp
+// lib/Epub/Epub/Section.cpp
+static constexpr uint8_t SECTION_FILE_VERSION = 13;  // Was 12, now 13
+
+// Add new field to structure
+struct PageLine {
+  // ... existing fields ...
+  uint16_t newField;  // New field added
+};
+```
+
+---
+
+Philosophy: We are building a dedicated e-reader, not a Swiss Army knife. If a feature adds RAM pressure without significantly improving the reading experience, it is Out of Scope.

CLAUDE.md

@@ -0,0 +1 @@
+.skills/SKILL.md

README.md

@@ -26,7 +26,7 @@ This project is **not affiliated with Xteink**; it's built as a community projec
 ## Features & Usage
 
 - [x] EPUB parsing and rendering (EPUB 2 and EPUB 3)
-- [ ] Image support within EPUB
+- [x] Image support within EPUB
 - [x] Saved reading position
 - [x] File explorer with file picker
   - [x] Basic EPUB picker from root directory
@@ -36,6 +36,7 @@ This project is **not affiliated with Xteink**; it's built as a community projec
   - [x] Cover sleep screen
 - [x] Wifi book upload
 - [x] Wifi OTA updates
+- [x] KOReader Sync integration for cross-device reading progress
 - [x] Configurable font, layout, and display options
   - [ ] User provided fonts
   - [ ] Full UTF support
@@ -43,7 +44,8 @@ This project is **not affiliated with Xteink**; it's built as a community projec
 
 Multi-language support: Read EPUBs in various languages, including English, Spanish, French, German, Italian, Portuguese, Russian, Ukrainian, Polish, Swedish, Norwegian, [and more](./USER_GUIDE.md#supported-languages).
 
-See [the user guide](./USER_GUIDE.md) for instructions on operating CrossPoint. 
+See [the user guide](./USER_GUIDE.md) for instructions on operating CrossPoint, including the
+[KOReader Sync quick setup](./USER_GUIDE.md#365-koreader-sync-quick-setup).
 
 For more details about the scope of the project, see the [SCOPE.md](SCOPE.md) document.
 
@@ -154,6 +156,8 @@ For more details on the internal file structures, see the [file formats document
 
 Contributions are very welcome!
 
+If you are new to the codebase, start with the [contributing docs](./docs/contributing/README.md).
+
 If you're looking for a way to help out, take a look at the [ideas discussion board](https://github.com/crosspoint-reader/crosspoint-reader/discussions/categories/ideas).
 If there's something there you'd like to work on, leave a comment so that we can avoid duplicated effort.
 

SCOPE.md

@@ -39,6 +39,14 @@ usability over "swiss-army-knife" functionality.
 * **Complex Annotation:** No typed out notes. These features are better suited for devices with better input
   capabilities and more powerful chips.
 
+### In-scope — Technically Unsupported
+
+*These features align with CrossPoint's goals but are impractical on the current hardware or produce poor UX.*
+
+* **Clock Display:** The ESP32-C3's RTC drifts significantly during deep sleep; making the clock untrustworthy after any sleep cycle. NTP sync could help, but CrossPoint doesn't connect to the internet on every boot.
+
+* **PDF Rendering:** PDFs are fixed-layout documents, so rendering them requires displaying pages as images rather than reflowable text — resulting in constant panning and zooming that makes for a poor reading experience on e-ink.
+
 ## 3. Idea Evaluation
 
 While I appreciate the desire to add new and exciting features to CrossPoint Reader, CrossPoint Reader is designed to be

USER_GUIDE.md

@@ -10,12 +10,18 @@ Welcome to the **CrossPoint** firmware. This guide outlines the hardware control
     - [First Launch](#first-launch)
   - [3. Screens](#3-screens)
     - [3.1 Home Screen](#31-home-screen)
-    - [3.2 Book Selection](#32-book-selection)
-    - [3.3 Reading Mode](#33-reading-mode)
-    - [3.4 File Upload Screen](#34-file-upload-screen)
-    - [3.4.1 Calibre Wireless Transfers](#341-calibre-wireless-transfers)
-    - [3.5 Settings](#35-settings)
-    - [3.6 Sleep Screen](#36-sleep-screen)
+    - [3.2 Reading Mode](#32-reading-mode)
+    - [3.3 Browse Files Screen](#33-browse-files-screen)
+    - [3.4 Recent Books Screen](#34-recent-books-screen)
+    - [3.5 File Transfer Screen](#35-file-transfer-screen)
+      - [3.5.1 Calibre Wireless Transfers](#351-calibre-wireless-transfers)
+    - [3.6 Settings](#36-settings)
+      - [3.6.1 Display](#361-display)
+      - [3.6.2 Reader](#362-reader)
+      - [3.6.3 Controls](#363-controls)
+      - [3.6.4 System](#364-system)
+      - [3.6.5 KOReader Sync Quick Setup](#365-koreader-sync-quick-setup)
+    - [3.7 Sleep Screen](#37-sleep-screen)
   - [4. Reading Mode](#4-reading-mode)
     - [Page Turning](#page-turning)
     - [Chapter Navigation](#chapter-navigation)
@@ -28,7 +34,7 @@ Welcome to the **CrossPoint** firmware. This guide outlines the hardware control
 
 ## 1. Hardware Overview
 
-The device utilises the standard buttons on the Xtink X4 (in the same layout as the manufacturer firmware, by default):
+The device utilises the standard buttons on the Xteink X4 (in the same layout as the manufacturer firmware, by default):
 
 ### Button Layout
 | Location        | Buttons                                              |
@@ -36,7 +42,12 @@ The device utilises the standard buttons on the Xtink X4 (in the same layout as
 | **Bottom Edge** | **Back**, **Confirm**, **Left**, **Right**           |
 | **Right Side**  | **Power**, **Volume Up**, **Volume Down**, **Reset** |
 
-Button layout can be customized in **[Settings](#35-settings)**.
+Button layout can be customized in the **[Controls Settings](#363-controls)**.
+
+### Taking a Screenshot
+When the Power Button and Volume Down button are pressed at the same time, it will take a screenshot and save it in the folder `screenshots/`.
+
+Alternatively, while reading a book, press the **Confirm** button to open the reader menu and select **Take screenshot**.
 
 ---
 
@@ -45,9 +56,9 @@ Button layout can be customized in **[Settings](#35-settings)**.
 ### Power On / Off
 
 To turn the device on or off, **press and hold the Power button for approximately half a second**.
-In **[Settings](#35-settings)** you can configure the power button to turn the device off with a short press instead of a long one.
+In the **[Controls Settings](#363-controls)** you can configure the power button to turn the device off with a short press instead of a long one.
 
-To reboot the device (for example if it's frozen, or after a firmware update), press and release the Reset button, and then quickly press and hold the Power button for a few seconds.
+To reboot the device (for example after a firmware update or if it's frozen), press and release the Reset button, and then quickly press and hold the Power button for a few seconds.
 
 ### First Launch
 
@@ -62,29 +73,34 @@ Upon turning the device on for the first time, you will be placed on the **[Home
 
 ### 3.1 Home Screen
 
-The Home Screen is the main entry point to the firmware. From here you can navigate to **[Reading Mode](#4-reading-mode)** with the most recently read book, **[Book Selection](#32-book-selection)**, **[Settings](#35-settings)**, or the **[File Upload](#34-file-upload-screen)** screen.
+The Home screen is the main entry point to the firmware. From here you can navigate to **[Reading Mode](#4-reading-mode)** with the most recently read book, the **[Browse Files](#33-browse-files-screen)** screen, the **[Recent Books](#34-recent-books-screen)** screen, the **[File Transfer](#35-file-transfer-screen)** screen, or **[Settings](#36-settings)**.
 
-### 3.2 Book Selection
-
-The Book Selection acts as a folder and file browser.
-
-* **Navigate List:** Use **Left** (or **Volume Up**), or **Right** (or **Volume Down**) to move the selection cursor up and down through folders and books. You can also long-press these buttons to scroll a full page up or down.
-* **Open Selection:** Press **Confirm** to open a folder or read a selected book.
-
-### 3.3 Reading Mode
+### 3.2 Reading Mode
 
 See [Reading Mode](#4-reading-mode) below for more information.
 
-### 3.4 File Upload Screen
+### 3.3 Browse Files Screen
 
-The File Upload screen allows you to upload new e-books to the device. When you enter the screen, you'll be prompted with a WiFi selection dialog and then your X4 will start hosting a web server.
+The Browse Files screen acts as a file and folder browser.
+
+* **Navigate List:** Use **Left** (or **Volume Up**), or **Right** (or **Volume Down**) to move the selection cursor up and down through folders and books. You can also long-press these buttons to scroll a full page up or down.
+* **Open Selection:** Press **Confirm** to open a folder or read a selected book. 
+* **Delete Files:** Hold and release **Confirm** to delete the selected file. You will be given an option to either confirm or cancel deletion. Folder deletion is not supported.
+
+### 3.4 Recent Books Screen
+
+The Recent Books screen lists the most recently opened books in a chronological view, displaying title and author.
+
+### 3.5 File Transfer Screen
+
+The File Transfer screen allows you to upload new e-books to the device. When you enter the screen, you'll be prompted with a WiFi selection dialog and then your X4 will start hosting a web server.
 
 See the [webserver docs](./docs/webserver.md) for more information on how to connect to the web server and upload files.
 
 > [!TIP]
 > Advanced users can also manage files programmatically or via the command line using `curl`. See the [webserver docs](./docs/webserver.md) for details.
 
-### 3.4.1 Calibre Wireless Transfers
+### 3.5.1 Calibre Wireless Transfers
 
 CrossPoint supports sending books from Calibre using the CrossPoint Reader device plugin.
 
@@ -96,23 +112,26 @@ CrossPoint supports sending books from Calibre using the CrossPoint Reader devic
 3. Make sure your computer is on the same WiFi network.
 4. In Calibre, click "Send to device" to transfer books.
 
-### 3.5 Settings
+### 3.6 Settings
 
 The Settings screen allows you to configure the device's behavior. There are a few settings you can adjust:
+
+#### 3.6.1 Display
+
 - **Sleep Screen**: Which sleep screen to display when the device sleeps:
   - "Dark" (default) - The default dark Crosspoint logo sleep screen
   - "Light" - The same default sleep screen, on a white background
-  - "Custom" - Custom images from the SD card; see [Sleep Screen](#36-sleep-screen) below for more information
+  - "Custom" - Custom images from the SD card; see [Sleep Screen](#37-sleep-screen) below for more information
   - "Cover" - The book cover image (Note: this is experimental and may not work as expected)
   - "None" - A blank screen
-  - "Cover + Custom" - The book cover image, fallbacks to "Custom" behavior
+  - "Cover + Custom" - The book cover image, falls back to "Custom" behavior
 - **Sleep Screen Cover Mode**: How to display the book cover when "Cover" sleep screen is selected:
   - "Fit" (default) - Scale the image down to fit centered on the screen, padding with white borders as necessary
-  - "Crop" - Scale the image down and crop as necessary to try to to fill the screen (Note: this is experimental and may not work as expected)
-- **Sleep Screen Cover Filter**: What filter will be applied to the book cover when "Cover" sleep screen is selected 
+  - "Crop" - Scale the image down and crop as necessary to try to fill the screen (Note: this is experimental and may not work as expected)
+- **Sleep Screen Cover Filter**: What filter will be applied to the book cover when "Cover" sleep screen is selected:
   - "None" (default) - The cover image will be converted to a grayscale image and displayed as it is
   - "Contrast" - The image will be displayed as a black & white image without grayscale conversion
-  - "Inverted" - The image will be inverted as in white&black and will be displayed without grayscale conversion
+  - "Inverted" - The image will be inverted as in white & black and will be displayed without grayscale conversion
 - **Status Bar**: Configure the status bar displayed while reading:
   - "None" - No status bar
   - "No Progress" - Show status bar without reading progress
@@ -120,56 +139,199 @@ The Settings screen allows you to configure the device's behavior. There are a f
   - "Full w/ Book Bar" - Show status bar with book progress (as bar)
   - "Book Bar Only" - Show book progress (as bar)
   - "Full w/ Chapter Bar" - Show status bar with chapter progress (as bar)
-- **Hide Battery %**: Configure where to suppress the battery pecentage display in the status bar; the battery icon will still be shown:
-  - "Never" - Always show battery percentage (default)
+- **Hide Battery %**: Configure where to suppress the battery percentage display in the status bar; the battery icon will still be shown:
+  - "Never" (default) - Always show battery percentage
   - "In Reader" - Show battery percentage everywhere except in reading mode
   - "Always" - Always hide battery percentage
-- **Extra Paragraph Spacing**: If enabled, vertical space will be added between paragraphs in the book. If disabled, paragraphs will not have vertical space between them, but will have first-line indentation.
-- **Text Anti-Aliasing**: Whether to show smooth grey edges (anti-aliasing) on text in reading mode. Note this slows down page turns slightly.
-- **Short Power Button Click**: Controls the effect of a short click of the power button:
-  - "Ignore" - Require a long press to turn off the device
-  - "Sleep" - A short press powers the device off
-  - "Page Turn" - A short press in reading mode turns to the next page; a long press turns the device off
+- **Refresh Frequency**: Set how often the screen does a full refresh while reading to reduce ghosting; options are every 1, 5, 10, 15, or 30 pages.
+
+- **UI Theme**: Set which UI theme to use:
+  - "Classic" - The original Crosspoint theme
+  - "Lyra" - The new theme for Crosspoint featuring rounded elements and menu icons
+  - "Lyra Extended" - Lyra, but displays 3 books instead of 1 on the **[Home Screen](#31-home-screen)**
+- **Sunlight Fading Fix**: Configure whether to enable a software-fix for the issue where white X4 models may fade when used in direct sunlight:
+  - "OFF" (default) - Disable the fix
+  - "ON" - Enable the fix
+
+#### 3.6.2 Reader
+- **Reader Font Family**: Choose the font used for reading:
+  - "Bookerly" (default) - Amazon's reading font
+  - "Noto Sans" - Google's sans-serif font
+  - "Open Dyslexic" - Font designed for readers with dyslexia
+- **Reader Font Size**: Adjust the text size for reading; options are "Small", "Medium" (default), "Large", or "X Large".
+
+- **Reader Line Spacing**: Adjust the spacing between lines; options are "Tight", "Normal" (default), or "Wide".
+- **Reader Screen Margin**: Controls the screen margins in Reading Mode between 5 and 40 pixels in 5-pixel increments.
+- **Reader Paragraph Alignment**: Set the alignment of paragraphs; options are "Justified" (default), "Left", "Center", or "Right".
+- **Embedded Style**: Whether to use the EPUB file's embedded HTML and CSS stylisation and formatting; options are "ON" or "OFF".
+- **Hyphenation**: Whether to hyphenate text in Reading Mode; options are "ON" or "OFF".
 - **Reading Orientation**: Set the screen orientation for reading EPUB files:
   - "Portrait" (default) - Standard portrait orientation
   - "Landscape CW" - Landscape, rotated clockwise
   - "Inverted" - Portrait, upside down
   - "Landscape CCW" - Landscape, rotated counter-clockwise
-- **Front Button Layout**: Configure the order of the bottom edge buttons:
-  - Back, Confirm, Left, Right (default)
-  - Left, Right, Back, Confirm
-  - Left, Back, Confirm, Right
-  - Back, Confirm, Right, Left
-- **Side Button Layout (reader)**: Swap the order of the up and down volume buttons from Previous/Next to Next/Previous. This change is only in effect when reading.
-- **Long-press Chapter Skip**: Set whether long-pressing page turn buttons skip to the next/previous chapter.
+- **Extra Paragraph Spacing**: Set how to handle paragraph breaks:
+  - "ON" - Vertical space will be added between paragraphs in Reading Mode
+  - "OFF" - Paragraphs will not have vertical space added, but will have first-line indentation
+- **Text Anti-Aliasing**: Whether to show smooth grey edges (anti-aliasing) on text in reading mode. Note this slows down page turns slightly.
+
+#### 3.6.3 Controls
+
+- **Remap Front Buttons**: A menu for customising the function of each bottom edge button.
+- **Side Button Layout (reader)**: Swap the order of the up and down volume buttons from "Prev/Next" (default) to "Next/Prev". This change is only in effect when reading.
+
+- **Long-press Chapter Skip**: Set whether long-pressing page turn buttons skips to the next/previous chapter:
   - "Chapter Skip" (default) - Long-pressing skips to next/previous chapter
   - "Page Scroll" - Long-pressing scrolls a page up/down
-- Swap the order of the up and down volume buttons from Previous/Next to Next/Previous. This change is only in effect when reading.
-- **Reader Font Family**: Choose the font used for reading:
-  - "Bookerly" (default) - Amazon's reading font
-  - "Noto Sans" - Google's sans-serif font
-  - "Open Dyslexic" - Font designed for readers with dyslexia
-- **Reader Font Size**: Adjust the text size for reading; options are "Small", "Medium", "Large", or "X Large".
-- **Reader Line Spacing**: Adjust the spacing between lines; options are "Tight", "Normal", or "Wide".
-- **Reader Screen Margin**: Controls the screen margins in reader mode between 5 and 40 pixels in 5 pixel increments.
-- **Reader Paragraph Alignment**: Set the alignment of paragraphs; options are "Justified" (default), "Left", "Center", or "Right".
-- **Time to Sleep**: Set the duration of inactivity before the device automatically goes to sleep.
-- **Refresh Frequency**: Set how often the screen does a full refresh while reading to reduce ghosting.
-- **Sunlight Fading Fix**: Configure whether to enable a software-fix for the issue where white X4 models may fade when used in direct sunlight
-  - "OFF" (default) - Disable the fix
-  - "ON" - Enable the fix
+- **Short Power Button Click**: Controls the effect of a short click of the power button:
+  - "Ignore" (default) - Require a long press to turn off the device
+  - "Sleep" - A short press puts the device into sleep mode
+  - "Page Turn" - A short press in reading mode turns to the next page; a long press turns the device off
+
+#### 3.6.4 System
+
+- **Time to Sleep**: Set the duration of inactivity before the device automatically goes to sleep; options are 1, 5, 10 (default), 15 or 30 minutes.
+
+- **WiFi Networks**: Connect to WiFi networks for file transfers and firmware updates.
+- **KOReader Sync**: Options for setting up KOReader for syncing book progress.
 - **OPDS Browser**: Configure OPDS server settings for browsing and downloading books. Set the server URL (for Calibre Content Server, add `/opds` to the end), and optionally configure username and password for servers requiring authentication. Note: Only HTTP Basic authentication is supported. If using Calibre Content Server with authentication enabled, you must set it to use Basic authentication instead of the default Digest authentication.
-- **Check for updates**: Check for firmware updates over WiFi.
+- **Clear Reading Cache**: Clear the internal SD card cache.
+- **Check for updates**: Check for Crosspoint firmware updates over WiFi.
+- **Language**: Set the system language (see **[Supported Languages](#supported-languages)** for more information).
 
-### 3.6 Sleep Screen
+#### 3.6.5 KOReader Sync Quick Setup
 
-You can customize the sleep screen by placing custom images in specific locations on the SD card:
+CrossPoint can sync reading progress with KOReader-compatible sync servers.
+It also interoperates with KOReader apps/devices when they use the same server and credentials.
 
-- **Single Image:** Place a file named `sleep.bmp` in the root directory.
-- **Multiple Images:** Create a `sleep` directory in the root of the SD card and place any number of `.bmp` images inside. If images are found in this directory, they will take priority over the `sleep.bmp` file, and one will be randomly selected each time the device sleeps.
+##### Option A: Free Public Server (`sync.koreader.rocks`)
+
+1. Register a user once (only if needed):
+
+```bash
+USERNAME="user"
+PASSWORD="pass"
+PASSWORD_MD5="$(printf '%s' "$PASSWORD" | openssl md5 | awk '{print $2}')"
+
+curl -i "https://sync.koreader.rocks/users/create" \
+  -H "Accept: application/vnd.koreader.v1+json" \
+  -H "Content-Type: application/json" \
+  --data "{\"username\":\"$USERNAME\",\"password\":\"$PASSWORD_MD5\"}"
+```
+
+Already have KOReader Sync credentials? Skip registration; basic sync only requires using the same existing username/password on all devices.
+
+When this returns `HTTP 402` with `{"code":2002,"message":"Username is already registered."}`, pick a different username or use that existing account.
+
+2. On each CrossPoint device:
+   - Go to **Settings -> System -> KOReader Sync**.
+   - Set **Username** and **Password** (enter the plain password; CrossPoint computes MD5 internally, and use the same values on all devices).
+   - Set **Sync Server URL** to `https://sync.koreader.rocks`, or leave it empty (both use the same default KOReader sync server).
+   - Run **Authenticate**.
+
+3. While reading, press **Confirm** to open the reader menu, then select **Sync Progress**.
+   - Choose **Apply Remote** to jump to remote progress.
+   - Choose **Upload Local** to push current progress.
+
+##### Option B: Self-Hosted Server (Docker Compose)
+
+1. Start a sync server:
+
+```bash
+mkdir -p kosync-quickstart
+cd kosync-quickstart
+
+cat > compose.yaml <<'YAML'
+services:
+  kosync:
+    image: koreader/kosync:latest
+    ports:
+      - "7200:7200"
+      - "17200:17200"
+    volumes:
+      - ./data/redis:/var/lib/redis
+    environment:
+      - ENABLE_USER_REGISTRATION=true
+    restart: unless-stopped
+YAML
+
+# Docker
+docker compose up -d
+
+# Podman (alternative)
+podman compose up -d
+```
 
 > [!NOTE]
-> You'll need to set the **Sleep Screen** setting to **Custom** in order to use these images.
+> `ENABLE_USER_REGISTRATION=true` is convenient for first setup. After creating your users, set it to `false` (or remove it) to avoid unexpected registrations.
+
+2. Verify the server:
+
+```bash
+curl -H "Accept: application/vnd.koreader.v1+json" "http://<server-ip>:17200/healthcheck"
+# Expected: {"state":"OK"}
+```
+
+3. Register a user once.
+CrossPoint authenticates against KOReader Sync (`koreader/kosync`) using an MD5 key, so register using the MD5 of your password:
+
+> [!WARNING]
+> Sending a reusable MD5-derived password over plain HTTP is insecure.
+> Create unique sync-only credentials and do not reuse main account passwords.
+> Prefer `https://<server-ip>:7200` whenever traffic leaves a fully trusted LAN or when using untrusted networks.
+> Use `curl -k` only for self-signed certificate testing.
+
+```bash
+USERNAME="user"
+PASSWORD="pass"
+PASSWORD_MD5="$(printf '%s' "$PASSWORD" | openssl md5 | awk '{print $2}')"
+
+curl -i "http://<server-ip>:17200/users/create" \
+  -H "Accept: application/vnd.koreader.v1+json" \
+  -H "Content-Type: application/json" \
+  --data "{\"username\":\"$USERNAME\",\"password\":\"$PASSWORD_MD5\"}"
+```
+
+If this returns `HTTP 402` with `{"code":2002,"message":"Username is already registered."}`, the account already exists.
+
+4. On each CrossPoint device:
+   - Go to **Settings -> System -> KOReader Sync**.
+   - Set **Username** and **Password** (enter the plain password; CrossPoint computes MD5 internally, and use the same values on all devices).
+   - Set **Sync Server URL** to `http://<server-ip>:17200`.
+   - Run **Authenticate**.
+
+If you use the HTTPS listener, use `https://<server-ip>:7200` (`curl -k` only for self-signed certificate testing).
+
+5. While reading, press **Confirm** to open the reader menu, then select **Sync Progress**.
+   - Choose **Apply Remote** to jump to remote progress.
+   - Choose **Upload Local** to push current progress.
+
+### 3.7 Sleep Screen
+
+The **Sleep Screen** setting controls what is displayed when the device goes to sleep:
+
+| Mode | Behavior |
+|------|----------|
+| **Dark** (default) | The CrossPoint logo on a dark background. |
+| **Light** | The CrossPoint logo on a white background. |
+| **Custom** | A custom image from the SD card (see below). Falls back to **Dark** if no custom image is found. |
+| **Cover** | The cover of the currently open book. Falls back to **Dark** if no book is open. |
+| **Cover + Custom** | The cover of the currently open book. Falls back to **Custom** behavior if no book is open. |
+| **None** | A blank screen. |
+
+#### Cover settings
+
+When using **Cover** or **Cover + Custom**, two additional settings apply:
+
+- **Sleep Screen Cover Mode**: **Fit** (scale to fit, white borders) or **Crop** (scale and crop to fill the screen).
+- **Sleep Screen Cover Filter**: **None** (grayscale), **Contrast** (black & white), or **Inverted** (inverted black & white).
+
+#### Custom images
+
+To use custom sleep images, set the sleep screen mode to **Custom** or **Cover + Custom**, then place images on the SD card:
+
+- **Multiple Images (recommended):** Create a `.sleep` directory in the root of the SD card and place any number of `.bmp` images inside. One will be randomly selected each time the device sleeps. (A directory named `sleep` is also accepted as a fallback.)
+- **Single Image:** Place a file named `sleep.bmp` in the root directory. This is used as a fallback if no valid images are found in the `.sleep`/`sleep` directory.
 
 > [!TIP]
 > For best results:
@@ -188,7 +350,7 @@ Once you have opened a book, the button layout changes to facilitate reading.
 | **Previous Page** | Press **Left** _or_ **Volume Up**    |
 | **Next Page**     | Press **Right** _or_ **Volume Down** |
 
-The role of the volume (side) buttons can be swapped in **[Settings](#35-settings)**.
+The role of the volume (side) buttons can be swapped in the **[Controls Settings](#363-controls)**.
 
 If the **Short Power Button Click** setting is set to "Page Turn", you can also turn to the next page by briefly pressing the Power button.
 
@@ -196,13 +358,13 @@ If the **Short Power Button Click** setting is set to "Page Turn", you can also
 * **Next Chapter:** Press and **hold** the **Right** (or **Volume Down**) button briefly, then release.
 * **Previous Chapter:** Press and **hold** the **Left** (or **Volume Up**) button briefly, then release.
 
-This feature can be disabled in **[Settings](#35-settings)** to help avoid changing chapters by mistake.
+This feature can be disabled in the **[Controls Settings](#363-controls)** to help avoid changing chapters by mistake.
 
 
 ### System Navigation
-* **Return to Book Selection:** Press **Back** to close the book and return to the **[Book Selection](#32-book-selection)** screen.
-* **Return to Home:** Press and **hold** the **Back** button to close the book and return to the **[Home](#31-home-screen)** screen.
-* **Chapter Menu:** Press **Confirm** to open the **[Table of Contents/Chapter Selection](#5-chapter-selection-screen)**.
+* **Return to Home:** Press the **Back** button to close the book and return to the **[Home](#31-home-screen)** screen.
+* **Return to Browse Files:** Press and hold the **Back** button to close the book and return to the **[Browse Files](#33-browse-files-screen)** screen.
+* **Chapter Menu:** Press **Confirm** to open the **[Table of Contents/Chapter Selection](#5-chapter-selection-screen)** screen.
 
 ### Supported Languages
 

bin/clang-format-fix

@@ -1,17 +1,32 @@
 #!/usr/bin/env bash
 
-# Check if clang-format is availible
-command -v clang-format >/dev/null 2>&1 || {
-    printf "'clang-format' not found in current environment\n"
-    printf "install 'clang', 'clang-tools', or 'clang-format' depending on your distro/os and tooling requirements\n"
-    exit 1
-}
+# Check if clang-format is available and pick the preferred binary.
+if command -v clang-format-21 >/dev/null 2>&1; then
+  CLANG_FORMAT_BIN="clang-format-21"
+elif command -v clang-format >/dev/null 2>&1; then
+  CLANG_FORMAT_BIN="clang-format"
+else
+  printf "'clang-format' not found in current environment\n"
+  printf "Install clang-format-21 (recommended), clang, clang-tools, or clang-format depending on your distro/os and tooling requirements\n"
+  exit 1
+fi
+
+set -euo pipefail
 
 GIT_LS_FILES_FLAGS=""
-if [[ "$1" == "-g" ]]; then
+if [[ "${1:-}" == "-g" ]]; then
   GIT_LS_FILES_FLAGS="--modified"
 fi
 
+CLANG_FORMAT_VERSION_RAW="$(${CLANG_FORMAT_BIN} --version)"
+CLANG_FORMAT_MAJOR="$(printf '%s\n' "${CLANG_FORMAT_VERSION_RAW}" | grep -oE '[0-9]+' | head -n1)"
+
+if [[ -z "${CLANG_FORMAT_MAJOR}" || "${CLANG_FORMAT_MAJOR}" -lt 21 ]]; then
+  echo "Error: ${CLANG_FORMAT_BIN} is too old: ${CLANG_FORMAT_VERSION_RAW}"
+  echo "This repository's .clang-format requires clang-format 21 or newer."
+  echo "Install clang-format-21 and rerun ./bin/clang-format-fix"
+  exit 1
+fi
 
 # --- Main Logic ---
 
@@ -27,4 +42,4 @@ git ls-files  --exclude-standard ${GIT_LS_FILES_FLAGS} \
     | grep -v -E '^lib/EpdFont/builtinFonts/' \
     | grep -v -E '^lib/Epub/Epub/hyphenation/generated/' \
     | grep -v -E '^lib/uzlib/' \
-    | xargs -r clang-format -style=file -i
+    | xargs -r "${CLANG_FORMAT_BIN}" -style=file -i

bin/clang-format-fix.ps1

@@ -0,0 +1,154 @@
+<#
+.SYNOPSIS
+    Runs clang-format -i on project *.cpp and *.h files.
+
+.DESCRIPTION
+    Formats all C/C++ source and header files in the repository, excluding
+    generated, vendored, and build directories (open-x4-sdk, builtinFonts,
+    hyphenation tries, uzlib, .pio, *.generated.h).
+
+    The clang-format binary path is resolved once and cached in
+    bin/clang-format-fix.local. On first run it checks a default path,
+    then PATH, then common install locations. Edit the .local file to
+    override manually.
+
+.PARAMETER g
+    Format only git-modified files (git diff --name-only HEAD) instead of
+    the full tree.
+
+.PARAMETER h
+    Show this help text.
+
+.EXAMPLE
+    .\clang-format-fix.ps1
+    Format all files.
+
+.EXAMPLE
+    .\clang-format-fix.ps1 -g
+    Format only git-modified files.
+#>
+
+param(
+    [switch]$g,
+    [switch]$h
+)
+
+if ($h) {
+    Get-Help $PSCommandPath -Detailed
+    return
+}
+
+$repoRoot = (Resolve-Path "$PSScriptRoot\..").Path
+$configFile = Join-Path $PSScriptRoot 'clang-format-fix.local'
+$defaultPath = 'C:\Program Files\LLVM\bin\clang-format.exe'
+
+$candidatePaths = @(
+    'C:\Program Files\LLVM\bin\clang-format.exe'
+    'C:\Program Files (x86)\LLVM\bin\clang-format.exe'
+    'C:\msys64\ucrt64\bin\clang-format.exe'
+    'C:\msys64\mingw64\bin\clang-format.exe'
+    "$env:LOCALAPPDATA\LLVM\bin\clang-format.exe"
+)
+
+function Find-ClangFormat {
+    # Try PATH first
+    $inPath = Get-Command clang-format -ErrorAction SilentlyContinue
+    if ($inPath) { return $inPath.Source }
+
+    # Try candidate paths
+    foreach ($p in $candidatePaths) {
+        if (Test-Path $p) { return $p }
+    }
+    return $null
+}
+
+function Resolve-ClangFormat {
+    # 1. Read from config if present
+    if (Test-Path $configFile) {
+        $saved = (Get-Content $configFile -Raw).Trim()
+        if ($saved -and (Test-Path $saved)) { return $saved }
+        Write-Host "Configured path no longer valid: $saved"
+    }
+
+    # 2. Check default
+    if (Test-Path $defaultPath) {
+        $defaultPath | Set-Content $configFile
+        Write-Host "Saved clang-format path to $configFile"
+        return $defaultPath
+    }
+
+    # 3. Search PATH and candidate locations
+    $found = Find-ClangFormat
+    if ($found) {
+        $found | Set-Content $configFile
+        Write-Host "Found clang-format at $found - saved to $configFile"
+        return $found
+    }
+
+    Write-Error "clang-format not found. Install LLVM or add clang-format to PATH."
+    exit 1
+}
+
+$clangFormat = Resolve-ClangFormat
+
+$exclude = @(
+    'open-x4-sdk'
+    'lib\EpdFont\builtinFonts'
+    'lib\Epub\Epub\hyphenation\generated'
+    'lib\uzlib'
+    '.pio'
+)
+
+function Test-Excluded($fullPath) {
+    foreach ($ex in $exclude) {
+        if ($fullPath -like "*\$ex\*") { return $true }
+    }
+    if ($fullPath -like '*.generated.h') { return $true }
+    return $false
+}
+
+if ($g) {
+    # Only git-modified *.cpp / *.h files
+    # Covers both staged and unstaged changes
+    $files = @(git -C $repoRoot diff --name-only HEAD) +
+             @(git -C $repoRoot diff --name-only --cached) |
+        Sort-Object -Unique |
+        Where-Object { $_ -match '\.(cpp|h)$' } |
+        ForEach-Object { Get-Item (Join-Path $repoRoot $_) -ErrorAction SilentlyContinue } |
+        Where-Object { $_ -and -not (Test-Excluded $_.FullName) }
+} else {
+    $files = Get-ChildItem -Path $repoRoot -Recurse -Include *.cpp, *.h -File |
+        Where-Object { -not (Test-Excluded $_.FullName) }
+}
+
+$files = @($files)
+
+if ($files.Count -eq 0) {
+    Write-Host 'No files to format.'
+    return
+}
+
+Write-Host "Formatting $($files.Count) files..."
+$i = 0
+$changed = 0
+$failures = 0
+foreach ($f in $files) {
+    $i++
+    $rel = $f.FullName.Substring($repoRoot.Length + 1)
+    $hashBefore = (Get-FileHash $f.FullName -Algorithm MD5).Hash
+    & $clangFormat -i $f.FullName
+    if ($LASTEXITCODE -ne 0) {
+        $failures++
+        Write-Host "  [$i/$($files.Count)] $rel (FAILED, exit code $LASTEXITCODE)"
+        continue
+    }
+    $hashAfter = (Get-FileHash $f.FullName -Algorithm MD5).Hash
+    if ($hashBefore -ne $hashAfter) {
+        $changed++
+        Write-Host "  [$i/$($files.Count)] $rel (changed)"
+    } else {
+        Write-Host "  [$i/$($files.Count)] $rel"
+    }
+}
+Write-Host "Done. $changed/$($files.Count) files changed, $failures failed."
+if ($failures -gt 0) { exit 1 }

docs/activity-manager.md

@@ -0,0 +1,472 @@
+# Activity & ActivityManager Migration Guide
+
+This document explains the refactoring from the original per-activity render task model to the centralized `ActivityManager` introduced in [PR #1016](https://github.com/crosspoint-reader/crosspoint-reader/pull/1016). It covers the architectural differences, what changed for activity authors, and the FreeRTOS task and locking model that underpins the system.
+
+## Overview of Changes
+
+| Aspect | Old Model | New Model |
+|--------|-----------|-----------|
+| Render task | One per activity (8KB stack each) | Single shared task in `ActivityManager` |
+| Render mutex | Per-activity `renderingMutex` | Single global mutex in `ActivityManager` |
+| `RenderLock` | Inner class of `Activity` | Standalone class, acquires global mutex |
+| Subactivities | `ActivityWithSubactivity` base class | Activity stack managed by `ActivityManager` |
+| Navigation | Free functions in `main.cpp` | `activityManager.goHome()`, `goToReader()`, etc. |
+| Subactivity results | Callback lambdas stored in parent | `startActivityForResult()` / `setResult()` / `finish()` |
+| `requestUpdate()` | Notifies activity's own render task | Delegates to `ActivityManager` (immediate or deferred) |
+
+## Architecture
+
+### Old Model: Per-Activity Render Tasks
+
+Each activity created its own FreeRTOS render task on entry and destroyed it on exit:
+
+```text
+┌─────────────────────────────────────────────────────────┐
+│ Main Task (Arduino loop)                                │
+│  ┌───────────────────────────────────────────────────┐  │
+│  │ currentActivity->loop()                           │  │
+│  │   ├── handle input                                │  │
+│  │   ├── update state (under RenderLock)             │  │
+│  │   └── requestUpdate()  ──notify──►  Render Task   │  │
+│  │                                      (per-activity)│  │
+│  │                                      8KB stack     │  │
+│  │                                      owns mutex    │  │
+│  └───────────────────────────────────────────────────┘  │
+│                                                         │
+│ ActivityWithSubactivity:                                │
+│  ┌──────────────┐     ┌──────────────┐                  │
+│  │ Parent        │────►│ SubActivity   │                 │
+│  │ (has render   │     │ (has own      │                 │
+│  │  task)        │     │  render task) │                 │
+│  └──────────────┘     └──────────────┘                  │
+└─────────────────────────────────────────────────────────┘
+```
+
+Problems with this approach:
+
+- **8KB per render task**: Each activity allocated an 8KB FreeRTOS stack for its render task, even though only one renders at a time
+- **Dangerous deletion patterns**: `exitActivity()` + `enterNewActivity()` in callbacks led to `delete this` situations where the caller was destroyed while its code was still on the stack
+- **Subactivity coupling**: Parents stored callbacks to child results, creating tight coupling and lifetime hazards
+
+### New Model: Centralized ActivityManager
+
+A single `ActivityManager` owns the render task and manages an activity stack:
+
+```text
+┌──────────────────────────────────────────────────────────┐
+│ Main Task (Arduino loop)                                 │
+│                                                          │
+│  activityManager.loop()                                  │
+│    │                                                     │
+│    ├── currentActivity->loop()                           │
+│    │     ├── handle input                                │
+│    │     ├── update state (under RenderLock)              │
+│    │     └── requestUpdate()                             │
+│    │                                                     │
+│    ├── process pending actions (Push / Pop / Replace)    │
+│    │                                                     │
+│    └── if requestedUpdate: ──notify──► Render Task       │
+│                                         (single, shared) │
+│                                         8KB stack        │
+│                                         global mutex     │
+│                                                          │
+│  Activity Stack:                                         │
+│  ┌──────────┬──────────┬──────────┐    ┌──────────┐     │
+│  │ Home     │ Settings │ Wifi     │    │ Keyboard │     │
+│  │ (stack)  │ (stack)  │ (stack)  │    │ (current)│     │
+│  └──────────┴──────────┴──────────┘    └──────────┘     │
+│   stackActivities[]                    currentActivity   │
+└──────────────────────────────────────────────────────────┘
+```
+
+## Migration Checklist
+
+### 1. Change Base Class
+
+If your activity extended `ActivityWithSubactivity`, change it to extend `Activity`:
+
+```cpp
+// BEFORE
+class MyActivity final : public ActivityWithSubactivity {
+  MyActivity(GfxRenderer& r, MappedInputManager& m, std::function<void()> goBack)
+      : ActivityWithSubactivity("MyActivity", r, m), goBack(goBack) {}
+};
+
+// AFTER
+class MyActivity final : public Activity {
+  MyActivity(GfxRenderer& r, MappedInputManager& m)
+      : Activity("MyActivity", r, m) {}
+};
+```
+
+Note that navigation callbacks like `goBack` are no longer stored — use `finish()` or `activityManager.goHome()` instead.
+
+### 2. Replace Navigation Functions
+
+The free functions `exitActivity()` / `enterNewActivity()` in `main.cpp` are gone. Use `ActivityManager` methods:
+
+```cpp
+// BEFORE (in main.cpp or via stored callbacks)
+exitActivity();
+enterNewActivity(new SettingsActivity(renderer, mappedInput, onGoHome));
+
+// AFTER (from any Activity method)
+activityManager.goToSettings();
+// or for arbitrary navigation:
+activityManager.replaceActivity(std::make_unique<MyActivity>(renderer, mappedInput));
+```
+
+`replaceActivity()` destroys the current activity and clears the stack. Use it for top-level navigation (home, reader, settings, etc.).
+
+### 3. Replace Subactivity Pattern
+
+The `enterNewActivity()` / `exitActivity()` subactivity pattern is replaced by a stack with typed results:
+
+```cpp
+// BEFORE
+void MyActivity::launchWifi() {
+  enterNewActivity(new WifiSelectionActivity(renderer, mappedInput,
+      [this](bool connected) { onWifiDone(connected); }));
+}
+// Child calls: onComplete(true); // triggers callback, which may call exitActivity()
+
+// AFTER
+void MyActivity::launchWifi() {
+  startActivityForResult(
+      std::make_unique<WifiSelectionActivity>(renderer, mappedInput),
+      [this](const ActivityResult& result) {
+        if (result.isCancelled) return;
+        auto& wifi = std::get<WifiResult>(result.data);
+        onWifiDone(wifi.connected);
+      });
+}
+// Child calls:
+//   setResult(WifiResult{.connected = true, .ssid = ssid});
+//   finish();
+```
+
+Key differences:
+
+- **`startActivityForResult()`** pushes the current activity onto the stack and launches the child
+- **`setResult()`** stores a typed result on the child activity
+- **`finish()`** signals the manager to pop the child, call the result handler, and resume the parent
+- The parent is never deleted during this process — it's safely stored on the stack
+
+### 4. Update `render()` Signature
+
+The `RenderLock` type changed from `Activity::RenderLock` (inner class) to standalone `RenderLock`:
+
+```cpp
+// BEFORE
+void render(Activity::RenderLock&&) override;
+
+// AFTER
+void render(RenderLock&&) override;
+```
+
+Include `RenderLock.h` if not transitively included via `Activity.h`.
+
+### 5. Update `onEnter()` / `onExit()`
+
+Activities no longer create or destroy render tasks:
+
+```cpp
+// BEFORE
+void MyActivity::onEnter() {
+  Activity::onEnter();       // created render task + logged
+  // ... allocate resources
+  requestUpdate();
+}
+void MyActivity::onExit() {
+  // ... free resources
+  Activity::onExit();        // acquired RenderLock, deleted render task
+}
+
+// AFTER
+void MyActivity::onEnter() {
+  Activity::onEnter();       // just logs
+  // ... allocate resources
+  requestUpdate();
+}
+void MyActivity::onExit() {
+  // ... free resources
+  Activity::onExit();        // just logs
+}
+```
+
+The render task lifecycle is handled entirely by `ActivityManager::begin()`.
+
+### 6. Update `requestUpdate()` Calls
+
+The signature changed to accept an `immediate` flag:
+
+```cpp
+// BEFORE
+void requestUpdate();  // always immediate notification to per-activity render task
+
+// AFTER
+void requestUpdate(bool immediate = false);
+// immediate=false (default): deferred until end of current loop iteration
+// immediate=true: sends notification to render task right away
+```
+
+**When to use `immediate`**: Almost never. Deferred updates are batched — if `loop()` triggers multiple state changes that each call `requestUpdate()`, only one render happens. Use `immediate` only when you need the render to start before the current function returns (e.g., before a blocking network call).
+
+**`requestUpdateAndWait()`**: Blocks the calling task until the render completes. Use sparingly — it's designed for cases where you need the screen to reflect new state before proceeding (e.g., showing "Checking for update..." before calling a network API).
+
+### 7. Remove Stored Navigation Callbacks
+
+Old activities often stored `std::function` callbacks for navigation:
+
+```cpp
+// BEFORE
+class SettingsActivity : public ActivityWithSubactivity {
+  const std::function<void()> goBack;   // stored callback
+  const std::function<void()> goHome;   // stored callback
+public:
+  SettingsActivity(GfxRenderer& r, MappedInputManager& m,
+                   std::function<void()> goBack, std::function<void()> goHome)
+      : ActivityWithSubactivity("Settings", r, m), goBack(goBack), goHome(goHome) {}
+};
+
+// AFTER
+class SettingsActivity : public Activity {
+public:
+  SettingsActivity(GfxRenderer& r, MappedInputManager& m)
+      : Activity("Settings", r, m) {}
+  // Use finish() to go back, activityManager.goHome() to go home
+};
+```
+
+This removes `std::function` overhead (~2-4KB per unique signature) and eliminates lifetime risks from captured `this` pointers.
+
+## Technical Details
+
+### FreeRTOS Task Model
+
+The firmware runs on an ESP32-C3, a single-core RISC-V microcontroller. FreeRTOS provides cooperative and preemptive multitasking on this single core — only one task executes at any moment, and the scheduler switches between tasks at yield points (blocking calls, `vTaskDelay`, `taskYIELD`) or when a tick interrupt promotes a higher-priority task.
+
+There are two tasks relevant to the activity system:
+
+```text
+┌──────────────────────┐     ┌──────────────────────────┐
+│ Main Task            │     │ Render Task              │
+│ (Arduino loop)       │     │ (ActivityManager-owned)   │
+│ Priority: 1          │     │ Priority: 1              │
+│                      │     │                          │
+│ Runs:                │     │ Runs:                    │
+│ - gpio.update()      │     │ - ulTaskNotifyTake()     │
+│ - activity->loop()   │     │   (blocks until notified)│
+│ - pending actions    │     │ - RenderLock (mutex)     │
+│ - sleep/power mgmt   │     │ - activity->render()     │
+│ - requestUpdate →────┼─────┼─► xTaskNotify()          │
+│   (end of loop)      │     │                          │
+└──────────────────────┘     └──────────────────────────┘
+```
+
+Both tasks run at priority 1. Since the ESP32-C3 is single-core, they alternate execution: the main task runs `loop()`, then at the end of the loop iteration, notifies the render task if an update was requested. The render task wakes, acquires the mutex, calls `render()`, releases the mutex, and blocks again.
+
+Do not use `xTaskCreate` inside activities. If you have a use case that seems to require a background task, open a discussion to propose a lifecycle-aware `Worker` abstraction first.
+
+### The Render Mutex and RenderLock
+
+A single FreeRTOS mutex (`renderingMutex`) protects shared state between `loop()` and `render()`. Since these run on different tasks, any state read by `render()` and written by `loop()` must be guarded.
+
+`RenderLock` is an RAII wrapper:
+
+```cpp
+// Standalone class (not tied to any specific activity)
+class RenderLock {
+  bool isLocked = false;
+public:
+  explicit RenderLock();           // acquires activityManager.renderingMutex
+  explicit RenderLock(Activity&);  // same — Activity& param kept for compatibility
+  ~RenderLock();                   // releases mutex if still held
+  void unlock();                   // early release
+};
+```
+
+**Usage patterns:**
+
+```cpp
+// In loop(): protect state mutations that render() reads
+void MyActivity::loop() {
+  if (somethingChanged) {
+    RenderLock lock;
+    state = newState;        // safe — render() can't run while lock is held
+  }
+  requestUpdate();           // trigger render after lock is released
+}
+
+// In render(): lock is passed in, held for duration of render
+void MyActivity::render(RenderLock&&) {
+  // Lock is held — safe to read shared state
+  renderer.clearScreen();
+  renderer.drawText(..., stateString, ...);
+  renderer.displayBuffer();
+  // Lock released when RenderLock destructor runs
+}
+```
+
+**Critical rule**: Never call `requestUpdateAndWait()` while holding a `RenderLock`. The render task needs the mutex to call `render()`, so holding it while waiting for the render to complete is a deadlock:
+
+```text
+Main Task                    Render Task
+──────────                   ───────────
+RenderLock lock;             (blocked on mutex)
+requestUpdateAndWait();
+  → notify render task
+  → block waiting for
+    render to complete        → wakes up
+                              → tries to acquire mutex
+                              → DEADLOCK: main holds mutex,
+                                waits for render; render
+                                waits for mutex
+```
+
+### requestUpdate() vs requestUpdateAndWait()
+
+```text
+requestUpdate(false)          requestUpdate(true)
+─────────────────             ─────────────────
+Sets flag only.               Notifies render task
+Render happens after          immediately.
+loop() returns and            Render may start
+ActivityManager checks        before the calling
+the flag.                     function returns.
+                              (Does NOT wait for
+                              render to complete.)
+
+requestUpdateAndWait()
+──────────────────────
+Notifies render task AND
+blocks calling task until
+render is done. Uses
+FreeRTOS direct-to-task
+notification on the
+caller's task handle.
+```
+
+`requestUpdateAndWait()` flow in detail:
+
+```text
+Calling Task                 Render Task
+────────────                 ───────────
+requestUpdateAndWait()
+  ├─ assert: not render task
+  ├─ assert: not holding RenderLock
+  ├─ store waitingTaskHandle
+  ├─ xTaskNotify(renderTask)  → wakes render task
+  └─ ulTaskNotifyTake() ─┐
+     (blocked)           │    RenderLock lock;
+                         │    activity->render();
+                         │    // render complete
+                         │    taskENTER_CRITICAL
+                         │    waiter = waitingTaskHandle
+                         │    waitingTaskHandle = nullptr
+                         │    taskEXIT_CRITICAL
+                         │    xTaskNotify(waiter) ───┐
+                         │                           │
+  ┌──────────────────────┘                           │
+  │ (woken by notification) ◄────────────────────────┘
+  └─ return
+```
+
+### Activity Lifecycle Under ActivityManager
+
+```text
+activityManager.replaceActivity(make_unique<MyActivity>(...))
+  │
+  ▼
+╔═══════════════════════════════════════════════════╗
+║  pendingAction = Replace                          ║
+║  pendingActivity = MyActivity                     ║
+╚═══════════════════════════════════════════════════╝
+  │
+  ▼ (next loop iteration)
+  ActivityManager::loop()
+  │
+  ├── currentActivity->loop()     // old activity's last loop
+  │
+  ├── process pending action:
+  │   ├── RenderLock lock;
+  │   ├── oldActivity->onExit()   // cleanup under lock
+  │   ├── delete oldActivity
+  │   ├── clear stack
+  │   ├── currentActivity = MyActivity
+  │   ├── lock.unlock()
+  │   └── MyActivity->onEnter()   // init new activity
+  │
+  └── if requestedUpdate:
+      └── notify render task
+```
+
+For push/pop (subactivity) navigation:
+
+```text
+Parent calls: startActivityForResult(make_unique<Child>(...), handler)
+  │
+  ▼
+╔══════════════════════════════════════╗
+║  pendingAction = Push               ║
+║  pendingActivity = Child            ║
+║  parent->resultHandler = handler    ║
+╚══════════════════════════════════════╝
+  │
+  ▼ (next loop iteration)
+  ├── Parent moved to stackActivities[]
+  ├── currentActivity = Child
+  └── Child->onEnter()
+
+        ... child runs ...
+
+Child calls: setResult(MyResult{...}); finish();
+  │
+  ▼
+╔══════════════════════════════════════╗
+║  pendingAction = Pop                ║
+║  child->result = MyResult{...}      ║
+╚══════════════════════════════════════╝
+  │
+  ▼ (next loop iteration)
+  ├── result = child->result
+  ├── Child->onExit(); delete Child
+  ├── currentActivity = Parent (popped from stack)
+  ├── Parent->resultHandler(result)
+  └── requestUpdate()   // automatic re-render for parent
+```
+
+### Common Pitfalls
+
+**Calling `finish()` and continuing to access `this`**: `finish()` sets `pendingAction = Pop` but does not immediately destroy the activity. The activity is destroyed on the next `ActivityManager::loop()` iteration. It's safe to access member variables after `finish()` within the same function, but don't rely on the activity surviving past the current `loop()` call.
+
+**Modifying shared state without `RenderLock`**: If `render()` reads a variable and `loop()` writes it, the write must be under a `RenderLock`. Without it, `render()` could see a half-written value (e.g., a partially updated string or struct).
+
+**Creating background tasks that outlive the activity**: Any FreeRTOS task created in `onEnter()` must be deleted in `onExit()` before the activity is destroyed. The `ActivityManager` does not track or clean up background tasks.
+
+**Holding `RenderLock` across blocking calls**: The render task is blocked on the mutex while you hold the lock. Keep critical sections short — acquire, mutate state, release, then do blocking work.
+
+```cpp
+// WRONG — blocks render for the entire network call
+void MyActivity::doNetworkStuff() {
+  RenderLock lock;
+  state = LOADING;
+  auto result = http.get(url);  // blocks for seconds with lock held
+  state = DONE;
+}
+
+// CORRECT — release lock before blocking
+void MyActivity::doNetworkStuff() {
+  {
+    RenderLock lock;
+    state = LOADING;
+  }
+  requestUpdate(true);           // render "Loading..." immediately, before we block
+  auto result = http.get(url);   // lock is not held
+  {
+    RenderLock lock;
+    state = DONE;
+  }
+  requestUpdate();
+}
+```

docs/contributing/README.md

@@ -0,0 +1,11 @@
+# Contributing Docs
+
+This section is a lightweight contributor guide for CrossPoint Reader.
+It is written for software developers who may be new to embedded development.
+
+- [Getting Started](./getting-started.md)
+- [Architecture Overview](./architecture.md)
+- [Development Workflow](./development-workflow.md)
+- [Testing and Debugging](./testing-debugging.md)
+
+If you are new, start with [Getting Started](./getting-started.md).

docs/contributing/architecture.md

@@ -0,0 +1,199 @@
+# Architecture Overview
+
+CrossPoint is firmware for the Xteink X4 (unaffiliated with Xteink), built with PlatformIO targeting the ESP32-C3 microcontroller.
+
+At a high level, it is firmware that uses an activity-driven application architecture loop with persistent settings/state, SD-card-first caching, and a rendering pipeline optimized for e-ink constraints.
+
+## System at a glance
+
+```mermaid
+graph TD
+    A[Hardware: ESP32-C3 + SD + E-ink + Buttons] --> B[open-x4-sdk HAL]
+    B --> C[src/main.cpp runtime loop]
+    C --> D[Activities layer]
+    C --> E[State and settings]
+    D --> F[Reader flows]
+    D --> G[Home/Library/Settings flows]
+    D --> H[Network/Web server flows]
+    F --> I[lib/Epub parsing + layout + hyphenation]
+    I --> J[SD cache in .crosspoint]
+    D --> K[GfxRenderer]
+    K --> L[E-ink display buffer]
+```
+
+## Runtime lifecycle
+
+Primary entry point is `src/main.cpp`.
+
+```mermaid
+flowchart TD
+    A[Boot] --> B[Init GPIO and optional serial]
+    B --> C[Init SD storage]
+    C --> D[Load settings and app state]
+    D --> E[Init display and fonts]
+    E --> F{Resume reader?}
+    F -->|No| G[Enter Home activity]
+    F -->|Yes| H[Enter Reader activity]
+    G --> I[Main loop]
+    H --> I
+    I --> J[Poll input and run current activity]
+    J --> K{Sleep condition met?}
+    K -->|No| I
+    K -->|Yes| L[Persist state and enter deep sleep]
+```
+
+In each loop iteration, the firmware updates input, runs the active activity, handles auto-sleep/power behavior, and applies a short delay policy to balance responsiveness and power.
+
+## Activity model
+
+Activities are screen-level controllers deriving from `src/activities/Activity.h`.
+Some flows use `src/activities/ActivityWithSubactivity.h` to host nested activities.
+
+- `onEnter()` and `onExit()` manage setup/teardown
+- `loop()` handles per-frame behavior
+- `skipLoopDelay()` and `preventAutoSleep()` are used by long-running flows (for example web server mode)
+
+Top-level activity groups:
+
+- `src/activities/home/`: home and library navigation
+- `src/activities/reader/`: EPUB/XTC/TXT reading flows
+- `src/activities/settings/`: settings menus and configuration
+- `src/activities/network/`: WiFi selection, AP/STA mode, file transfer server
+- `src/activities/boot_sleep/`: boot and sleep transitions
+
+## Reader and content pipeline
+
+Reader orchestration starts in `src/activities/reader/ReaderActivity.h` and dispatches to format-specific readers.
+EPUB processing is implemented in `lib/Epub/`.
+
+```mermaid
+flowchart LR
+    A[Select book] --> B[ReaderActivity]
+    B --> C{Format}
+    C -->|EPUB| D[lib/Epub/Epub]
+    C -->|XTC| E[lib/Xtc reader]
+    C -->|TXT| F[lib/Txt reader]
+    D --> G[Parse OPF/TOC/CSS]
+    G --> H[Layout pages/sections]
+    H --> I[Write section and metadata caches]
+    I --> J[Render current page via GfxRenderer]
+```
+
+Why caching matters:
+
+- RAM is limited on ESP32-C3, so expensive parsed/layout data is persisted to SD
+- repeat opens/page navigation can reuse cached data instead of full reparsing
+
+## Reader internals call graph
+
+This diagram zooms into the EPUB path to show the main control and data flow from activity entry to on-screen draw.
+
+```mermaid
+flowchart TD
+    A[ReaderActivity onEnter] --> B{File type}
+    B -->|EPUB| C[Create Epub object]
+    B -->|XTC/TXT| Z[Use format-specific reader]
+
+    C --> D[Epub load]
+    D --> E[Locate container and OPF]
+    E --> F[Build or load BookMetadataCache]
+    F --> G[Load TOC and spine]
+    G --> H[Load or parse CSS rules]
+
+    H --> I[EpubReaderActivity]
+    I --> J{Section cache exists for current settings?}
+    J -->|Yes| K[Read section bin from SD cache]
+    J -->|No| L[Parse chapter HTML and layout text]
+    L --> M[Apply typography settings and hyphenation]
+    M --> N[Write section cache bin]
+
+    K --> O[Build page model]
+    N --> O
+    O --> P[GfxRenderer draw calls]
+    P --> Q[HAL display framebuffer update]
+    Q --> R[E-ink refresh policy]
+
+    S[SETTINGS singleton] -. influences .-> J
+    S -. influences .-> M
+    T[APP_STATE singleton] -. persists .-> U[Reading progress and resume context]
+    U -. used by .-> I
+```
+
+Notes:
+
+- "section cache exists" depends on cache-busting parameters such as font and layout-related settings
+- rendering favors reusing precomputed layout data to keep page turns responsive on constrained hardware
+- progress/session state is persisted so the reader can reopen at the last position after reboot/sleep
+
+## State and persistence
+
+Two singletons are central:
+
+- `src/CrossPointSettings.h` (`SETTINGS`): user preferences and behavior flags
+- `src/CrossPointState.h` (`APP_STATE`): runtime/session state such as current book and sleep context
+
+Typical persisted areas on SD:
+
+```text
+/.crosspoint/
+  epub_<hash>/
+    book.bin
+    progress.bin
+    cover.bmp
+    sections/*.bin
+  settings.bin
+  state.bin
+```
+
+For binary cache formats, see `docs/file-formats.md`.
+
+## Networking architecture
+
+Network file transfer is controlled by `src/activities/network/CrossPointWebServerActivity.h` and served by `src/network/CrossPointWebServer.h`.
+
+Modes:
+
+- STA: join existing WiFi network
+- AP: create hotspot
+
+Server behavior:
+
+- HTTP server on port 80
+- WebSocket upload server on port 81
+- file operations backed by SD storage
+- activity requests faster loop responsiveness while server is running
+
+Endpoint reference: `docs/webserver-endpoints.md`.
+
+## Build-time generated assets
+
+Some sources are generated and should not be edited manually.
+
+- `scripts/build_html.py` generates `src/network/html/*.generated.h` from HTML files
+- `scripts/generate_hyphenation_trie.py` generates hyphenation headers under `lib/Epub/Epub/hyphenation/generated/`
+
+When editing related source assets, regenerate via normal build steps/scripts.
+
+## Key directories
+
+- `src/`: app orchestration, settings/state, and activity implementations
+- `src/network/`: web server and OTA/update networking
+- `src/components/`: theming and shared UI components
+- `lib/Epub/`: EPUB parser, layout, CSS handling, and hyphenation
+- `lib/`: supporting libraries (fonts, text, filesystem helpers, etc.)
+- `open-x4-sdk/`: hardware SDK submodule (display, input, storage, battery)
+- `docs/`: user and technical documentation
+
+## Embedded constraints that shape design
+
+- constrained RAM drives SD-first caching and careful allocations
+- e-ink refresh cost drives render/update batching choices
+- main loop responsiveness matters for input, power handling, and watchdog safety
+- background/network flows must cooperate with sleep and loop timing logic
+
+## Scope guardrails
+
+Before implementing larger ideas, check:
+
+- [SCOPE.md](../../SCOPE.md)
+- [GOVERNANCE.md](../../GOVERNANCE.md)

docs/contributing/development-workflow.md

@@ -0,0 +1,43 @@
+# Development Workflow
+
+This page defines the expected local workflow before opening a pull request.
+
+## 1) Fork and create a focused branch
+
+- Fork the repository to your own GitHub account
+- Clone your fork locally and add the upstream repository if needed
+
+- Branch from `master`
+- Keep each PR focused on one fix or feature area
+
+## 2) Implement with scope in mind
+
+- Confirm your idea is in project scope: [SCOPE.md](../../SCOPE.md)
+- Prefer incremental changes over broad refactors
+
+## 3) Run local checks
+
+```sh
+./bin/clang-format-fix
+pio check --fail-on-defect low --fail-on-defect medium --fail-on-defect high
+pio run
+```
+
+CI enforces formatting, static analysis, and build checks.
+Use clang-format 21+ locally to match CI.
+If `clang-format` is missing or too old locally, see [Getting Started](./getting-started.md).
+
+## 4) Open the PR
+
+- Use a semantic title (example: `fix: avoid crash when opening malformed epub`)
+- Fill out `.github/PULL_REQUEST_TEMPLATE.md`
+- Describe the problem, approach, and any tradeoffs
+- Include reproduction and verification steps for bug fixes
+
+## 5) Review etiquette
+
+- Be explicit and concise in responses
+- Keep discussions technical and respectful
+- Assume good intent and focus on code-level feedback
+
+For community expectations, see [GOVERNANCE.md](../../GOVERNANCE.md).

docs/contributing/getting-started.md

@@ -0,0 +1,80 @@
+# Getting Started
+
+This guide helps you build and run CrossPoint locally.
+
+## Prerequisites
+
+- PlatformIO Core (`pio`) or VS Code + PlatformIO IDE
+- Python 3.8+
+- `clang-format` 21+ in your `PATH` (CI uses clang-format 21)
+- USB-C cable
+- Xteink X4 device for hardware testing
+
+If `./bin/clang-format-fix` fails with either of these errors, install clang-format 21:
+
+- `clang-format: No such file or directory`
+- `.clang-format: error: unknown key 'AlignFunctionDeclarations'`
+
+Examples:
+
+```sh
+# Debian/Ubuntu (try this first)
+sudo apt-get update && sudo apt-get install -y clang-format-21
+
+# If the package is unavailable, add LLVM apt repo and retry
+wget https://apt.llvm.org/llvm.sh
+chmod +x llvm.sh
+sudo ./llvm.sh 21
+sudo apt-get update
+sudo apt-get install -y clang-format-21
+
+# macOS (Homebrew)
+brew install clang-format
+```
+
+Then verify:
+
+```sh
+clang-format-21 --version
+```
+
+The reported major version must be 21 or newer.
+
+## Clone and initialize
+
+```sh
+git clone --recursive https://github.com/crosspoint-reader/crosspoint-reader
+cd crosspoint-reader
+```
+
+If you already cloned without submodules:
+
+```sh
+git submodule update --init --recursive
+```
+
+## Build
+
+```sh
+pio run
+```
+
+## Flash
+
+```sh
+pio run --target upload
+```
+
+## First checks before opening a PR
+
+```sh
+./bin/clang-format-fix
+pio check --fail-on-defect low --fail-on-defect medium --fail-on-defect high
+pio run
+```
+
+## What to read next
+
+- [Architecture Overview](./architecture.md)
+- [Development Workflow](./development-workflow.md)
+- [Testing and Debugging](./testing-debugging.md)

docs/contributing/testing-debugging.md

@@ -0,0 +1,48 @@
+# Testing and Debugging
+
+CrossPoint runs on real hardware, so debugging usually combines local build checks and on-device logs.
+
+## Local checks
+
+Make sure `clang-format` 21+ is installed and available in `PATH` before running the formatting step.
+If needed, see [Getting Started](./getting-started.md).
+
+```sh
+./bin/clang-format-fix
+pio check --fail-on-defect low --fail-on-defect medium --fail-on-defect high
+pio run
+```
+
+## Flash and monitor
+
+Flash firmware:
+
+```sh
+pio run --target upload
+```
+
+Open serial monitor:
+
+```sh
+pio device monitor
+```
+
+Optional enhanced monitor:
+
+```sh
+python3 -m pip install pyserial colorama matplotlib
+python3 scripts/debugging_monitor.py
+```
+
+## Useful bug report contents
+
+- Firmware version and build environment
+- Exact steps to reproduce
+- Expected vs actual behavior
+- Serial logs from boot through failure
+- Whether issue reproduces after clearing `.crosspoint/` cache on SD card
+
+## Common troubleshooting references
+
+- [User Guide troubleshooting section](../../USER_GUIDE.md#7-troubleshooting-issues--escaping-bootloop)
+- [Webserver troubleshooting](../troubleshooting.md)

docs/i18n.md

@@ -12,6 +12,10 @@ This guide explains the multi-language support system in CrossPoint Reader.
 - Swedish
 - Czech
 - Russian
+- Ukrainian
+- Polish
+- Danish
+- Turkish
 
 ---
 
@@ -51,7 +55,7 @@ A file looks like this:
 
 ```yaml
 _language_name: "Español"
-_language_code: "SPANISH"
+_language_code: "ES"
 _order: "1"
 
 STR_CROSSPOINT: "CrossPoint"
@@ -61,13 +65,13 @@ STR_BROWSE_FILES: "Buscar archivos"
 
 **Metadata keys** (prefixed with `_`):
 - `_language_name` — Native display name shown to the user (e.g. "Français")
-- `_language_code` — C++ enum name (e.g. "FRENCH"). Must be a valid C++ identifier.
+- `_language_code` — C++ enum name (e.g. "FR"). Please use the [ISO Code](https://en.wikipedia.org/wiki/List_of_ISO_639_language_codes) of the language. Must be a valid C++ identifier.
 - `_order` — Controls the position in the Language enum (English is always 0)
 
 **Rules:**
 - Use UTF-8 encoding
 - Every line must follow the format: `KEY: "value"`
-- Keys must be valid C++ identifiers (uppercase, strats with STR_)
+- Keys must be valid C++ identifiers (uppercase, starts with STR_)
 - Keys must be unique within a file
 - String values must be quoted
 - Use `\n` for newlines, `\\` for literal backslashes, `\"` for literal quotes inside values
@@ -127,7 +131,7 @@ Create `lib/I18n/translations/italian.yaml`:
 
 ```yaml
 _language_name: "Italiano"
-_language_code: "ITALIAN"
+_language_code: "IT"
 _order: "7"
 
 STR_CROSSPOINT: "CrossPoint"
@@ -174,7 +178,7 @@ renderer.drawText(font, x, y, tr(STR_BROWSE_FILES));
 Serial.printf("Status: %s\n", tr(STR_CONNECTED));
 
 // I18N - Shorthand for I18n::getInstance()
-I18N.setLanguage(Language::SPANISH);
+I18N.setLanguage(Language::ES);
 Language lang = I18N.getLanguage();
 
 // === Full API ===
@@ -188,7 +192,7 @@ const char* text = I18N.get(StrId::STR_SETTINGS_TITLE);   // Direct call
 const char* text = I18N[StrId::STR_SETTINGS_TITLE];       // Operator overload
 
 // Set language
-I18N.setLanguage(Language::SPANISH);
+I18N.setLanguage(Language::ES);
 
 // Get current language
 Language lang = I18N.getLanguage();
@@ -200,7 +204,7 @@ I18N.saveSettings();
 I18N.loadSettings();
 
 // Get character set for font subsetting (static method)
-const char* chars = I18n::getCharacterSet(Language::FRENCH);
+const char* chars = I18n::getCharacterSet(Language::FR);
 ```
 
 ---

docs/translators.md

@@ -1,6 +1,6 @@
 # Translators
 
-Below is a list of users and languages CrossPoint may support in the future. 
+Below is a list of users and languages CrossPoint may support in the future.
 Note because a language is below does not mean there is official support for the language at this time.
 
 ## Contributing
@@ -20,7 +20,11 @@ If you'd like to add your name to this list, please open a PR adding yourself an
 ## Portuguese (Brazil)
 - [yagofarias](https://github.com/yagofarias)
 
+## Portuguese (Portugal)
+- [victordomingos](https://github.com/victordomingos)
+
 ## Italian
+- [andreaturchet](https://github.com/andreaturchet)
 - [fragolinux](https://github.com/fragolinux)
 
 ## Russian
@@ -31,6 +35,26 @@ If you'd like to add your name to this list, please open a PR adding yourself an
 - [yeyeto2788](https://github.com/yeyeto2788)
 - [Skrzakk](https://github.com/Skrzakk)
 - [pablohc](https://github.com/pablohc)
+- [DaniPhii](https://github.com/DaniPhii)
 
 ## Swedish
 - [dawiik](https://github.com/dawiik)
+- [steka](https://github.com/steka)
+
+## Romanian
+- [ariel-lindemann](https://github.com/ariel-lindemann)
+
+## Catalan
+- [angeldenom](https://github.com/angeldenom)
+
+## Finnish
+- [plahteenlahti](https://github.com/plahteenlahti)
+
+## Ukrainian
+- [mirus-ua](https://github.com/mirus-ua)
+
+## Belarusian
+- [Dexif](https://github.com/dexif)
+
+## Danish
+- [hajisan](https://github.com/hajisan)

include/README

@@ -1,37 +0,0 @@
-
-This directory is intended for project header files.
-
-A header file is a file containing C declarations and macro definitions
-to be shared between several project source files. You request the use of a
-header file in your project source file (C, C++, etc) located in `src` folder
-by including it, with the C preprocessing directive `#include'.
-
-```src/main.c
-
-#include "header.h"
-
-int main (void)
-{
- ...
-}
-```
-
-Including a header file produces the same results as copying the header file
-into each source file that needs it. Such copying would be time-consuming
-and error-prone. With a header file, the related declarations appear
-in only one place. If they need to be changed, they can be changed in one
-place, and programs that include the header file will automatically use the
-new version when next recompiled. The header file eliminates the labor of
-finding and changing all the copies as well as the risk that a failure to
-find one copy will result in inconsistencies within a program.
-
-In C, the convention is to give header files names that end with `.h'.
-
-Read more about using header files in official GCC documentation:
-
-* Include Syntax
-* Include Operation
-* Once-Only Headers
-* Computed Includes
-
-https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

lib/EpdFont/EpdFont.cpp

@@ -15,37 +15,41 @@ void EpdFont::getTextBounds(const char* string, const int startX, const int star
     return;
   }
 
-  int cursorX = startX;
-  const int cursorY = startY;
+  int32_t cursorXFP = fp4::fromPixel(startX);  // 12.4 fixed-point accumulator
   int lastBaseX = startX;
-  int lastBaseAdvance = 0;
+  int lastBaseAdvanceFP = 0;  // 12.4 fixed-point
   int lastBaseTop = 0;
-  bool hasBaseGlyph = false;
   constexpr int MIN_COMBINING_GAP_PX = 1;
   uint32_t cp;
+  uint32_t prevCp = 0;
   while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&string)))) {
-    const EpdGlyph* glyph = getGlyph(cp);
+    const bool isCombining = utf8IsCombiningMark(cp);
 
-    if (!glyph) {
-      glyph = getGlyph(REPLACEMENT_GLYPH);
+    if (!isCombining) {
+      cp = applyLigatures(cp, string);
     }
 
+    const EpdGlyph* glyph = getGlyph(cp);
     if (!glyph) {
-      // TODO: Better handle this?
+      prevCp = 0;
       continue;
     }
 
-    const bool isCombining = utf8IsCombiningMark(cp);
     int raiseBy = 0;
-    if (isCombining && hasBaseGlyph) {
+    if (isCombining) {
       const int currentGap = glyph->top - glyph->height - lastBaseTop;
       if (currentGap < MIN_COMBINING_GAP_PX) {
         raiseBy = MIN_COMBINING_GAP_PX - currentGap;
       }
     }
 
-    const int glyphBaseX = (isCombining && hasBaseGlyph) ? (lastBaseX + lastBaseAdvance / 2) : cursorX;
-    const int glyphBaseY = cursorY - raiseBy;
+    if (!isCombining && prevCp != 0) {
+      cursorXFP += getKerning(prevCp, cp);  // 4.4 fixed-point kern
+    }
+
+    const int cursorXPixels = fp4::toPixel(cursorXFP);  // snap 12.4 fixed-point to nearest pixel
+    const int glyphBaseX = isCombining ? (lastBaseX + fp4::toPixel(lastBaseAdvanceFP / 2)) : cursorXPixels;
+    const int glyphBaseY = startY - raiseBy;
 
     *minX = std::min(*minX, glyphBaseX + glyph->left);
     *maxX = std::max(*maxX, glyphBaseX + glyph->left + glyph->width);
@@ -53,11 +57,11 @@ void EpdFont::getTextBounds(const char* string, const int startX, const int star
     *maxY = std::max(*maxY, glyphBaseY + glyph->top);
 
     if (!isCombining) {
-      lastBaseX = cursorX;
-      lastBaseAdvance = glyph->advanceX;
+      lastBaseX = cursorXPixels;
+      lastBaseAdvanceFP = glyph->advanceX;  // 12.4 fixed-point
       lastBaseTop = glyph->top;
-      hasBaseGlyph = true;
-      cursorX += glyph->advanceX;
+      cursorXFP += glyph->advanceX;  // 12.4 fixed-point advance
+      prevCp = cp;
     }
   }
 }
@@ -71,30 +75,99 @@ void EpdFont::getTextDimensions(const char* string, int* w, int* h) const {
   *h = maxY - minY;
 }
 
-const EpdGlyph* EpdFont::getGlyph(const uint32_t cp) const {
-  const EpdUnicodeInterval* intervals = data->intervals;
-  const int count = data->intervalCount;
+static uint8_t lookupKernClass(const EpdKernClassEntry* entries, const uint16_t count, const uint32_t cp) {
+  if (!entries || count == 0 || cp > 0xFFFF) {
+    return 0;
+  }
 
+  const auto target = static_cast<uint16_t>(cp);
+  const auto* end = entries + count;
+
+  // lower_bound: exact-key lookup. Finds the first entry with codepoint >= target,
+  // then the equality check confirms an exact match exists.
+  const auto it = std::lower_bound(
+      entries, end, target, [](const EpdKernClassEntry& entry, uint16_t value) { return entry.codepoint < value; });
+
+  if (it != end && it->codepoint == target) {
+    return it->classId;
+  }
+
+  return 0;
+}
+
+int8_t EpdFont::getKerning(const uint32_t leftCp, const uint32_t rightCp) const {
+  if (!data->kernMatrix) {
+    return 0;
+  }
+  const uint8_t lc = lookupKernClass(data->kernLeftClasses, data->kernLeftEntryCount, leftCp);
+  if (lc == 0) return 0;
+  const uint8_t rc = lookupKernClass(data->kernRightClasses, data->kernRightEntryCount, rightCp);
+  if (rc == 0) return 0;
+  return data->kernMatrix[(lc - 1) * data->kernRightClassCount + (rc - 1)];
+}
+
+uint32_t EpdFont::getLigature(const uint32_t leftCp, const uint32_t rightCp) const {
+  const auto* pairs = data->ligaturePairs;
+  const auto count = data->ligaturePairCount;
+  if (!pairs || count == 0 || leftCp > 0xFFFF || rightCp > 0xFFFF) {
+    return 0;
+  }
+
+  const uint32_t key = (leftCp << 16) | rightCp;
+  const auto* end = pairs + count;
+
+  // lower_bound: exact-key lookup. Finds the first entry with pair >= key,
+  // then the equality check confirms an exact match exists.
+  const auto it =
+      std::lower_bound(pairs, end, key, [](const EpdLigaturePair& pair, uint32_t value) { return pair.pair < value; });
+
+  if (it != end && it->pair == key) {
+    return it->ligatureCp;
+  }
+
+  return 0;
+}
+
+uint32_t EpdFont::applyLigatures(uint32_t cp, const char*& text) const {
+  if (!data->ligaturePairs || data->ligaturePairCount == 0) {
+    return cp;
+  }
+  while (true) {
+    const auto saved = reinterpret_cast<const uint8_t*>(text);
+    const uint32_t nextCp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&text));
+    if (nextCp == 0) break;
+    const uint32_t lig = getLigature(cp, nextCp);
+    if (lig == 0) {
+      text = reinterpret_cast<const char*>(saved);
+      break;
+    }
+    cp = lig;
+  }
+  return cp;
+}
+
+const EpdGlyph* EpdFont::getGlyph(const uint32_t cp) const {
+  const int count = data->intervalCount;
   if (count == 0) return nullptr;
 
-  // Binary search for O(log n) lookup instead of O(n)
-  // Critical for Korean fonts with many unicode intervals
-  int left = 0;
-  int right = count - 1;
+  const EpdUnicodeInterval* intervals = data->intervals;
+  const auto* end = intervals + count;
 
-  while (left <= right) {
-    const int mid = left + (right - left) / 2;
-    const EpdUnicodeInterval* interval = &intervals[mid];
+  // upper_bound: range lookup. Finds the first interval with first > cp, so the
+  // interval just before it is the last one with first <= cp. That's the only
+  // candidate that could contain cp. Then we verify cp <= candidate.last.
+  const auto it = std::upper_bound(
+      intervals, end, cp, [](uint32_t value, const EpdUnicodeInterval& interval) { return value < interval.first; });
 
-    if (cp < interval->first) {
-      right = mid - 1;
-    } else if (cp > interval->last) {
-      left = mid + 1;
-    } else {
-      // Found: cp >= interval->first && cp <= interval->last
-      return &data->glyph[interval->offset + (cp - interval->first)];
+  if (it != intervals) {
+    const auto& interval = *(it - 1);
+    if (cp <= interval.last) {
+      return &data->glyph[interval.offset + (cp - interval.first)];
     }
   }
 
+  if (cp != REPLACEMENT_GLYPH) {
+    return getGlyph(REPLACEMENT_GLYPH);
+  }
   return nullptr;
 }

lib/EpdFont/EpdFont.h

@@ -11,4 +11,16 @@ class EpdFont {
   void getTextDimensions(const char* string, int* w, int* h) const;
 
   const EpdGlyph* getGlyph(uint32_t cp) const;
+
+  /// Returns the kerning adjustment (4.4 fixed-point in pixels) between two codepoints.
+  /// Returns 0 if no kerning data exists for the pair.
+  int8_t getKerning(uint32_t leftCp, uint32_t rightCp) const;
+
+  /// Returns the ligature codepoint for a pair, or 0 if no ligature exists.
+  uint32_t getLigature(uint32_t leftCp, uint32_t rightCp) const;
+
+  /// Greedily applies ligature substitutions starting from cp, consuming
+  /// as many following codepoints from text as possible. Returns the
+  /// (possibly substituted) codepoint; advances text past consumed chars.
+  uint32_t applyLigatures(uint32_t cp, const char*& text) const;
 };

lib/EpdFont/EpdFontData.h

@@ -4,11 +4,40 @@
 #pragma once
 #include <cstdint>
 
+/// Font metrics use "fixed-point 4" (4 fractional bits, i.e. 1/16-pixel
+/// resolution).  Both the 12.4 glyph advances (uint16_t) and the 4.4 kern
+/// values (int8_t) share the same 4 fractional bits, so they can be freely
+/// added into a single int32_t accumulator during text layout.  The
+/// accumulator is snapped to the nearest whole pixel only at render time,
+/// which avoids the per-character rounding errors that plagued integer-only
+/// layout.
+///
+/// The helpers below eliminate the raw bit-shifts that would otherwise be
+/// scattered across every layout / measurement call site.
+namespace fp4 {
+constexpr int FRAC_BITS = 4;
+constexpr int32_t HALF = 1 << (FRAC_BITS - 1);  // 8, added before shift for round-to-nearest
+
+/// Convert an integer pixel value to 12.4 fixed-point.
+constexpr int32_t fromPixel(int px) { return static_cast<int32_t>(px) << FRAC_BITS; }
+
+/// Snap a fixed-point value to the nearest integer pixel.
+constexpr int toPixel(int32_t fp) { return static_cast<int>((fp + HALF) >> FRAC_BITS); }
+
+/// Convert a fixed-point value to float (mainly useful for debug logging).
+constexpr float toFloat(int32_t fp) { return fp / static_cast<float>(1 << FRAC_BITS); }
+}  // namespace fp4
+
+/// Fixed-point conventions used by EpdGlyph and EpdFontData:
+///   advanceX:   12.4 unsigned fixed-point in uint16_t  (use fp4::toPixel)
+///   kernMatrix:  4.4 signed fixed-point in int8_t      (use fp4::toPixel)
+/// Both share 4 fractional bits so they combine directly in an accumulator.
+
 /// Font data stored PER GLYPH
 typedef struct {
   uint8_t width;        ///< Bitmap dimensions in pixels
   uint8_t height;       ///< Bitmap dimensions in pixels
-  uint8_t advanceX;     ///< Distance to advance cursor (x axis)
+  uint16_t advanceX;    ///< Distance to advance cursor (x axis), 12.4 fixed-point in pixels
   int16_t left;         ///< X dist from cursor pos to UL corner
   int16_t top;          ///< Y dist from cursor pos to UL corner
   uint16_t dataLength;  ///< Size of the font data.
@@ -21,7 +50,7 @@ typedef struct {
   uint32_t compressedSize;    ///< Compressed DEFLATE stream size
   uint32_t uncompressedSize;  ///< Decompressed size
   uint16_t glyphCount;        ///< Number of glyphs in this group
-  uint16_t firstGlyphIndex;   ///< First glyph index in the global glyph array
+  uint32_t firstGlyphIndex;   ///< First glyph index in the global glyph array
 } EpdFontGroup;
 
 /// Glyph interval structure
@@ -31,6 +60,20 @@ typedef struct {
   uint32_t offset;  ///< Index of the first code point into the glyph array
 } EpdUnicodeInterval;
 
+/// Maps a codepoint to a kerning class ID, sorted by codepoint for binary search.
+/// Class IDs are 1-based; codepoints not in the table have implicit class 0 (no kerning).
+typedef struct {
+  uint16_t codepoint;  ///< Unicode codepoint
+  uint8_t classId;     ///< 1-based kerning class ID
+} __attribute__((packed)) EpdKernClassEntry;
+
+/// Ligature substitution for a specific glyph pair, sorted by `pair` for binary search.
+/// `pair` encodes (leftCodepoint << 16 | rightCodepoint) for single-key lookup.
+typedef struct {
+  uint32_t pair;        ///< Packed codepoint pair (left << 16 | right)
+  uint32_t ligatureCp;  ///< Codepoint of the replacement ligature glyph
+} __attribute__((packed)) EpdLigaturePair;
+
 /// Data stored for FONT AS A WHOLE
 typedef struct {
   const uint8_t* bitmap;                ///< Glyph bitmaps, concatenated
@@ -41,6 +84,16 @@ typedef struct {
   int ascender;                         ///< Maximal height of a glyph above the base line
   int descender;                        ///< Maximal height of a glyph below the base line
   bool is2Bit;
-  const EpdFontGroup* groups;  ///< NULL for uncompressed fonts
-  uint16_t groupCount;         ///< 0 for uncompressed fonts
+  const EpdFontGroup* groups;                 ///< NULL for uncompressed fonts
+  uint16_t groupCount;                        ///< 0 for uncompressed fonts
+  const uint16_t* glyphToGroup;               ///< Per-glyph group ID (nullptr for contiguous-group fonts)
+  const EpdKernClassEntry* kernLeftClasses;   ///< Sorted left-side class map (nullptr if none)
+  const EpdKernClassEntry* kernRightClasses;  ///< Sorted right-side class map (nullptr if none)
+  const int8_t* kernMatrix;              ///< Flat leftClassCount x rightClassCount matrix, 4.4 fixed-point in pixels
+  uint16_t kernLeftEntryCount;           ///< Entries in kernLeftClasses
+  uint16_t kernRightEntryCount;          ///< Entries in kernRightClasses
+  uint8_t kernLeftClassCount;            ///< Number of distinct left classes (matrix rows)
+  uint8_t kernRightClassCount;           ///< Number of distinct right classes (matrix cols)
+  const EpdLigaturePair* ligaturePairs;  ///< Sorted ligature pair table (nullptr if none)
+  uint32_t ligaturePairCount;            ///< Number of entries in ligaturePairs
 } EpdFontData;

lib/EpdFont/EpdFontFamily.cpp

@@ -26,4 +26,12 @@ const EpdFontData* EpdFontFamily::getData(const Style style) const { return getF
 
 const EpdGlyph* EpdFontFamily::getGlyph(const uint32_t cp, const Style style) const {
   return getFont(style)->getGlyph(cp);
-};
+}
+
+int8_t EpdFontFamily::getKerning(const uint32_t leftCp, const uint32_t rightCp, const Style style) const {
+  return getFont(style)->getKerning(leftCp, rightCp);
+}
+
+uint32_t EpdFontFamily::applyLigatures(const uint32_t cp, const char*& text, const Style style) const {
+  return getFont(style)->applyLigatures(cp, text);
+}

lib/EpdFont/EpdFontFamily.h

@@ -12,6 +12,8 @@ class EpdFontFamily {
   void getTextDimensions(const char* string, int* w, int* h, Style style = REGULAR) const;
   const EpdFontData* getData(Style style = REGULAR) const;
   const EpdGlyph* getGlyph(uint32_t cp, Style style = REGULAR) const;
+  int8_t getKerning(uint32_t leftCp, uint32_t rightCp, Style style = REGULAR) const;
+  uint32_t applyLigatures(uint32_t cp, const char*& text, Style style = REGULAR) const;
 
  private:
   const EpdFont* regular;

lib/EpdFont/FontDecompressor.cpp

@@ -1,37 +1,55 @@
 #include "FontDecompressor.h"
 
+#include <Arduino.h>
 #include <Logging.h>
-#include <uzlib.h>
+#include <Utf8.h>
 
 #include <cstdlib>
-#include <cstring>
+
+FontDecompressor::~FontDecompressor() { deinit(); }
 
 bool FontDecompressor::init() {
   clearCache();
-  memset(&decomp, 0, sizeof(decomp));
   return true;
 }
 
-void FontDecompressor::freeAllEntries() {
-  for (auto& entry : cache) {
-    if (entry.data) {
-      free(entry.data);
-      entry.data = nullptr;
-    }
-    entry.valid = false;
-  }
+void FontDecompressor::deinit() {
+  freePageBuffer();
+  freeHotGroup();
 }
 
-void FontDecompressor::deinit() { freeAllEntries(); }
-
 void FontDecompressor::clearCache() {
-  freeAllEntries();
-  accessCounter = 0;
+  freePageBuffer();
+  freeHotGroup();
 }
 
-uint16_t FontDecompressor::getGroupIndex(const EpdFontData* fontData, uint16_t glyphIndex) {
+void FontDecompressor::freePageBuffer() {
+  for (uint8_t s = 0; s < pageSlotCount; s++) {
+    free(pageSlots[s].buffer);
+    free(pageSlots[s].glyphs);
+    pageSlots[s] = {};
+  }
+  pageSlotCount = 0;
+}
+
+void FontDecompressor::freeHotGroup() {
+  hotGroup.clear();
+  hotGroup.shrink_to_fit();
+  hotGroupFont = nullptr;
+  hotGroupIndex = UINT16_MAX;
+  hotGlyphBuf.clear();
+  hotGlyphBuf.shrink_to_fit();
+}
+
+uint16_t FontDecompressor::getGroupIndex(const EpdFontData* fontData, uint32_t glyphIndex) {
+  // O(1) path for frequency-grouped fonts with glyphToGroup mapping
+  if (fontData->glyphToGroup != nullptr) {
+    return fontData->glyphToGroup[glyphIndex];
+  }
+
+  // Contiguous-group fonts: linear scan
   for (uint16_t i = 0; i < fontData->groupCount; i++) {
-    uint16_t first = fontData->groups[i].firstGlyphIndex;
+    uint32_t first = fontData->groups[i].firstGlyphIndex;
     if (glyphIndex >= first && glyphIndex < first + fontData->groups[i].glyphCount) {
       return i;
     }
@@ -39,109 +57,425 @@ uint16_t FontDecompressor::getGroupIndex(const EpdFontData* fontData, uint16_t g
   return fontData->groupCount;  // sentinel = not found
 }
 
-FontDecompressor::CacheEntry* FontDecompressor::findInCache(const EpdFontData* fontData, uint16_t groupIndex) {
-  for (auto& entry : cache) {
-    if (entry.valid && entry.font == fontData && entry.groupIndex == groupIndex) {
-      return &entry;
-    }
-  }
-  return nullptr;
-}
-
-FontDecompressor::CacheEntry* FontDecompressor::findEvictionCandidate() {
-  // Find an invalid slot first
-  for (auto& entry : cache) {
-    if (!entry.valid) {
-      return &entry;
-    }
-  }
-  // Otherwise evict LRU
-  CacheEntry* lru = &cache[0];
-  for (auto& entry : cache) {
-    if (entry.lastUsed < lru->lastUsed) {
-      lru = &entry;
-    }
-  }
-  return lru;
-}
-
-bool FontDecompressor::decompressGroup(const EpdFontData* fontData, uint16_t groupIndex, CacheEntry* entry) {
+bool FontDecompressor::decompressGroup(const EpdFontData* fontData, uint16_t groupIndex, uint8_t* outBuf,
+                                       uint32_t outSize) {
   const EpdFontGroup& group = fontData->groups[groupIndex];
 
-  // Free old buffer if reusing a slot
-  if (entry->data) {
-    free(entry->data);
-    entry->data = nullptr;
-  }
-  entry->valid = false;
-
-  // Allocate output buffer
-  auto* outBuf = static_cast<uint8_t*>(malloc(group.uncompressedSize));
-  if (!outBuf) {
-    LOG_ERR("FDC", "Failed to allocate %u bytes for group %u", group.uncompressedSize, groupIndex);
+  const uint32_t tDecomp = millis();
+  inflateReader.init(false);
+  inflateReader.setSource(&fontData->bitmap[group.compressedOffset], group.compressedSize);
+  if (!inflateReader.read(outBuf, outSize)) {
+    stats.decompressTimeMs += millis() - tDecomp;
+    LOG_ERR("FDC", "Decompression failed for group %u", groupIndex);
     return false;
   }
-
-  // Decompress using uzlib
-  const uint8_t* inputBuf = &fontData->bitmap[group.compressedOffset];
-
-  uzlib_uncompress_init(&decomp, NULL, 0);
-  decomp.source = inputBuf;
-  decomp.source_limit = inputBuf + group.compressedSize;
-  decomp.dest_start = outBuf;
-  decomp.dest = outBuf;
-  decomp.dest_limit = outBuf + group.uncompressedSize;
-
-  int res = uzlib_uncompress(&decomp);
-
-  if (res < 0 || decomp.dest != decomp.dest_limit) {
-    LOG_ERR("FDC", "Decompression failed for group %u (status %d)", groupIndex, res);
-    free(outBuf);
-    return false;
-  }
-
-  entry->font = fontData;
-  entry->groupIndex = groupIndex;
-  entry->data = outBuf;
-  entry->dataSize = group.uncompressedSize;
-  entry->valid = true;
+  stats.decompressTimeMs += millis() - tDecomp;
   return true;
 }
 
-const uint8_t* FontDecompressor::getBitmap(const EpdFontData* fontData, const EpdGlyph* glyph, uint16_t glyphIndex) {
+// --- Byte-aligned helpers ---
+
+uint32_t FontDecompressor::getAlignedOffset(const EpdFontData* fontData, uint16_t groupIndex, uint32_t glyphIndex) {
+  uint32_t offset = 0;
+
+  auto accumGlyph = [&](const EpdGlyph& g) {
+    if (g.width > 0 && g.height > 0) {
+      offset += ((g.width + 3) / 4) * g.height;
+    }
+  };
+
+  if (fontData->glyphToGroup) {
+    // Frequency-grouped: scan glyphs before glyphIndex that belong to this group
+    for (uint32_t i = 0; i < glyphIndex; i++) {
+      if (fontData->glyphToGroup[i] == groupIndex) {
+        accumGlyph(fontData->glyph[i]);
+      }
+    }
+  } else {
+    // Contiguous-group: sum aligned sizes of preceding glyphs in the group
+    const EpdFontGroup& group = fontData->groups[groupIndex];
+    for (uint32_t i = group.firstGlyphIndex; i < glyphIndex; i++) {
+      accumGlyph(fontData->glyph[i]);
+    }
+  }
+
+  return offset;
+}
+
+void FontDecompressor::compactSingleGlyph(const uint8_t* alignedSrc, uint8_t* packedDst, uint8_t width,
+                                          uint8_t height) {
+  if (width == 0 || height == 0) return;
+  const uint32_t rowStride = (width + 3) / 4;
+  if (width % 4 == 0) {
+    memcpy(packedDst, alignedSrc, rowStride * height);
+    return;
+  }
+  uint8_t outByte = 0, outBits = 0;
+  uint32_t writeIdx = 0;
+  for (uint8_t y = 0; y < height; y++) {
+    for (uint8_t x = 0; x < width; x++) {
+      outByte = (outByte << 2) | ((alignedSrc[y * rowStride + x / 4] >> ((3 - (x % 4)) * 2)) & 0x3);
+      outBits += 2;
+      if (outBits == 8) {
+        packedDst[writeIdx++] = outByte;
+        outByte = 0;
+        outBits = 0;
+      }
+    }
+  }
+  if (outBits > 0) packedDst[writeIdx] = outByte << (8 - outBits);
+}
+
+// --- getBitmap: page buffer → hot group → decompress ---
+
+const uint8_t* FontDecompressor::getBitmap(const EpdFontData* fontData, const EpdGlyph* glyph, uint32_t glyphIndex) {
+  const uint32_t tStart = micros();
+  stats.getBitmapCalls++;
+
   if (!fontData->groups || fontData->groupCount == 0) {
+    stats.getBitmapTimeUs += micros() - tStart;
     return &fontData->bitmap[glyph->dataOffset];
   }
 
+  // Check page buffer slots (populated by prewarmCache — one slot per font style)
+  for (uint8_t s = 0; s < pageSlotCount; s++) {
+    const auto& slot = pageSlots[s];
+    if (slot.fontData != fontData || slot.glyphCount == 0) continue;
+
+    int left = 0, right = slot.glyphCount - 1;
+    while (left <= right) {
+      int mid = left + (right - left) / 2;
+      if (slot.glyphs[mid].glyphIndex == glyphIndex) {
+        if (slot.glyphs[mid].bufferOffset != UINT32_MAX) {
+          stats.cacheHits++;
+          stats.getBitmapTimeUs += micros() - tStart;
+          return &slot.buffer[slot.glyphs[mid].bufferOffset];
+        }
+        break;  // Not extracted during prewarm; fall through to hot-group path
+      }
+      if (slot.glyphs[mid].glyphIndex < glyphIndex)
+        left = mid + 1;
+      else
+        right = mid - 1;
+    }
+    break;  // Found the right slot but glyph wasn't in it; don't check other slots
+  }
+
+  // Fallback: hot group slot
   uint16_t groupIndex = getGroupIndex(fontData, glyphIndex);
   if (groupIndex >= fontData->groupCount) {
     LOG_ERR("FDC", "Glyph %u not found in any group", glyphIndex);
+    stats.getBitmapTimeUs += micros() - tStart;
     return nullptr;
   }
 
-  // Check cache
-  CacheEntry* entry = findInCache(fontData, groupIndex);
-  if (entry) {
-    entry->lastUsed = ++accessCounter;
-    if (glyph->dataOffset + glyph->dataLength > entry->dataSize) {
-      LOG_ERR("FDC", "dataOffset %u + dataLength %u out of bounds for group %u (size %u)", glyph->dataOffset,
-              glyph->dataLength, groupIndex, entry->dataSize);
+  // Check if hot group already has this group decompressed — if not, decompress it
+  if (!(!hotGroup.empty() && hotGroupFont == fontData && hotGroupIndex == groupIndex)) {
+    stats.cacheMisses++;
+    const EpdFontGroup& group = fontData->groups[groupIndex];
+
+    hotGroup.resize(group.uncompressedSize);
+    if (hotGroup.empty()) {
+      LOG_ERR("FDC", "Failed to allocate %u bytes for hot group %u", group.uncompressedSize, groupIndex);
+      hotGroupFont = nullptr;
+      hotGroupIndex = UINT16_MAX;
+      stats.getBitmapTimeUs += micros() - tStart;
       return nullptr;
     }
-    return &entry->data[glyph->dataOffset];
+
+    if (!decompressGroup(fontData, groupIndex, hotGroup.data(), group.uncompressedSize)) {
+      hotGroup.clear();
+      hotGroup.shrink_to_fit();
+      hotGroupFont = nullptr;
+      hotGroupIndex = UINT16_MAX;
+      stats.getBitmapTimeUs += micros() - tStart;
+      return nullptr;
+    }
+
+    hotGroupFont = fontData;
+    hotGroupIndex = groupIndex;
+    stats.hotGroupBytes = group.uncompressedSize;
+  } else {
+    stats.cacheHits++;
   }
 
-  // Cache miss - decompress
-  entry = findEvictionCandidate();
-  if (!decompressGroup(fontData, groupIndex, entry)) {
+  // Compact just the requested glyph from byte-aligned data into scratch buffer
+  if (glyph->dataLength > hotGlyphBuf.size()) {
+    hotGlyphBuf.resize(glyph->dataLength);
+  }
+  if (hotGlyphBuf.empty()) {
+    stats.getBitmapTimeUs += micros() - tStart;
     return nullptr;
   }
 
-  entry->lastUsed = ++accessCounter;
-  if (glyph->dataOffset + glyph->dataLength > entry->dataSize) {
-    LOG_ERR("FDC", "dataOffset %u + dataLength %u out of bounds for group %u (size %u)", glyph->dataOffset,
-            glyph->dataLength, groupIndex, entry->dataSize);
-    return nullptr;
+  uint32_t alignedOff = getAlignedOffset(fontData, groupIndex, glyphIndex);
+  compactSingleGlyph(&hotGroup[alignedOff], hotGlyphBuf.data(), glyph->width, glyph->height);
+  stats.getBitmapTimeUs += micros() - tStart;
+  return hotGlyphBuf.data();
+}
+
+// --- Prewarm: pre-decompress glyph bitmaps for a page of text ---
+
+int32_t FontDecompressor::findGlyphIndex(const EpdFontData* fontData, uint32_t codepoint) {
+  const EpdUnicodeInterval* intervals = fontData->intervals;
+  const int count = fontData->intervalCount;
+
+  if (count == 0) return -1;
+
+  // Binary search
+  int left = 0;
+  int right = count - 1;
+
+  while (left <= right) {
+    const int mid = left + (right - left) / 2;
+    const EpdUnicodeInterval* interval = &intervals[mid];
+
+    if (codepoint < interval->first) {
+      right = mid - 1;
+    } else if (codepoint > interval->last) {
+      left = mid + 1;
+    } else {
+      return static_cast<int32_t>(interval->offset + (codepoint - interval->first));
+    }
   }
-  return &entry->data[glyph->dataOffset];
+
+  return -1;
+}
+
+int FontDecompressor::prewarmCache(const EpdFontData* fontData, const char* utf8Text) {
+  if (!fontData || !fontData->groups || !utf8Text) return 0;
+
+  // Allocate the next available slot (caller must call freePageBuffer/clearCache to reset)
+  if (pageSlotCount >= MAX_PAGE_SLOTS) {
+    LOG_ERR("FDC", "All %u page buffer slots full, cannot prewarm fontData=%p", MAX_PAGE_SLOTS, (void*)fontData);
+    return -1;
+  }
+  PageSlot& slot = pageSlots[pageSlotCount];
+
+  // Step 1: Collect unique glyph indices needed for this page
+  uint32_t neededGlyphs[MAX_PAGE_GLYPHS];
+  uint16_t glyphCount = 0;
+  bool glyphCapWarned = false;
+
+  const unsigned char* p = reinterpret_cast<const unsigned char*>(utf8Text);
+  while (*p) {
+    uint32_t cp = utf8NextCodepoint(&p);
+    if (cp == 0) break;
+
+    int32_t glyphIdx = findGlyphIndex(fontData, cp);
+    if (glyphIdx < 0) continue;
+
+    // Deduplicate
+    bool found = false;
+    for (uint16_t i = 0; i < glyphCount; i++) {
+      if (neededGlyphs[i] == static_cast<uint32_t>(glyphIdx)) {
+        found = true;
+        break;
+      }
+    }
+    if (!found) {
+      if (glyphCount < MAX_PAGE_GLYPHS) {
+        neededGlyphs[glyphCount++] = static_cast<uint32_t>(glyphIdx);
+      } else if (!glyphCapWarned) {
+        LOG_DBG("FDC", "Glyph cap (%u) reached during prewarm; excess glyphs will use hot-group fallback",
+                MAX_PAGE_GLYPHS);
+        glyphCapWarned = true;
+      }
+    }
+  }
+
+  if (glyphCount == 0) return 0;
+
+  // Step 2: Compute total buffer size and collect unique groups
+  uint32_t totalBytes = 0;
+  uint16_t neededGroups[128];
+  uint8_t groupCount = 0;
+  bool groupCapWarned = false;
+
+  for (uint16_t i = 0; i < glyphCount; i++) {
+    totalBytes += fontData->glyph[neededGlyphs[i]].dataLength;
+    uint16_t gi = getGroupIndex(fontData, neededGlyphs[i]);
+    bool found = false;
+    for (uint8_t j = 0; j < groupCount; j++) {
+      if (neededGroups[j] == gi) {
+        found = true;
+        break;
+      }
+    }
+    if (!found) {
+      if (groupCount < 128) {
+        neededGroups[groupCount++] = gi;
+      } else if (!groupCapWarned) {
+        LOG_DBG("FDC", "Group cap (128) reached during prewarm; some groups will use hot-group fallback");
+        groupCapWarned = true;
+      }
+    }
+  }
+
+  stats.uniqueGroupsAccessed = groupCount;
+
+  // Step 3: Allocate page buffer and lookup table for this slot
+  slot.buffer = static_cast<uint8_t*>(malloc(totalBytes));
+  slot.glyphs = static_cast<PageGlyphEntry*>(malloc(glyphCount * sizeof(PageGlyphEntry)));
+  if (!slot.buffer || !slot.glyphs) {
+    LOG_ERR("FDC", "Failed to allocate page buffer (%u bytes, %u glyphs)", totalBytes, glyphCount);
+    free(slot.buffer);
+    free(slot.glyphs);
+    slot = {};
+    return glyphCount;
+  }
+  stats.pageBufferBytes += totalBytes;
+  stats.pageGlyphsBytes += glyphCount * sizeof(PageGlyphEntry);
+
+  slot.fontData = fontData;
+  slot.glyphCount = glyphCount;
+  pageSlotCount++;
+
+  // Initialize lookup entries (bufferOffset = UINT32_MAX means not yet extracted)
+  for (uint16_t i = 0; i < glyphCount; i++) {
+    slot.glyphs[i] = {neededGlyphs[i], UINT32_MAX, 0};
+  }
+
+  // Sort by glyphIndex for binary search in getBitmap()
+  for (uint16_t i = 1; i < glyphCount; i++) {
+    PageGlyphEntry key = slot.glyphs[i];
+    int j = i - 1;
+    while (j >= 0 && slot.glyphs[j].glyphIndex > key.glyphIndex) {
+      slot.glyphs[j + 1] = slot.glyphs[j];
+      j--;
+    }
+    slot.glyphs[j + 1] = key;
+  }
+
+  // Step 3b: Pre-scan to compute each needed glyph's byte-aligned offset within its group.
+  // This avoids recomputing aligned offsets per group during extraction in step 4.
+  uint32_t groupAlignedTracker[128] = {};  // running byte-aligned offset for each needed group
+
+  if (fontData->glyphToGroup) {
+    // Frequency-grouped: single O(totalGlyphs) pass through glyphToGroup
+    const auto& lastInterval = fontData->intervals[fontData->intervalCount - 1];
+    const uint32_t totalGlyphs = lastInterval.offset + (lastInterval.last - lastInterval.first + 1);
+
+    for (uint32_t i = 0; i < totalGlyphs; i++) {
+      const uint16_t gi = fontData->glyphToGroup[i];
+      // Find this glyph's group position in neededGroups
+      uint8_t gpPos = groupCount;
+      for (uint8_t j = 0; j < groupCount; j++) {
+        if (neededGroups[j] == gi) {
+          gpPos = j;
+          break;
+        }
+      }
+      if (gpPos == groupCount) continue;  // not a needed group
+
+      const EpdGlyph& glyph = fontData->glyph[i];
+
+      // Binary search in sorted slot.glyphs to find if glyph i is needed
+      int left = 0, right = (int)slot.glyphCount - 1;
+      while (left <= right) {
+        const int mid = left + (right - left) / 2;
+        if (slot.glyphs[mid].glyphIndex == i) {
+          slot.glyphs[mid].alignedOffset = groupAlignedTracker[gpPos];
+          break;
+        }
+        if (slot.glyphs[mid].glyphIndex < i)
+          left = mid + 1;
+        else
+          right = mid - 1;
+      }
+
+      if (glyph.width > 0 && glyph.height > 0) {
+        groupAlignedTracker[gpPos] += ((glyph.width + 3) / 4) * glyph.height;
+      }
+    }
+  } else {
+    // Contiguous-group: iterate each needed group's glyphs directly
+    for (uint8_t g = 0; g < groupCount; g++) {
+      const EpdFontGroup& group = fontData->groups[neededGroups[g]];
+      uint32_t alignedOff = 0;
+      for (uint16_t j = 0; j < group.glyphCount; j++) {
+        const uint32_t glyphI = group.firstGlyphIndex + j;
+        const EpdGlyph& glyph = fontData->glyph[glyphI];
+
+        int left = 0, right = (int)slot.glyphCount - 1;
+        while (left <= right) {
+          const int mid = left + (right - left) / 2;
+          if (slot.glyphs[mid].glyphIndex == glyphI) {
+            slot.glyphs[mid].alignedOffset = alignedOff;
+            break;
+          }
+          if (slot.glyphs[mid].glyphIndex < glyphI)
+            left = mid + 1;
+          else
+            right = mid - 1;
+        }
+
+        if (glyph.width > 0 && glyph.height > 0) {
+          alignedOff += ((glyph.width + 3) / 4) * glyph.height;
+        }
+      }
+    }
+  }
+
+  // Step 4: For each unique group, decompress to temp buffer and extract needed glyphs
+  uint32_t writeOffset = 0;
+  int missed = 0;
+
+  for (uint8_t g = 0; g < groupCount; g++) {
+    uint16_t groupIdx = neededGroups[g];
+    const EpdFontGroup& group = fontData->groups[groupIdx];
+
+    auto* tempBuf = static_cast<uint8_t*>(malloc(group.uncompressedSize));
+    if (!tempBuf) {
+      LOG_ERR("FDC", "Failed to allocate temp buffer (%u bytes) for group %u", group.uncompressedSize, groupIdx);
+      missed++;
+      continue;
+    }
+    if (group.uncompressedSize > stats.peakTempBytes) {
+      stats.peakTempBytes = group.uncompressedSize;
+    }
+
+    if (!decompressGroup(fontData, groupIdx, tempBuf, group.uncompressedSize)) {
+      free(tempBuf);
+      missed++;
+      continue;
+    }
+
+    // Extract needed glyphs directly from the byte-aligned temp buffer, compacting on the fly.
+    // alignedOffset was pre-computed in step 3b — no full-group compact scan needed.
+    for (uint16_t i = 0; i < slot.glyphCount; i++) {
+      if (slot.glyphs[i].bufferOffset != UINT32_MAX) continue;  // already extracted
+      if (getGroupIndex(fontData, slot.glyphs[i].glyphIndex) != groupIdx) continue;
+
+      const EpdGlyph& glyph = fontData->glyph[slot.glyphs[i].glyphIndex];
+      compactSingleGlyph(&tempBuf[slot.glyphs[i].alignedOffset], &slot.buffer[writeOffset], glyph.width, glyph.height);
+      slot.glyphs[i].bufferOffset = writeOffset;
+      writeOffset += glyph.dataLength;
+    }
+
+    free(tempBuf);
+  }
+
+  LOG_DBG("FDC", "Prewarm: %u glyphs in %u bytes from %u groups (%d missed)", glyphCount, writeOffset, groupCount,
+          missed);
+
+  return missed;
+}
+
+// --- Stats ---
+
+void FontDecompressor::resetStats() { stats = Stats{}; }
+
+void FontDecompressor::logStats(const char* label) {
+  const uint32_t total = stats.cacheHits + stats.cacheMisses;
+  LOG_DBG("FDC", "[%s] hits=%lu misses=%lu (%.1f%% hit rate)", label, stats.cacheHits, stats.cacheMisses,
+          total > 0 ? 100.0f * stats.cacheHits / total : 0.0f);
+  LOG_DBG("FDC", "[%s] decompress=%lums groups_accessed=%u", label, stats.decompressTimeMs, stats.uniqueGroupsAccessed);
+  LOG_DBG("FDC", "[%s] mem: pageBuf=%lu pageGlyphs=%lu hotGroup=%lu peakTemp=%lu", label, stats.pageBufferBytes,
+          stats.pageGlyphsBytes, stats.hotGroupBytes, stats.peakTempBytes);
+  if (stats.getBitmapCalls > 0) {
+    LOG_DBG("FDC", "[%s] getBitmap: %lu calls, %luus total, %luus/call avg", label, stats.getBitmapCalls,
+            stats.getBitmapTimeUs, stats.getBitmapTimeUs / stats.getBitmapCalls);
+  }
+  resetStats();
 }

lib/EpdFont/FontDecompressor.h

@@ -1,42 +1,85 @@
 #pragma once
 
-#include <uzlib.h>
+#include <InflateReader.h>
 
-#include <cstdint>
+#include <vector>
 
 #include "EpdFontData.h"
 
 class FontDecompressor {
  public:
+  static constexpr uint16_t MAX_PAGE_GLYPHS = 512;
+  static constexpr uint8_t MAX_PAGE_SLOTS = 4;  // One per font style (R/B/I/BI)
+
+  FontDecompressor() = default;
+  ~FontDecompressor();
+
   bool init();
   void deinit();
 
   // Returns pointer to decompressed bitmap data for the given glyph.
-  // Valid until LRU eviction (safe for the duration of one glyph render).
-  const uint8_t* getBitmap(const EpdFontData* fontData, const EpdGlyph* glyph, uint16_t glyphIndex);
+  // Checks the page buffer (from prewarm) first, then falls back to the hot group slot.
+  const uint8_t* getBitmap(const EpdFontData* fontData, const EpdGlyph* glyph, uint32_t glyphIndex);
 
-  // Evict all cached decompressed groups (call between pages for within-page-only caching).
+  // Free all cached data (page buffer + hot group).
   void clearCache();
 
- private:
-  static constexpr uint8_t CACHE_SLOTS = 4;
+  // Pre-scan UTF-8 text and extract needed glyph bitmaps into a flat page buffer.
+  // Each group is decompressed once into a temp buffer; only needed glyphs are kept.
+  // Returns the number of glyphs that couldn't be loaded (0 on full success).
+  int prewarmCache(const EpdFontData* fontData, const char* utf8Text);
 
-  struct CacheEntry {
-    const EpdFontData* font = nullptr;
-    uint16_t groupIndex = 0;
-    uint8_t* data = nullptr;
-    uint32_t dataSize = 0;
-    uint32_t lastUsed = 0;
-    bool valid = false;
+  struct Stats {
+    uint32_t cacheHits = 0;
+    uint32_t cacheMisses = 0;
+    uint32_t decompressTimeMs = 0;
+    uint16_t uniqueGroupsAccessed = 0;
+    uint32_t pageBufferBytes = 0;  // pageBuffer allocation
+    uint32_t pageGlyphsBytes = 0;  // pageGlyphs lookup table allocation
+    uint32_t hotGroupBytes = 0;    // current hot group allocation
+    uint32_t peakTempBytes = 0;    // largest temp buffer in prewarm
+    uint32_t getBitmapTimeUs = 0;  // cumulative getBitmap time (micros)
+    uint32_t getBitmapCalls = 0;   // number of getBitmap calls
   };
+  void logStats(const char* label = "FDC");
+  void resetStats();
+  const Stats& getStats() const { return stats; }
 
-  struct uzlib_uncomp decomp = {};
-  CacheEntry cache[CACHE_SLOTS] = {};
-  uint32_t accessCounter = 0;
+ private:
+  Stats stats;
+  InflateReader inflateReader;
 
-  void freeAllEntries();
-  uint16_t getGroupIndex(const EpdFontData* fontData, uint16_t glyphIndex);
-  CacheEntry* findInCache(const EpdFontData* fontData, uint16_t groupIndex);
-  CacheEntry* findEvictionCandidate();
-  bool decompressGroup(const EpdFontData* fontData, uint16_t groupIndex, CacheEntry* entry);
+  // Page buffer slots: each style gets its own flat glyph buffer with sorted lookup.
+  // Up to MAX_PAGE_SLOTS (4) styles can be prewarmed simultaneously.
+  struct PageGlyphEntry {
+    uint32_t glyphIndex;
+    uint32_t bufferOffset;
+    uint32_t alignedOffset;  // byte-aligned offset within its decompressed group (set during prewarm pre-scan)
+  };
+  struct PageSlot {
+    uint8_t* buffer = nullptr;
+    const EpdFontData* fontData = nullptr;
+    PageGlyphEntry* glyphs = nullptr;
+    uint16_t glyphCount = 0;
+  };
+  PageSlot pageSlots[MAX_PAGE_SLOTS] = {};
+  uint8_t pageSlotCount = 0;
+
+  // Hot group: last decompressed group (byte-aligned) for non-prewarmed fallback path.
+  // Kept in byte-aligned format; individual glyphs are compacted on demand into hotGlyphBuf.
+  const EpdFontData* hotGroupFont = nullptr;
+  uint16_t hotGroupIndex = UINT16_MAX;
+  std::vector<uint8_t> hotGroup;
+
+  // Scratch buffer for compacting a single glyph from the hot group.
+  // Valid until the next getBitmap() call.
+  std::vector<uint8_t> hotGlyphBuf;
+
+  void freePageBuffer();
+  void freeHotGroup();
+  uint16_t getGroupIndex(const EpdFontData* fontData, uint32_t glyphIndex);
+  uint32_t getAlignedOffset(const EpdFontData* fontData, uint16_t groupIndex, uint32_t glyphIndex);
+  bool decompressGroup(const EpdFontData* fontData, uint16_t groupIndex, uint8_t* outBuf, uint32_t outSize);
+  static void compactSingleGlyph(const uint8_t* alignedSrc, uint8_t* packedDst, uint8_t width, uint8_t height);
+  static int32_t findGlyphIndex(const EpdFontData* fontData, uint32_t codepoint);
 };

lib/EpdFont/scripts/fontconvert.py

@@ -6,6 +6,7 @@ import re
 import math
 import argparse
 from collections import namedtuple
+from fontTools.ttLib import TTFont
 
 # Originally from https://github.com/vroland/epdiy
 
@@ -16,6 +17,7 @@ parser.add_argument("fontstack", action="store", nargs='+', help="list of font f
 parser.add_argument("--2bit", dest="is2Bit", action="store_true", help="generate 2-bit greyscale bitmap instead of 1-bit black and white.")
 parser.add_argument("--additional-intervals", dest="additional_intervals", action="append", help="Additional code point intervals to export as min,max. This argument can be repeated.")
 parser.add_argument("--compress", dest="compress", action="store_true", help="Compress glyph bitmaps using DEFLATE with group-based compression.")
+parser.add_argument("--force-autohint", dest="force_autohint", action="store_true", help="Force FreeType auto-hinter instead of native font hinting. Improves stem width consistency for fonts with weak or no native TrueType hints.")
 args = parser.parse_args()
 
 GlyphProps = namedtuple("GlyphProps", ["width", "height", "advance_x", "left", "top", "data_length", "data_offset", "code_point"])
@@ -24,6 +26,9 @@ font_stack = [freetype.Face(f) for f in args.fontstack]
 is2Bit = args.is2Bit
 size = args.size
 font_name = args.name
+load_flags = freetype.FT_LOAD_RENDER
+if args.force_autohint:
+    load_flags |= freetype.FT_LOAD_FORCE_AUTOHINT
 
 # inclusive unicode code point intervals
 # must not overlap and be in ascending order
@@ -37,6 +42,18 @@ intervals = [
     ### Latin Extended-A ###
     # Eastern European and Baltic languages
     (0x0100, 0x017F),
+    ### Latin Extended-B (Vietnamese subset only) ###
+    # Only Ơ/ơ (U+01A0-01A1), Ư/ư (U+01AF-01B0) for Vietnamese
+    (0x01A0, 0x01A1),
+    (0x01AF, 0x01B0),
+    ### Latin Extended-B (European subset only) ###
+    # Croatian digraphs (DŽ/Lj/Nj), Pinyin caron variants,
+    # European diacritical variants, Romanian (Ș/ș/Ț/ț)
+    (0x01C4, 0x021F),
+    ### Vietnamese Extended ###
+    # All precomposed Vietnamese characters with tone marks
+    # Ả Ấ Ầ Ẩ Ẫ Ậ Ắ Ằ Ẳ Ẵ Ặ Ẹ Ẻ Ẽ Ế Ề Ể Ễ Ệ Ỉ Ị Ọ Ỏ Ố Ồ Ổ Ỗ Ộ Ớ Ờ Ở Ỡ Ợ Ụ Ủ Ứ Ừ Ử Ữ Ự Ỳ Ỵ Ỷ Ỹ
+    (0x1EA0, 0x1EF9),
     ### General Punctuation (core subset) ###
     # Smart quotes, en dash, em dash, ellipsis, NO-BREAK SPACE
     (0x2000, 0x206F),
@@ -102,6 +119,9 @@ intervals = [
     # (0xFE30, 0xFE4F),
     # # CJK Compatibility Ideographs
     # (0xF900, 0xFAFF),
+    ### Alphabetic Presentation Forms (Latin ligatures) ###
+    # ff, fi, fl, ffi, ffl, long-st, st
+    (0xFB00, 0xFB06),
     ### Specials
     # Replacement Character
     (0xFFFD, 0xFFFD),
@@ -117,6 +137,33 @@ def norm_floor(val):
 def norm_ceil(val):
     return int(math.ceil(val / (1 << 6)))
 
+# Fixed-point (fp4) output conventions (must match EpdFontData.h / fp4 namespace):
+#
+#   advanceX    12.4 unsigned fixed-point (uint16_t).
+#               12 integer bits, 4 fractional bits = 1/16-pixel resolution.
+#               Encoded from FreeType's 16.16 linearHoriAdvance.
+#
+#   kernMatrix  4.4 signed fixed-point (int8_t).
+#               4 integer bits, 4 fractional bits = 1/16-pixel resolution.
+#               Range: -8.0 to +7.9375 pixels.
+#               Encoded from font design-unit kerning values.
+#
+# Both share 4 fractional bits so the renderer can add them directly into a
+# single int32_t accumulator and defer rounding until pixel placement.
+
+def fp4_from_ft16_16(val):
+    """Convert FreeType 16.16 fixed-point to 12.4 fixed-point with rounding."""
+    return (val + (1 << 11)) >> 12
+
+def fp4_from_design_units(du, scale):
+    """Convert a font design-unit value to 4.4 fixed-point, clamped to int8_t.
+
+    Multiplies by scale (ppem / units_per_em) and shifts into 4 fractional
+    bits.  The result is rounded to nearest and clamped to [-128, 127].
+    """
+    raw = round(du * scale * 16)
+    return max(-128, min(127, raw))
+
 def chunks(l, n):
     for i in range(0, len(l), n):
         yield l[i:i + n]
@@ -127,10 +174,9 @@ def load_glyph(code_point):
         face = font_stack[face_index]
         glyph_index = face.get_char_index(code_point)
         if glyph_index > 0:
-            face.load_glyph(glyph_index, freetype.FT_LOAD_RENDER)
+            face.load_glyph(glyph_index, load_flags)
             return face
         face_index += 1
-    print(f"code point {code_point} ({hex(code_point)}) not found in font stack!", file=sys.stderr)
     return None
 
 unmerged_intervals = sorted(intervals + add_ints)
@@ -251,7 +297,9 @@ for i_start, i_end in intervals:
         glyph = GlyphProps(
             width = bitmap.width,
             height = bitmap.rows,
-            advance_x = norm_floor(face.glyph.advance.x),
+            # We use linearHoriAdvance (16.16 fixed-point, unhinted) instead of
+            # advance.x (26.6 fixed-point, grid-fitted to whole pixels by hinter)
+            advance_x = fp4_from_ft16_16(face.glyph.linearHoriAdvance),
             left = face.glyph.bitmap_left,
             top = face.glyph.bitmap_top,
             data_length = len(packed),
@@ -271,9 +319,408 @@ for index, glyph in enumerate(all_glyphs):
     glyph_data.extend([b for b in packed])
     glyph_props.append(props)
 
+# --- Kerning pair extraction ---
+# Modern fonts store kerning in the OpenType GPOS table, which FreeType's
+# get_kerning() does not read. We use fonttools to parse both the legacy
+# kern table and the GPOS 'kern' feature (PairPos lookups, including
+# Extension wrappers).
+
+COMBINING_MARKS_START = 0x0300
+COMBINING_MARKS_END = 0x036F
+all_codepoints = [g.code_point for g in glyph_props]
+kernable_codepoints = set(cp for cp in all_codepoints
+                          if not (COMBINING_MARKS_START <= cp <= COMBINING_MARKS_END))
+
+# Map each kernable codepoint to the font-stack index that serves it
+# (same priority logic as load_glyph).
+cp_to_face_idx = {}
+for cp in kernable_codepoints:
+    for face_idx, f in enumerate(font_stack):
+        if f.get_char_index(cp) > 0:
+            cp_to_face_idx[cp] = face_idx
+            break
+
+# Group codepoints by face index
+face_idx_cps = {}
+for cp, fi in cp_to_face_idx.items():
+    face_idx_cps.setdefault(fi, set()).add(cp)
+
+def _extract_pairpos_subtable(subtable, glyph_to_cp, raw_kern):
+    """Extract kerning from a PairPos subtable (Format 1 or 2)."""
+    if subtable.Format == 1:
+        # Individual pairs
+        for i, coverage_glyph in enumerate(subtable.Coverage.glyphs):
+            if coverage_glyph not in glyph_to_cp:
+                continue
+            pair_set = subtable.PairSet[i]
+            for pvr in pair_set.PairValueRecord:
+                if pvr.SecondGlyph not in glyph_to_cp:
+                    continue
+                xa = 0
+                if hasattr(pvr, 'Value1') and pvr.Value1:
+                    xa = getattr(pvr.Value1, 'XAdvance', 0) or 0
+                if xa != 0:
+                    key = (coverage_glyph, pvr.SecondGlyph)
+                    raw_kern[key] = raw_kern.get(key, 0) + xa
+    elif subtable.Format == 2:
+        # Class-based pairs
+        class_def1 = subtable.ClassDef1.classDefs if subtable.ClassDef1 else {}
+        class_def2 = subtable.ClassDef2.classDefs if subtable.ClassDef2 else {}
+        coverage_set = set(subtable.Coverage.glyphs)
+        for left_glyph in glyph_to_cp:
+            if left_glyph not in coverage_set:
+                continue
+            c1 = class_def1.get(left_glyph, 0)
+            if c1 >= len(subtable.Class1Record):
+                continue
+            class1_rec = subtable.Class1Record[c1]
+            for right_glyph in glyph_to_cp:
+                c2 = class_def2.get(right_glyph, 0)
+                if c2 >= len(class1_rec.Class2Record):
+                    continue
+                c2_rec = class1_rec.Class2Record[c2]
+                xa = 0
+                if hasattr(c2_rec, 'Value1') and c2_rec.Value1:
+                    xa = getattr(c2_rec.Value1, 'XAdvance', 0) or 0
+                if xa != 0:
+                    key = (left_glyph, right_glyph)
+                    raw_kern[key] = raw_kern.get(key, 0) + xa
+
+def extract_kerning_fonttools(font_path, codepoints, ppem):
+    """Extract kerning pairs from a font file using fonttools.
+
+    Returns dict of {(leftCp, rightCp): pixel_adjust} for the given
+    codepoints.  Values are scaled from font design units to integer
+    pixels at ppem.
+    """
+    font = TTFont(font_path)
+    units_per_em = font['head'].unitsPerEm
+    cmap = font.getBestCmap() or {}
+
+    # Build glyph_name -> codepoint map (only for requested codepoints)
+    glyph_to_cp = {}
+    for cp in codepoints:
+        gname = cmap.get(cp)
+        if gname:
+            glyph_to_cp[gname] = cp
+
+    # Collect raw kerning values in font design units
+    raw_kern = {}  # (left_glyph_name, right_glyph_name) -> design_units
+
+    # 1. Legacy kern table
+    if 'kern' in font:
+        for subtable in font['kern'].kernTables:
+            if hasattr(subtable, 'kernTable'):
+                for (lg, rg), val in subtable.kernTable.items():
+                    if lg in glyph_to_cp and rg in glyph_to_cp:
+                        raw_kern[(lg, rg)] = raw_kern.get((lg, rg), 0) + val
+
+    # 2. GPOS 'kern' feature
+    if 'GPOS' in font:
+        gpos = font['GPOS'].table
+        kern_lookup_indices = set()
+        if gpos.FeatureList:
+            for fr in gpos.FeatureList.FeatureRecord:
+                if fr.FeatureTag == 'kern':
+                    kern_lookup_indices.update(fr.Feature.LookupListIndex)
+        for li in kern_lookup_indices:
+            lookup = gpos.LookupList.Lookup[li]
+            for st in lookup.SubTable:
+                actual = st
+                # Unwrap Extension (lookup type 9) wrappers
+                if lookup.LookupType == 9 and hasattr(st, 'ExtSubTable'):
+                    actual = st.ExtSubTable
+                if hasattr(actual, 'Format'):
+                    _extract_pairpos_subtable(actual, glyph_to_cp, raw_kern)
+
+    font.close()
+
+    # Scale design-unit kerning values to 4.4 fixed-point pixels.
+    scale = ppem / units_per_em
+    result = {}  # (leftCp, rightCp) -> 4.4 fixed-point adjust
+    for (lg, rg), du in raw_kern.items():
+        lcp = glyph_to_cp[lg]
+        rcp = glyph_to_cp[rg]
+        adjust = fp4_from_design_units(du, scale)
+        if adjust != 0:
+            result[(lcp, rcp)] = adjust
+    return result
+
+# The ppem used by the existing glyph rasterization:
+#   face.set_char_size(size << 6, size << 6, 150, 150)
+# means size_pt at 150 DPI -> ppem = size * 150 / 72
+ppem = size * 150.0 / 72.0
+
+kern_map = {}  # (leftCp, rightCp) -> adjust
+for face_idx, cps in face_idx_cps.items():
+    font_path = args.fontstack[face_idx]
+    kern_map.update(extract_kerning_fonttools(font_path, cps, ppem))
+
+print(f"kerning: {len(kern_map)} pairs extracted", file=sys.stderr)
+
+# --- Derive class-based kerning from pairs ---
+kern_left_classes = []   # list of (codepoint, classId)
+kern_right_classes = []  # list of (codepoint, classId)
+kern_matrix = []         # flat list of int8_t values
+kern_left_class_count = 0
+kern_right_class_count = 0
+
+if kern_map:
+    all_left_cps = {lcp for lcp, _ in kern_map}
+    all_right_cps = {rcp for _, rcp in kern_map}
+
+    sorted_right_cps = sorted(all_right_cps)
+    sorted_left_cps = sorted(all_left_cps)
+
+    # Group left codepoints by identical adjustment row
+    left_profile_to_class = {}
+    left_class_map = {}
+    left_class_id = 1
+    for lcp in sorted(all_left_cps):
+        row = tuple(kern_map.get((lcp, rcp), 0) for rcp in sorted_right_cps)
+        if row not in left_profile_to_class:
+            left_profile_to_class[row] = left_class_id
+            left_class_id += 1
+        left_class_map[lcp] = left_profile_to_class[row]
+
+    # Group right codepoints by identical adjustment column
+    right_profile_to_class = {}
+    right_class_map = {}
+    right_class_id = 1
+    for rcp in sorted(all_right_cps):
+        col = tuple(kern_map.get((lcp, rcp), 0) for lcp in sorted_left_cps)
+        if col not in right_profile_to_class:
+            right_profile_to_class[col] = right_class_id
+            right_class_id += 1
+        right_class_map[rcp] = right_profile_to_class[col]
+
+    kern_left_class_count = left_class_id - 1
+    kern_right_class_count = right_class_id - 1
+
+    if kern_left_class_count > 255 or kern_right_class_count > 255:
+        print(f"WARNING: kerning class count exceeds uint8_t range "
+              f"(left={kern_left_class_count}, right={kern_right_class_count})",
+              file=sys.stderr)
+
+    # Build the class x class matrix
+    kern_matrix = [0] * (kern_left_class_count * kern_right_class_count)
+    for (lcp, rcp), adjust in kern_map.items():
+        lc = left_class_map[lcp] - 1
+        rc = right_class_map[rcp] - 1
+        kern_matrix[lc * kern_right_class_count + rc] = adjust
+
+    # Build sorted class entry lists
+    kern_left_classes = sorted(left_class_map.items())
+    kern_right_classes = sorted(right_class_map.items())
+
+    matrix_size = kern_left_class_count * kern_right_class_count
+    entries_size = (len(kern_left_classes) + len(kern_right_classes)) * 3
+    print(f"kerning: {kern_left_class_count} left classes, {kern_right_class_count} right classes, "
+          f"{matrix_size + entries_size} bytes", file=sys.stderr)
+
+# --- Ligature pair extraction ---
+# Parse the OpenType GSUB table for LigatureSubst (type 4) lookups.
+# Multi-character ligatures (3+ codepoints) are decomposed into chained
+# pairs when an intermediate ligature exists (e.g., ffi = ff + i where ff
+# is itself a ligature). Only pairs where both input codepoints and the
+# output codepoint are in the generated glyph set are included.
+
+all_codepoints_set = set(all_codepoints)
+
+# Standard Unicode ligature codepoints for known input sequences.
+# Used as a fallback when the GSUB substitute glyph has no cmap entry.
+STANDARD_LIGATURE_MAP = {
+    (0x66, 0x66):       0xFB00,  # ff
+    (0x66, 0x69):       0xFB01,  # fi
+    (0x66, 0x6C):       0xFB02,  # fl
+    (0x66, 0x66, 0x69): 0xFB03,  # ffi
+    (0x66, 0x66, 0x6C): 0xFB04,  # ffl
+    (0x17F, 0x74):      0xFB05,  # long-s + t
+    (0x73, 0x74):       0xFB06,  # st
+}
+
+def extract_ligatures_fonttools(font_path, codepoints):
+    """Extract ligature substitution pairs from a font file using fonttools.
+
+    Returns list of (packed_pair, ligature_codepoint) for the given codepoints.
+    Multi-character ligatures are decomposed into chained pairs.
+    """
+    font = TTFont(font_path)
+    cmap = font.getBestCmap() or {}
+
+    # Build glyph_name -> codepoint and codepoint -> glyph_name maps
+    glyph_to_cp = {}
+    cp_to_glyph = {}
+    for cp, gname in cmap.items():
+        glyph_to_cp[gname] = cp
+        cp_to_glyph[cp] = gname
+
+    # Collect raw ligature rules: (sequence_of_codepoints) -> ligature_codepoint
+    raw_ligatures = {}  # tuple of codepoints -> ligature codepoint
+
+    if 'GSUB' in font:
+        gsub = font['GSUB'].table
+
+        # Find lookup indices for ligature features.
+        # Currently extracts 'liga' (standard) and 'rlig' (required) only.
+        # To also extract discretionary or historical ligatures, add:
+        #   'dlig' - Discretionary Ligatures (e.g., ft, st in Bookerly)
+        #   'hlig' - Historical Ligatures (e.g., long-s+t in OpenDyslexic)
+        # These are off by default in standard text renderers.
+        LIGATURE_FEATURES = ('liga', 'rlig')
+        liga_lookup_indices = set()
+        if gsub.FeatureList:
+            for fr in gsub.FeatureList.FeatureRecord:
+                if fr.FeatureTag in LIGATURE_FEATURES:
+                    liga_lookup_indices.update(fr.Feature.LookupListIndex)
+
+        for li in liga_lookup_indices:
+            lookup = gsub.LookupList.Lookup[li]
+            for st in lookup.SubTable:
+                actual = st
+                # Unwrap Extension (lookup type 7) wrappers
+                if lookup.LookupType == 7 and hasattr(st, 'ExtSubTable'):
+                    actual = st.ExtSubTable
+                # LigatureSubst is lookup type 4
+                if not hasattr(actual, 'ligatures'):
+                    continue
+                for first_glyph, ligature_list in actual.ligatures.items():
+                    if first_glyph not in glyph_to_cp:
+                        continue
+                    first_cp = glyph_to_cp[first_glyph]
+                    for lig in ligature_list:
+                        # lig.Component is a list of subsequent glyph names
+                        # lig.LigGlyph is the substitute glyph name
+                        component_cps = []
+                        valid = True
+                        for comp_glyph in lig.Component:
+                            if comp_glyph not in glyph_to_cp:
+                                valid = False
+                                break
+                            component_cps.append(glyph_to_cp[comp_glyph])
+                        if not valid:
+                            continue
+                        seq = tuple([first_cp] + component_cps)
+                        if lig.LigGlyph in glyph_to_cp:
+                            lig_cp = glyph_to_cp[lig.LigGlyph]
+                        elif seq in STANDARD_LIGATURE_MAP:
+                            lig_cp = STANDARD_LIGATURE_MAP[seq]
+                        else:
+                            seq_str = ', '.join(f'U+{cp:04X}' for cp in seq)
+                            print(f"ligatures: WARNING: dropping ligature ({seq_str}) -> "
+                                  f"glyph '{lig.LigGlyph}': output glyph has no cmap entry "
+                                  f"and input sequence is not in STANDARD_LIGATURE_MAP",
+                                  file=sys.stderr)
+                            continue
+                        raw_ligatures[seq] = lig_cp
+
+    font.close()
+
+    # Filter: only keep ligatures where all input and output codepoints are
+    # in our generated glyph set
+    filtered = {}
+    for seq, lig_cp in raw_ligatures.items():
+        if lig_cp not in codepoints and lig_cp not in all_codepoints_set:
+            continue
+        if all(cp in codepoints for cp in seq):
+            filtered[seq] = lig_cp
+
+    # Decompose into chained pairs
+    # For 2-codepoint sequences: direct pair (a, b) -> lig
+    # For 3+ codepoint sequences: chain through intermediates
+    #   e.g., (f, f, i) -> ffi requires (f, f) -> ff to exist,
+    #   then we add (ff, i) -> ffi
+    pairs = []
+    # First pass: collect all 2-codepoint ligatures
+    two_char = {seq: lig_cp for seq, lig_cp in filtered.items() if len(seq) == 2}
+    for seq, lig_cp in two_char.items():
+        packed = (seq[0] << 16) | seq[1]
+        pairs.append((packed, lig_cp))
+
+    # Second pass: decompose 3+ codepoint ligatures into chained pairs
+    for seq, lig_cp in filtered.items():
+        if len(seq) < 3:
+            continue
+        # Try to find an intermediate: check if the first N-1 codepoints
+        # form a known ligature, then chain (intermediate, last) -> lig
+        prefix = seq[:-1]
+        last_cp = seq[-1]
+        if prefix in filtered:
+            intermediate_cp = filtered[prefix]
+            packed = (intermediate_cp << 16) | last_cp
+            pairs.append((packed, lig_cp))
+        else:
+            print(f"ligatures: skipping {len(seq)}-char ligature "
+                  f"({', '.join(f'U+{cp:04X}' for cp in seq)}) -> U+{lig_cp:04X}: "
+                  f"no intermediate ligature for prefix", file=sys.stderr)
+
+    return pairs
+
+ligature_codepoints = set(cp for cp in all_codepoints
+                          if not (COMBINING_MARKS_START <= cp <= COMBINING_MARKS_END))
+
+# Map ligature codepoints to the font-stack index that serves them
+lig_cp_to_face_idx = {}
+for cp in ligature_codepoints:
+    for face_idx, f in enumerate(font_stack):
+        if f.get_char_index(cp) > 0:
+            lig_cp_to_face_idx[cp] = face_idx
+            break
+
+# Group by face index
+lig_face_idx_cps = {}
+for cp, fi in lig_cp_to_face_idx.items():
+    lig_face_idx_cps.setdefault(fi, set()).add(cp)
+
+ligature_pairs = []
+for face_idx, cps in lig_face_idx_cps.items():
+    font_path = args.fontstack[face_idx]
+    ligature_pairs.extend(extract_ligatures_fonttools(font_path, cps))
+
+# Deduplicate (keep first occurrence) and sort
+seen_lig_keys = set()
+unique_ligature_pairs = []
+for packed, lig_cp in ligature_pairs:
+    if packed not in seen_lig_keys:
+        seen_lig_keys.add(packed)
+        unique_ligature_pairs.append((packed, lig_cp))
+ligature_pairs = sorted(unique_ligature_pairs, key=lambda p: p[0])
+print(f"ligatures: {len(ligature_pairs)} pairs extracted", file=sys.stderr)
+
 compress = args.compress
 
+
+def to_byte_aligned(packed, width, height):
+    """Convert packed 2-bit bitmap to byte-aligned format (rows padded to byte boundary).
+
+    In packed format, pixels flow continuously across row boundaries (4 pixels/byte).
+    In byte-aligned format, each row starts at a byte boundary, padding the last byte
+    of each row with zero bits if width % 4 != 0. This improves DEFLATE compression
+    because identical pixel rows produce identical byte patterns regardless of position.
+    """
+    if width == 0 or height == 0:
+        return b''
+    row_stride = (width + 3) // 4  # bytes per byte-aligned row
+    aligned = bytearray(row_stride * height)
+    for y in range(height):
+        for x in range(width):
+            # Read pixel from packed format (continuous bit stream)
+            packed_pos = y * width + x
+            packed_byte_idx = packed_pos // 4
+            packed_shift = (3 - (packed_pos % 4)) * 2
+            pixel = (packed[packed_byte_idx] >> packed_shift) & 0x3
+
+            # Write pixel to byte-aligned format (row-aligned)
+            aligned_byte_idx = y * row_stride + x // 4
+            aligned_shift = (3 - (x % 4)) * 2
+            aligned[aligned_byte_idx] |= (pixel << aligned_shift)
+    return bytes(aligned)
+
+
 # Build groups for compression
+if compress and not is2Bit:
+    print("Error: --compress requires --2bit (byte-aligned compression only supports 2-bit format)", file=sys.stderr)
+    sys.exit(1)
 if compress:
     # Script-based grouping: glyphs that co-occur in typical text rendering
     # are grouped together for efficient LRU caching on the embedded target.
@@ -283,13 +730,16 @@ if compress:
         (0x0000, 0x007F),   # ASCII
         (0x0080, 0x00FF),   # Latin-1 Supplement
         (0x0100, 0x017F),   # Latin Extended-A
+        (0x0180, 0x024F),   # Latin Extended-B
         (0x0300, 0x036F),   # Combining Diacritical Marks
         (0x0400, 0x04FF),   # Cyrillic
+        (0x1EA0, 0x1EF9),   # Vietnamese Extended
         (0x2000, 0x206F),   # General Punctuation
         (0x2070, 0x209F),   # Superscripts & Subscripts
         (0x20A0, 0x20CF),   # Currency Symbols
         (0x2190, 0x21FF),   # Arrows
         (0x2200, 0x22FF),   # Math Operators
+        (0xFB00, 0xFB06),   # Alphabetic Presentation Forms (ligatures)
         (0xFFFD, 0xFFFD),   # Replacement Character
     ]
 
@@ -328,11 +778,12 @@ if compress:
 
     for first_idx, count in groups:
         # Concatenate bitmap data for this group
-        group_data = b''
+        packed_len = 0
+        group_aligned = bytearray()
         for gi in range(first_idx, first_idx + count):
             props, packed = all_glyphs[gi]
-            # Update glyph's dataOffset to be within-group offset
-            within_group_offset = len(group_data)
+            # Update glyph's dataOffset to be within-group offset (packed offset)
+            within_group_offset = packed_len
             old_props = modified_glyph_props[gi]
             modified_glyph_props[gi] = GlyphProps(
                 width=old_props.width,
@@ -344,13 +795,14 @@ if compress:
                 data_offset=within_group_offset,
                 code_point=old_props.code_point,
             )
-            group_data += packed
+            packed_len += len(packed)
+            group_aligned.extend(to_byte_aligned(packed, old_props.width, old_props.height))
 
-        # Compress with raw DEFLATE (no zlib/gzip header)
+        # Compress byte-aligned data with raw DEFLATE (no zlib/gzip header)
         compressor = zlib.compressobj(level=9, wbits=-15)
-        compressed = compressor.compress(group_data) + compressor.flush()
+        compressed = compressor.compress(bytes(group_aligned)) + compressor.flush()
 
-        compressed_groups.append((compressed, len(group_data), count, first_idx))
+        compressed_groups.append((compressed, len(group_aligned), count, first_idx))
         compressed_bitmap_data.extend(compressed)
         compressed_offset += len(compressed)
 
@@ -381,9 +833,14 @@ else:
         print ("    " + " ".join(f"0x{b:02X}," for b in c))
     print ("};\n");
 
+def cp_label(cp):
+    if cp == 0x5C:
+        return '<backslash>'
+    return chr(cp) if 0x20 < cp < 0x7F else f'U+{cp:04X}'
+
 print(f"static const EpdGlyph {font_name}Glyphs[] = {{")
 for i, g in enumerate(glyph_props):
-    print ("    { " + ", ".join([f"{a}" for a in list(g[:-1])]),"},", f"// {chr(g.code_point) if g.code_point != 92 else '<backslash>'}")
+    print ("    { " + ", ".join([f"{a}" for a in list(g[:-1])]),"},", f"// {cp_label(g.code_point)}")
 print ("};\n");
 
 print(f"static const EpdUnicodeInterval {font_name}Intervals[] = {{")
@@ -401,6 +858,30 @@ if compress:
         compressed_offset += len(compressed)
     print("};\n")
 
+if kern_map:
+    print(f"static const EpdKernClassEntry {font_name}KernLeftClasses[] = {{")
+    for cp, cls in kern_left_classes:
+        print(f"    {{ 0x{cp:04X}, {cls} }}, // {cp_label(cp)}")
+    print("};\n")
+
+    print(f"static const EpdKernClassEntry {font_name}KernRightClasses[] = {{")
+    for cp, cls in kern_right_classes:
+        print(f"    {{ 0x{cp:04X}, {cls} }}, // {cp_label(cp)}")
+    print("};\n")
+
+    print(f"static const int8_t {font_name}KernMatrix[] = {{")
+    for row in range(kern_left_class_count):
+        row_start = row * kern_right_class_count
+        row_vals = kern_matrix[row_start:row_start + kern_right_class_count]
+        print("    " + ", ".join(f"{v:4d}" for v in row_vals) + ",")
+    print("};\n")
+
+if ligature_pairs:
+    print(f"static const EpdLigaturePair {font_name}LigaturePairs[] = {{")
+    for packed_pair, lig_cp in ligature_pairs:
+        print(f"    {{ 0x{packed_pair:08X}, 0x{lig_cp:04X} }}, // {cp_label(packed_pair >> 16)} {cp_label(packed_pair & 0xFFFF)} -> {cp_label(lig_cp)}")
+    print("};\n")
+
 print(f"static const EpdFontData {font_name} = {{")
 print(f"    {font_name}Bitmaps,")
 print(f"    {font_name}Glyphs,")
@@ -413,6 +894,30 @@ print(f"    {'true' if is2Bit else 'false'},")
 if compress:
     print(f"    {font_name}Groups,")
     print(f"    {len(compressed_groups)},")
+else:
+    print("    nullptr,")
+    print("    0,")
+# glyphToGroup (not used for script-grouped fonts)
+print("    nullptr,")
+if kern_map:
+    print(f"    {font_name}KernLeftClasses,")
+    print(f"    {font_name}KernRightClasses,")
+    print(f"    {font_name}KernMatrix,")
+    print(f"    {len(kern_left_classes)},")
+    print(f"    {len(kern_right_classes)},")
+    print(f"    {kern_left_class_count},")
+    print(f"    {kern_right_class_count},")
+else:
+    print(f"    nullptr,")
+    print(f"    nullptr,")
+    print(f"    nullptr,")
+    print(f"    0,")
+    print(f"    0,")
+    print(f"    0,")
+    print(f"    0,")
+if ligature_pairs:
+    print(f"    {font_name}LigaturePairs,")
+    print(f"    {len(ligature_pairs)},")
 else:
     print(f"    nullptr,")
     print(f"    0,")

lib/EpdFont/scripts/verify_compression.py

@@ -3,9 +3,13 @@
 Round-trip verification for compressed font headers.
 
 Parses each generated .h file in the given directory, identifies compressed fonts
-(those with a Groups array), decompresses each group, and verifies that
-decompression succeeds and all glyph offsets/lengths fall within bounds.
+(those with a Groups array), decompresses each group (byte-aligned bitmap format),
+compacts to packed format, and verifies the data matches expected glyph sizes.
+
+Supports both contiguous-group fonts (Latin) and frequency-grouped fonts (CJK)
+with glyphToGroup mapping arrays.
 """
+import math
 import os
 import re
 import sys
@@ -18,6 +22,11 @@ def parse_hex_array(text):
     return bytes(int(h, 16) for h in hex_vals)
 
 
+def parse_uint8_array(text):
+    """Extract uint8/uint16 values from a C array string like '{ 0, 1, 0xFF, ... }'"""
+    return [int(v, 0) for v in re.findall(r'\b0x[0-9A-Fa-f]+\b|\b\d+\b', text)]
+
+
 def parse_groups(text):
     """Parse EpdFontGroup array entries: { compressedOffset, compressedSize, uncompressedSize, glyphCount, firstGlyphIndex }"""
     groups = []
@@ -48,6 +57,45 @@ def parse_glyphs(text):
     return glyphs
 
 
+def get_group_glyph_indices(group, group_index, glyphs, glyph_to_group):
+    """Get the ordered list of glyph indices belonging to a group."""
+    if glyph_to_group is not None:
+        # Frequency-grouped: scan all glyphs
+        return [i for i in range(len(glyphs)) if glyph_to_group[i] == group_index]
+    else:
+        # Contiguous: sequential from firstGlyphIndex
+        first = group['firstGlyphIndex']
+        return list(range(first, first + group['glyphCount']))
+
+
+def compact_aligned_to_packed(aligned_data, width, height):
+    """Convert byte-aligned 2-bit bitmap to packed format (reverse of to_byte_aligned).
+
+    In byte-aligned format, each row starts at a byte boundary.
+    In packed format, pixels flow continuously across row boundaries (4 pixels/byte).
+    """
+    if width == 0 or height == 0:
+        return b''
+    packed_size = math.ceil(width * height / 4)
+    packed = bytearray(packed_size)
+    row_stride = (width + 3) // 4  # bytes per byte-aligned row
+
+    for y in range(height):
+        for x in range(width):
+            # Read pixel from byte-aligned format (row-aligned)
+            aligned_byte_idx = y * row_stride + x // 4
+            aligned_shift = (3 - (x % 4)) * 2
+            pixel = (aligned_data[aligned_byte_idx] >> aligned_shift) & 0x3
+
+            # Write pixel to packed format (continuous bit stream)
+            packed_pos = y * width + x
+            packed_byte_idx = packed_pos // 4
+            packed_shift = (3 - (packed_pos % 4)) * 2
+            packed[packed_byte_idx] |= (pixel << packed_shift)
+
+    return bytes(packed)
+
+
 def verify_font_file(filepath):
     """Verify a single font header file. Returns (font_name, success, message)."""
     with open(filepath, 'r') as f:
@@ -92,6 +140,20 @@ def verify_font_file(filepath):
 
     glyphs = parse_glyphs(glyphs_match.group(1))
 
+    # Check for glyphToGroup array (frequency-grouped fonts)
+    glyph_to_group = None
+    g2g_match = re.search(
+        r'static const uint16_t ' + re.escape(font_name) + r'GlyphToGroup\[\]\s*=\s*\{(.+?)\};',
+        content, re.DOTALL
+    )
+    if g2g_match:
+        glyph_to_group = parse_uint8_array(g2g_match.group(1))
+        if len(glyph_to_group) != len(glyphs):
+            return (font_name, False, f"glyphToGroup length ({len(glyph_to_group)}) != glyph count ({len(glyphs)})")
+        max_group_id = max(glyph_to_group)
+        if max_group_id >= len(groups):
+            return (font_name, False, f"glyphToGroup contains group ID {max_group_id} but only {len(groups)} groups exist")
+
     # Verify each group
     for gi, group in enumerate(groups):
         # Extract compressed chunk
@@ -99,7 +161,7 @@ def verify_font_file(filepath):
         if len(chunk) != group['compressedSize']:
             return (font_name, False, f"group {gi}: compressed data truncated (expected {group['compressedSize']}, got {len(chunk)})")
 
-        # Decompress with raw DEFLATE
+        # Decompress with raw DEFLATE — result is byte-aligned data
         try:
             decompressed = zlib.decompress(chunk, -15)
         except zlib.error as e:
@@ -108,22 +170,64 @@ def verify_font_file(filepath):
         if len(decompressed) != group['uncompressedSize']:
             return (font_name, False, f"group {gi}: size mismatch (expected {group['uncompressedSize']}, got {len(decompressed)})")
 
-        # Verify each glyph's data within the group
-        first = group['firstGlyphIndex']
-        for j in range(group['glyphCount']):
-            glyph_idx = first + j
+        # Get glyph indices for this group
+        group_glyph_indices = get_group_glyph_indices(group, gi, glyphs, glyph_to_group)
+        if glyph_to_group is not None and len(group_glyph_indices) != group['glyphCount']:
+            return (font_name, False,
+                    f"group {gi}: glyphCount {group['glyphCount']} != mapping count {len(group_glyph_indices)}")
+
+        # Walk through byte-aligned data, compact each glyph, and verify against packed format
+        byte_aligned_offset = 0
+        packed_offset = 0
+
+        for glyph_idx in group_glyph_indices:
             if glyph_idx >= len(glyphs):
                 return (font_name, False, f"group {gi}: glyph index {glyph_idx} out of range")
-
             glyph = glyphs[glyph_idx]
-            offset = glyph['dataOffset']
-            length = glyph['dataLength']
+            width = glyph['width']
+            height = glyph['height']
 
-            if offset + length > len(decompressed):
-                return (font_name, False, f"group {gi}, glyph {glyph_idx}: data extends beyond decompressed buffer "
-                        f"(offset={offset}, length={length}, decompressed_size={len(decompressed)})")
+            if width == 0 or height == 0:
+                # Zero-size glyphs should have dataOffset == current packed_offset and dataLength == 0
+                if glyph['dataOffset'] != packed_offset:
+                    return (font_name, False, f"group {gi}, glyph {glyph_idx}: zero-size glyph dataOffset {glyph['dataOffset']} != expected packed offset {packed_offset}")
+                if glyph['dataLength'] != 0:
+                    return (font_name, False, f"group {gi}, glyph {glyph_idx}: zero-size glyph dataLength {glyph['dataLength']} != expected 0")
+                continue
 
-    return (font_name, True, f"{len(groups)} groups, {len(glyphs)} glyphs OK")
+            aligned_size = ((width + 3) // 4) * height
+            packed_size = math.ceil(width * height / 4)
+
+            # Verify packed offset and size match glyph metadata
+            if glyph['dataOffset'] != packed_offset:
+                return (font_name, False, f"group {gi}, glyph {glyph_idx}: dataOffset {glyph['dataOffset']} != expected packed offset {packed_offset}")
+            if glyph['dataLength'] != packed_size:
+                return (font_name, False, f"group {gi}, glyph {glyph_idx}: dataLength {glyph['dataLength']} != expected packed length {packed_size} "
+                        f"(width={width}, height={height})")
+
+            # Extract byte-aligned data for this glyph
+            if byte_aligned_offset + aligned_size > len(decompressed):
+                return (font_name, False, f"group {gi}, glyph {glyph_idx}: byte-aligned data extends beyond decompressed buffer "
+                        f"(offset={byte_aligned_offset}, size={aligned_size}, buf_size={len(decompressed)})")
+
+            aligned_glyph = decompressed[byte_aligned_offset:byte_aligned_offset + aligned_size]
+
+            # Compact to packed and verify pixel values are valid (0-3 for 2-bit)
+            packed_glyph = compact_aligned_to_packed(aligned_glyph, width, height)
+            if len(packed_glyph) != packed_size:
+                return (font_name, False, f"group {gi}, glyph {glyph_idx}: compacted size {len(packed_glyph)} != expected {packed_size}")
+
+            byte_aligned_offset += aligned_size
+            packed_offset += packed_size
+
+        # Verify total byte-aligned size matches uncompressedSize
+        if byte_aligned_offset != group['uncompressedSize']:
+            return (font_name, False, f"group {gi}: total byte-aligned size {byte_aligned_offset} != uncompressedSize {group['uncompressedSize']}")
+
+    extra_info = ""
+    if glyph_to_group is not None:
+        extra_info = " (frequency-grouped)"
+    return (font_name, True, f"{len(groups)} groups, {len(glyphs)} glyphs OK{extra_info}")
 
 
 def main():

lib/Epub/Epub.cpp

@@ -103,14 +103,11 @@ bool Epub::parseContentOpf(BookMetadataCache::BookMetadata& bookMetadata) {
           pos += strlen(pattern);
           const auto endPos = coverPageHtml.find('"', pos);
           if (endPos != std::string::npos) {
-            const auto ref = coverPageHtml.substr(pos, endPos - pos);
+            const auto ref = std::string_view{coverPageHtml}.substr(pos, endPos - pos);
             // Check if it's an image file
-            if (ref.length() >= 4) {
-              const auto ext = ref.substr(ref.length() - 4);
-              if (ext == ".png" || ext == ".jpg" || ext == "jpeg" || ext == ".gif") {
-                imageRef = ref;
-                break;
-              }
+            if (FsHelpers::hasPngExtension(ref) || FsHelpers::hasJpgExtension(ref) || FsHelpers::hasGifExtension(ref)) {
+              imageRef = ref;
+              break;
             }
           }
           pos = coverPageHtml.find(pattern, pos);
@@ -541,8 +538,7 @@ bool Epub::generateCoverBmp(bool cropped) const {
     return false;
   }
 
-  if (coverImageHref.substr(coverImageHref.length() - 4) == ".jpg" ||
-      coverImageHref.substr(coverImageHref.length() - 5) == ".jpeg") {
+  if (FsHelpers::hasJpgExtension(coverImageHref)) {
     LOG_DBG("EBP", "Generating BMP from JPG cover image (%s mode)", cropped ? "cropped" : "fit");
     const auto coverJpgTempPath = getCachePath() + "/.cover.jpg";
 
@@ -575,7 +571,7 @@ bool Epub::generateCoverBmp(bool cropped) const {
     return success;
   }
 
-  if (coverImageHref.substr(coverImageHref.length() - 4) == ".png") {
+  if (FsHelpers::hasPngExtension(coverImageHref)) {
     LOG_DBG("EBP", "Generating BMP from PNG cover image (%s mode)", cropped ? "cropped" : "fit");
     const auto coverPngTempPath = getCachePath() + "/.cover.png";
 
@@ -629,8 +625,7 @@ bool Epub::generateThumbBmp(int height) const {
   const auto coverImageHref = bookMetadataCache->coreMetadata.coverItemHref;
   if (coverImageHref.empty()) {
     LOG_DBG("EBP", "No known cover image for thumbnail");
-  } else if (coverImageHref.substr(coverImageHref.length() - 4) == ".jpg" ||
-             coverImageHref.substr(coverImageHref.length() - 5) == ".jpeg") {
+  } else if (FsHelpers::hasJpgExtension(coverImageHref)) {
     LOG_DBG("EBP", "Generating thumb BMP from JPG cover image");
     const auto coverJpgTempPath = getCachePath() + "/.cover.jpg";
 
@@ -666,7 +661,7 @@ bool Epub::generateThumbBmp(int height) const {
     }
     LOG_DBG("EBP", "Generated thumb BMP from JPG cover image, success: %s", success ? "yes" : "no");
     return success;
-  } else if (coverImageHref.substr(coverImageHref.length() - 4) == ".png") {
+  } else if (FsHelpers::hasPngExtension(coverImageHref)) {
     LOG_DBG("EBP", "Generating thumb BMP from PNG cover image");
     const auto coverPngTempPath = getCachePath() + "/.cover.png";
 
@@ -858,3 +853,30 @@ float Epub::calculateProgress(const int currentSpineIndex, const float currentSp
   const float totalProgress = static_cast<float>(prevChapterSize) + sectionProgSize;
   return totalProgress / static_cast<float>(bookSize);
 }
+
+int Epub::resolveHrefToSpineIndex(const std::string& href) const {
+  if (!bookMetadataCache || !bookMetadataCache->isLoaded()) return -1;
+
+  // Extract filename (remove #anchor)
+  std::string target = href;
+  size_t hashPos = target.find('#');
+  if (hashPos != std::string::npos) target = target.substr(0, hashPos);
+
+  // Same-file reference (anchor-only)
+  if (target.empty()) return -1;
+
+  // Extract just the filename for comparison
+  size_t targetSlash = target.find_last_of('/');
+  std::string targetFilename = (targetSlash != std::string::npos) ? target.substr(targetSlash + 1) : target;
+
+  for (int i = 0; i < getSpineItemsCount(); i++) {
+    const auto& spineHref = getSpineItem(i).href;
+    // Try exact match first
+    if (spineHref == target) return i;
+    // Then filename-only match
+    size_t spineSlash = spineHref.find_last_of('/');
+    std::string spineFilename = (spineSlash != std::string::npos) ? spineHref.substr(spineSlash + 1) : spineHref;
+    if (spineFilename == targetFilename) return i;
+  }
+  return -1;
+}

lib/Epub/Epub.h

@@ -72,4 +72,5 @@ class Epub {
   size_t getBookSize() const;
   float calculateProgress(int currentSpineIndex, float currentSpineRead) const;
   CssParser* getCssParser() const { return cssParser.get(); }
+  int resolveHrefToSpineIndex(const std::string& href) const;
 };

lib/Epub/Epub/BookMetadataCache.cpp

@@ -274,11 +274,13 @@ bool BookMetadataCache::buildBookBin(const std::string& epubPath, const BookMeta
 }
 
 bool BookMetadataCache::cleanupTmpFiles() const {
-  if (Storage.exists((cachePath + tmpSpineBinFile).c_str())) {
-    Storage.remove((cachePath + tmpSpineBinFile).c_str());
+  const auto spineBinFile = cachePath + tmpSpineBinFile;
+  if (Storage.exists(spineBinFile.c_str())) {
+    Storage.remove(spineBinFile.c_str());
   }
-  if (Storage.exists((cachePath + tmpTocBinFile).c_str())) {
-    Storage.remove((cachePath + tmpTocBinFile).c_str());
+  const auto tocBinFile = cachePath + tmpTocBinFile;
+  if (Storage.exists(tocBinFile.c_str())) {
+    Storage.remove(tocBinFile.c_str());
   }
   return true;
 }

lib/Epub/Epub/FootnoteEntry.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <cstring>
+
+struct FootnoteEntry {
+  char number[24];
+  char href[64];
+
+  FootnoteEntry() {
+    number[0] = '\0';
+    href[0] = '\0';
+  }
+};

lib/Epub/Epub/Page.cpp

@@ -67,6 +67,18 @@ bool Page::serialize(FsFile& file) const {
     }
   }
 
+  // Serialize footnotes (clamp to MAX_FOOTNOTES_PER_PAGE to match addFootnote/deserialize limits)
+  const uint16_t fnCount = std::min<uint16_t>(footnotes.size(), MAX_FOOTNOTES_PER_PAGE);
+  serialization::writePod(file, fnCount);
+  for (uint16_t i = 0; i < fnCount; i++) {
+    const auto& fn = footnotes[i];
+    if (file.write(fn.number, sizeof(fn.number)) != sizeof(fn.number) ||
+        file.write(fn.href, sizeof(fn.href)) != sizeof(fn.href)) {
+      LOG_ERR("PGE", "Failed to write footnote");
+      return false;
+    }
+  }
+
   return true;
 }
 
@@ -92,5 +104,24 @@ std::unique_ptr<Page> Page::deserialize(FsFile& file) {
     }
   }
 
+  // Deserialize footnotes
+  uint16_t fnCount;
+  serialization::readPod(file, fnCount);
+  if (fnCount > MAX_FOOTNOTES_PER_PAGE) {
+    LOG_ERR("PGE", "Invalid footnote count %u", fnCount);
+    return nullptr;
+  }
+  page->footnotes.resize(fnCount);
+  for (uint16_t i = 0; i < fnCount; i++) {
+    auto& entry = page->footnotes[i];
+    if (file.read(entry.number, sizeof(entry.number)) != sizeof(entry.number) ||
+        file.read(entry.href, sizeof(entry.href)) != sizeof(entry.href)) {
+      LOG_ERR("PGE", "Failed to read footnote %u", i);
+      return nullptr;
+    }
+    entry.number[sizeof(entry.number) - 1] = '\0';
+    entry.href[sizeof(entry.href) - 1] = '\0';
+  }
+
   return page;
 }

lib/Epub/Epub/Page.h

@@ -2,9 +2,11 @@
 #include <HalStorage.h>
 
 #include <algorithm>
+#include <string>
 #include <utility>
 #include <vector>
 
+#include "FootnoteEntry.h"
 #include "blocks/ImageBlock.h"
 #include "blocks/TextBlock.h"
 
@@ -32,6 +34,7 @@ class PageLine final : public PageElement {
  public:
   PageLine(std::shared_ptr<TextBlock> block, const int16_t xPos, const int16_t yPos)
       : PageElement(xPos, yPos), block(std::move(block)) {}
+  const std::shared_ptr<TextBlock>& getBlock() const { return block; }
   void render(GfxRenderer& renderer, int fontId, int xOffset, int yOffset) override;
   bool serialize(FsFile& file) override;
   PageElementTag getTag() const override { return TAG_PageLine; }
@@ -56,6 +59,19 @@ class Page {
  public:
   // the list of block index and line numbers on this page
   std::vector<std::shared_ptr<PageElement>> elements;
+  std::vector<FootnoteEntry> footnotes;
+  static constexpr uint16_t MAX_FOOTNOTES_PER_PAGE = 16;
+
+  void addFootnote(const char* number, const char* href) {
+    if (footnotes.size() >= MAX_FOOTNOTES_PER_PAGE) return;  // Cap per-page footnotes
+    FootnoteEntry entry;
+    strncpy(entry.number, number, sizeof(entry.number) - 1);
+    entry.number[sizeof(entry.number) - 1] = '\0';
+    strncpy(entry.href, href, sizeof(entry.href) - 1);
+    entry.href[sizeof(entry.href) - 1] = '\0';
+    footnotes.push_back(entry);
+  }
+
   void render(GfxRenderer& renderer, int fontId, int xOffset, int yOffset) const;
   bool serialize(FsFile& file) const;
   static std::unique_ptr<Page> deserialize(FsFile& file);

lib/Epub/Epub/ParsedText.cpp

@@ -1,11 +1,11 @@
 #include "ParsedText.h"
 
 #include <GfxRenderer.h>
+#include <Utf8.h>
 
 #include <algorithm>
 #include <cmath>
 #include <functional>
-#include <iterator>
 #include <limits>
 #include <vector>
 
@@ -19,6 +19,28 @@ namespace {
 constexpr char SOFT_HYPHEN_UTF8[] = "\xC2\xAD";
 constexpr size_t SOFT_HYPHEN_BYTES = 2;
 
+// Returns the first rendered codepoint of a word (skipping leading soft hyphens).
+uint32_t firstCodepoint(const std::string& word) {
+  const auto* ptr = reinterpret_cast<const unsigned char*>(word.c_str());
+  while (true) {
+    const uint32_t cp = utf8NextCodepoint(&ptr);
+    if (cp == 0) return 0;
+    if (cp != 0x00AD) return cp;  // skip soft hyphens
+  }
+}
+
+// Returns the last codepoint of a word by scanning backward for the start of the last UTF-8 sequence.
+uint32_t lastCodepoint(const std::string& word) {
+  if (word.empty()) return 0;
+  // UTF-8 continuation bytes start with 10xxxxxx; scan backward to find the leading byte.
+  size_t i = word.size() - 1;
+  while (i > 0 && (static_cast<uint8_t>(word[i]) & 0xC0) == 0x80) {
+    --i;
+  }
+  const auto* ptr = reinterpret_cast<const unsigned char*>(word.c_str() + i);
+  return utf8NextCodepoint(&ptr);
+}
+
 bool containsSoftHyphen(const std::string& word) { return word.find(SOFT_HYPHEN_UTF8) != std::string::npos; }
 
 // Removes every soft hyphen in-place so rendered glyphs match measured widths.
@@ -30,7 +52,7 @@ void stripSoftHyphensInPlace(std::string& word) {
 }
 
 // Returns the advance width for a word while ignoring soft hyphen glyphs and optionally appending a visible hyphen.
-// Uses advance width (sum of glyph advances) rather than bounding box width so that italic glyph overhangs
+// Uses advance width (sum of glyph advances + kerning) rather than bounding box width so that italic glyph overhangs
 // don't inflate inter-word spacing.
 uint16_t measureWordWidth(const GfxRenderer& renderer, const int fontId, const std::string& word,
                           const EpdFontFamily::Style style, const bool appendHyphen = false) {
@@ -79,55 +101,53 @@ void ParsedText::layoutAndExtractLines(const GfxRenderer& renderer, const int fo
   applyParagraphIndent();
 
   const int pageWidth = viewportWidth;
-  const int spaceWidth = renderer.getSpaceWidth(fontId);
   auto wordWidths = calculateWordWidths(renderer, fontId);
 
-  // Build indexed continues vector from the parallel list for O(1) access during layout
-  std::vector<bool> continuesVec(wordContinues.begin(), wordContinues.end());
-
   std::vector<size_t> lineBreakIndices;
   if (hyphenationEnabled) {
     // Use greedy layout that can split words mid-loop when a hyphenated prefix fits.
-    lineBreakIndices = computeHyphenatedLineBreaks(renderer, fontId, pageWidth, spaceWidth, wordWidths, continuesVec);
+    lineBreakIndices = computeHyphenatedLineBreaks(renderer, fontId, pageWidth, wordWidths, wordContinues);
   } else {
-    lineBreakIndices = computeLineBreaks(renderer, fontId, pageWidth, spaceWidth, wordWidths, continuesVec);
+    lineBreakIndices = computeLineBreaks(renderer, fontId, pageWidth, wordWidths, wordContinues);
   }
   const size_t lineCount = includeLastLine ? lineBreakIndices.size() : lineBreakIndices.size() - 1;
 
   for (size_t i = 0; i < lineCount; ++i) {
-    extractLine(i, pageWidth, spaceWidth, wordWidths, continuesVec, lineBreakIndices, processLine);
+    extractLine(i, pageWidth, wordWidths, wordContinues, lineBreakIndices, processLine, renderer, fontId);
+  }
+
+  // Remove consumed words so size() reflects only remaining words
+  if (lineCount > 0) {
+    const size_t consumed = lineBreakIndices[lineCount - 1];
+    words.erase(words.begin(), words.begin() + consumed);
+    wordStyles.erase(wordStyles.begin(), wordStyles.begin() + consumed);
+    wordContinues.erase(wordContinues.begin(), wordContinues.begin() + consumed);
   }
 }
 
 std::vector<uint16_t> ParsedText::calculateWordWidths(const GfxRenderer& renderer, const int fontId) {
-  const size_t totalWordCount = words.size();
-
   std::vector<uint16_t> wordWidths;
-  wordWidths.reserve(totalWordCount);
+  wordWidths.reserve(words.size());
 
-  auto wordsIt = words.begin();
-  auto wordStylesIt = wordStyles.begin();
-
-  while (wordsIt != words.end()) {
-    wordWidths.push_back(measureWordWidth(renderer, fontId, *wordsIt, *wordStylesIt));
-
-    std::advance(wordsIt, 1);
-    std::advance(wordStylesIt, 1);
+  for (size_t i = 0; i < words.size(); ++i) {
+    wordWidths.push_back(measureWordWidth(renderer, fontId, words[i], wordStyles[i]));
   }
 
   return wordWidths;
 }
 
 std::vector<size_t> ParsedText::computeLineBreaks(const GfxRenderer& renderer, const int fontId, const int pageWidth,
-                                                  const int spaceWidth, std::vector<uint16_t>& wordWidths,
-                                                  std::vector<bool>& continuesVec) {
+                                                  std::vector<uint16_t>& wordWidths, std::vector<bool>& continuesVec) {
   if (words.empty()) {
     return {};
   }
 
-  // Calculate first line indent (only for left/justified text without extra paragraph spacing)
+  // Calculate first line indent (only for left/justified text).
+  // Positive text-indent (paragraph indent) is suppressed when extraParagraphSpacing is on.
+  // Negative text-indent (hanging indent, e.g. margin-left:3em; text-indent:-1em) always applies —
+  // it is structural (positions the bullet/marker), not decorative.
   const int firstLineIndent =
-      blockStyle.textIndent > 0 && !extraParagraphSpacing &&
+      blockStyle.textIndentDefined && (blockStyle.textIndent < 0 || !extraParagraphSpacing) &&
               (blockStyle.alignment == CssTextAlign::Justify || blockStyle.alignment == CssTextAlign::Left)
           ? blockStyle.textIndent
           : 0;
@@ -137,8 +157,7 @@ std::vector<size_t> ParsedText::computeLineBreaks(const GfxRenderer& renderer, c
     // First word needs to fit in reduced width if there's an indent
     const int effectiveWidth = i == 0 ? pageWidth - firstLineIndent : pageWidth;
     while (wordWidths[i] > effectiveWidth) {
-      if (!hyphenateWordAtIndex(i, effectiveWidth, renderer, fontId, wordWidths, /*allowFallbackBreaks=*/true,
-                                &continuesVec)) {
+      if (!hyphenateWordAtIndex(i, effectiveWidth, renderer, fontId, wordWidths, /*allowFallbackBreaks=*/true)) {
         break;
       }
     }
@@ -164,7 +183,14 @@ std::vector<size_t> ParsedText::computeLineBreaks(const GfxRenderer& renderer, c
 
     for (size_t j = i; j < totalWordCount; ++j) {
       // Add space before word j, unless it's the first word on the line or a continuation
-      const int gap = j > static_cast<size_t>(i) && !continuesVec[j] ? spaceWidth : 0;
+      int gap = 0;
+      if (j > static_cast<size_t>(i) && !continuesVec[j]) {
+        gap =
+            renderer.getSpaceAdvance(fontId, lastCodepoint(words[j - 1]), firstCodepoint(words[j]), wordStyles[j - 1]);
+      } else if (j > static_cast<size_t>(i) && continuesVec[j]) {
+        // Cross-boundary kerning for continuation words (e.g. nonbreaking spaces, attached punctuation)
+        gap = renderer.getKerning(fontId, lastCodepoint(words[j - 1]), firstCodepoint(words[j]), wordStyles[j - 1]);
+      }
       currlen += wordWidths[j] + gap;
 
       if (currlen > effectivePageWidth) {
@@ -246,12 +272,14 @@ void ParsedText::applyParagraphIndent() {
 
 // Builds break indices while opportunistically splitting the word that would overflow the current line.
 std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& renderer, const int fontId,
-                                                            const int pageWidth, const int spaceWidth,
-                                                            std::vector<uint16_t>& wordWidths,
+                                                            const int pageWidth, std::vector<uint16_t>& wordWidths,
                                                             std::vector<bool>& continuesVec) {
-  // Calculate first line indent (only for left/justified text without extra paragraph spacing)
+  // Calculate first line indent (only for left/justified text).
+  // Positive text-indent (paragraph indent) is suppressed when extraParagraphSpacing is on.
+  // Negative text-indent (hanging indent, e.g. margin-left:3em; text-indent:-1em) always applies —
+  // it is structural (positions the bullet/marker), not decorative.
   const int firstLineIndent =
-      blockStyle.textIndent > 0 && !extraParagraphSpacing &&
+      blockStyle.textIndentDefined && (blockStyle.textIndent < 0 || !extraParagraphSpacing) &&
               (blockStyle.alignment == CssTextAlign::Justify || blockStyle.alignment == CssTextAlign::Left)
           ? blockStyle.textIndent
           : 0;
@@ -270,7 +298,15 @@ std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& r
     // Consume as many words as possible for current line, splitting when prefixes fit
     while (currentIndex < wordWidths.size()) {
       const bool isFirstWord = currentIndex == lineStart;
-      const int spacing = isFirstWord || continuesVec[currentIndex] ? 0 : spaceWidth;
+      int spacing = 0;
+      if (!isFirstWord && !continuesVec[currentIndex]) {
+        spacing = renderer.getSpaceAdvance(fontId, lastCodepoint(words[currentIndex - 1]),
+                                           firstCodepoint(words[currentIndex]), wordStyles[currentIndex - 1]);
+      } else if (!isFirstWord && continuesVec[currentIndex]) {
+        // Cross-boundary kerning for continuation words (e.g. nonbreaking spaces, attached punctuation)
+        spacing = renderer.getKerning(fontId, lastCodepoint(words[currentIndex - 1]),
+                                      firstCodepoint(words[currentIndex]), wordStyles[currentIndex - 1]);
+      }
       const int candidateWidth = spacing + wordWidths[currentIndex];
 
       // Word fits on current line
@@ -284,8 +320,8 @@ std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& r
       const int availableWidth = effectivePageWidth - lineWidth - spacing;
       const bool allowFallbackBreaks = isFirstWord;  // Only for first word on line
 
-      if (availableWidth > 0 && hyphenateWordAtIndex(currentIndex, availableWidth, renderer, fontId, wordWidths,
-                                                     allowFallbackBreaks, &continuesVec)) {
+      if (availableWidth > 0 &&
+          hyphenateWordAtIndex(currentIndex, availableWidth, renderer, fontId, wordWidths, allowFallbackBreaks)) {
         // Prefix now fits; append it to this line and move to next line
         lineWidth += spacing + wordWidths[currentIndex];
         ++currentIndex;
@@ -317,20 +353,14 @@ std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& r
 // available width.
 bool ParsedText::hyphenateWordAtIndex(const size_t wordIndex, const int availableWidth, const GfxRenderer& renderer,
                                       const int fontId, std::vector<uint16_t>& wordWidths,
-                                      const bool allowFallbackBreaks, std::vector<bool>* continuesVec) {
+                                      const bool allowFallbackBreaks) {
   // Guard against invalid indices or zero available width before attempting to split.
   if (availableWidth <= 0 || wordIndex >= words.size()) {
     return false;
   }
 
-  // Get iterators to target word and style.
-  auto wordIt = words.begin();
-  auto styleIt = wordStyles.begin();
-  std::advance(wordIt, wordIndex);
-  std::advance(styleIt, wordIndex);
-
-  const std::string& word = *wordIt;
-  const auto style = *styleIt;
+  const std::string& word = words[wordIndex];
+  const auto style = wordStyles[wordIndex];
 
   // Collect candidate breakpoints (byte offsets and hyphen requirements).
   auto breakInfos = Hyphenator::breakOffsets(word, allowFallbackBreaks);
@@ -367,16 +397,14 @@ bool ParsedText::hyphenateWordAtIndex(const size_t wordIndex, const int availabl
 
   // Split the word at the selected breakpoint and append a hyphen if required.
   std::string remainder = word.substr(chosenOffset);
-  wordIt->resize(chosenOffset);
+  words[wordIndex].resize(chosenOffset);
   if (chosenNeedsHyphen) {
-    wordIt->push_back('-');
+    words[wordIndex].push_back('-');
   }
 
   // Insert the remainder word (with matching style and continuation flag) directly after the prefix.
-  auto insertWordIt = std::next(wordIt);
-  auto insertStyleIt = std::next(styleIt);
-  words.insert(insertWordIt, remainder);
-  wordStyles.insert(insertStyleIt, style);
+  words.insert(words.begin() + wordIndex + 1, remainder);
+  wordStyles.insert(wordStyles.begin() + wordIndex + 1, style);
 
   // Continuation flag handling after splitting a word into prefix + remainder.
   //
@@ -397,17 +425,8 @@ bool ParsedText::hyphenateWordAtIndex(const size_t wordIndex, const int availabl
   //
   // This lets the backtracking loop keep the entire prefix group ("200 Quadrat-") on one
   // line, while "kilometer" moves to the next line.
-  auto continuesIt = wordContinues.begin();
-  std::advance(continuesIt, wordIndex);
-  // *continuesIt is intentionally left unchanged — the prefix keeps its original attachment.
-  const auto insertContinuesIt = std::next(continuesIt);
-  wordContinues.insert(insertContinuesIt, false);
-
-  // Keep the indexed vector in sync if provided.
-  if (continuesVec) {
-    // (*continuesVec)[wordIndex] stays unchanged — prefix keeps its attachment.
-    continuesVec->insert(continuesVec->begin() + wordIndex + 1, false);
-  }
+  // wordContinues[wordIndex] is intentionally left unchanged — the prefix keeps its original attachment.
+  wordContinues.insert(wordContinues.begin() + wordIndex + 1, false);
 
   // Update cached widths to reflect the new prefix/remainder pairing.
   wordWidths[wordIndex] = static_cast<uint16_t>(chosenWidth);
@@ -416,87 +435,100 @@ bool ParsedText::hyphenateWordAtIndex(const size_t wordIndex, const int availabl
   return true;
 }
 
-void ParsedText::extractLine(const size_t breakIndex, const int pageWidth, const int spaceWidth,
-                             const std::vector<uint16_t>& wordWidths, const std::vector<bool>& continuesVec,
-                             const std::vector<size_t>& lineBreakIndices,
-                             const std::function<void(std::shared_ptr<TextBlock>)>& processLine) {
+void ParsedText::extractLine(const size_t breakIndex, const int pageWidth, const std::vector<uint16_t>& wordWidths,
+                             const std::vector<bool>& continuesVec, const std::vector<size_t>& lineBreakIndices,
+                             const std::function<void(std::shared_ptr<TextBlock>)>& processLine,
+                             const GfxRenderer& renderer, const int fontId) {
   const size_t lineBreak = lineBreakIndices[breakIndex];
   const size_t lastBreakAt = breakIndex > 0 ? lineBreakIndices[breakIndex - 1] : 0;
   const size_t lineWordCount = lineBreak - lastBreakAt;
 
-  // Calculate first line indent (only for left/justified text without extra paragraph spacing)
+  // Calculate first line indent (only for left/justified text).
+  // Positive text-indent (paragraph indent) is suppressed when extraParagraphSpacing is on.
+  // Negative text-indent (hanging indent, e.g. margin-left:3em; text-indent:-1em) always applies —
+  // it is structural (positions the bullet/marker), not decorative.
   const bool isFirstLine = breakIndex == 0;
   const int firstLineIndent =
-      isFirstLine && blockStyle.textIndent > 0 && !extraParagraphSpacing &&
+      isFirstLine && blockStyle.textIndentDefined && (blockStyle.textIndent < 0 || !extraParagraphSpacing) &&
               (blockStyle.alignment == CssTextAlign::Justify || blockStyle.alignment == CssTextAlign::Left)
           ? blockStyle.textIndent
           : 0;
 
-  // Calculate total word width for this line and count actual word gaps
-  // (continuation words attach to previous word with no gap)
+  // Calculate total word width for this line, count actual word gaps,
+  // and accumulate total natural gap widths (including space kerning adjustments).
   int lineWordWidthSum = 0;
   size_t actualGapCount = 0;
+  int totalNaturalGaps = 0;
 
   for (size_t wordIdx = 0; wordIdx < lineWordCount; wordIdx++) {
     lineWordWidthSum += wordWidths[lastBreakAt + wordIdx];
     // Count gaps: each word after the first creates a gap, unless it's a continuation
     if (wordIdx > 0 && !continuesVec[lastBreakAt + wordIdx]) {
       actualGapCount++;
+      totalNaturalGaps +=
+          renderer.getSpaceAdvance(fontId, lastCodepoint(words[lastBreakAt + wordIdx - 1]),
+                                   firstCodepoint(words[lastBreakAt + wordIdx]), wordStyles[lastBreakAt + wordIdx - 1]);
+    } else if (wordIdx > 0 && continuesVec[lastBreakAt + wordIdx]) {
+      // Cross-boundary kerning for continuation words (e.g. nonbreaking spaces, attached punctuation)
+      totalNaturalGaps +=
+          renderer.getKerning(fontId, lastCodepoint(words[lastBreakAt + wordIdx - 1]),
+                              firstCodepoint(words[lastBreakAt + wordIdx]), wordStyles[lastBreakAt + wordIdx - 1]);
     }
   }
 
   // Calculate spacing (account for indent reducing effective page width on first line)
   const int effectivePageWidth = pageWidth - firstLineIndent;
-  const int spareSpace = effectivePageWidth - lineWordWidthSum;
-
-  int spacing = spaceWidth;
   const bool isLastLine = breakIndex == lineBreakIndices.size() - 1;
 
-  // For justified text, calculate spacing based on actual gap count
-  if (blockStyle.alignment == CssTextAlign::Justify && !isLastLine && actualGapCount >= 1) {
-    spacing = spareSpace / static_cast<int>(actualGapCount);
-  }
+  // For justified text, compute per-gap extra to distribute remaining space evenly
+  const int spareSpace = effectivePageWidth - lineWordWidthSum - totalNaturalGaps;
+  const int justifyExtra = (blockStyle.alignment == CssTextAlign::Justify && !isLastLine && actualGapCount >= 1)
+                               ? spareSpace / static_cast<int>(actualGapCount)
+                               : 0;
 
-  // Calculate initial x position (first line starts at indent for left/justified text)
-  auto xpos = static_cast<uint16_t>(firstLineIndent);
+  // Calculate initial x position (first line starts at indent for left/justified text;
+  // may be negative for hanging indents, e.g. margin-left:3em; text-indent:-1em).
+  auto xpos = static_cast<int16_t>(firstLineIndent);
   if (blockStyle.alignment == CssTextAlign::Right) {
-    xpos = spareSpace - static_cast<int>(actualGapCount) * spaceWidth;
+    xpos = effectivePageWidth - lineWordWidthSum - totalNaturalGaps;
   } else if (blockStyle.alignment == CssTextAlign::Center) {
-    xpos = (spareSpace - static_cast<int>(actualGapCount) * spaceWidth) / 2;
+    xpos = (effectivePageWidth - lineWordWidthSum - totalNaturalGaps) / 2;
   }
 
   // Pre-calculate X positions for words
   // Continuation words attach to the previous word with no space before them
-  std::list<uint16_t> lineXPos;
+  std::vector<int16_t> lineXPos;
+  lineXPos.reserve(lineWordCount);
 
   for (size_t wordIdx = 0; wordIdx < lineWordCount; wordIdx++) {
-    const uint16_t currentWordWidth = wordWidths[lastBreakAt + wordIdx];
-
     lineXPos.push_back(xpos);
 
-    // Add spacing after this word, unless the next word is a continuation
     const bool nextIsContinuation = wordIdx + 1 < lineWordCount && continuesVec[lastBreakAt + wordIdx + 1];
-
-    xpos += currentWordWidth + (nextIsContinuation ? 0 : spacing);
+    if (nextIsContinuation) {
+      int advance = wordWidths[lastBreakAt + wordIdx];
+      // Cross-boundary kerning for continuation words (e.g. nonbreaking spaces, attached punctuation)
+      advance +=
+          renderer.getKerning(fontId, lastCodepoint(words[lastBreakAt + wordIdx]),
+                              firstCodepoint(words[lastBreakAt + wordIdx + 1]), wordStyles[lastBreakAt + wordIdx]);
+      xpos += advance;
+    } else {
+      int gap = 0;
+      if (wordIdx + 1 < lineWordCount) {
+        gap = renderer.getSpaceAdvance(fontId, lastCodepoint(words[lastBreakAt + wordIdx]),
+                                       firstCodepoint(words[lastBreakAt + wordIdx + 1]),
+                                       wordStyles[lastBreakAt + wordIdx]);
+      }
+      if (blockStyle.alignment == CssTextAlign::Justify && !isLastLine) {
+        gap += justifyExtra;
+      }
+      xpos += wordWidths[lastBreakAt + wordIdx] + gap;
+    }
   }
 
-  // Iterators always start at the beginning as we are moving content with splice below
-  auto wordEndIt = words.begin();
-  auto wordStyleEndIt = wordStyles.begin();
-  auto wordContinuesEndIt = wordContinues.begin();
-  std::advance(wordEndIt, lineWordCount);
-  std::advance(wordStyleEndIt, lineWordCount);
-  std::advance(wordContinuesEndIt, lineWordCount);
-
-  // *** CRITICAL STEP: CONSUME DATA USING SPLICE ***
-  std::list<std::string> lineWords;
-  lineWords.splice(lineWords.begin(), words, words.begin(), wordEndIt);
-  std::list<EpdFontFamily::Style> lineWordStyles;
-  lineWordStyles.splice(lineWordStyles.begin(), wordStyles, wordStyles.begin(), wordStyleEndIt);
-
-  // Consume continues flags (not passed to TextBlock, but must be consumed to stay in sync)
-  std::list<bool> lineContinues;
-  lineContinues.splice(lineContinues.begin(), wordContinues, wordContinues.begin(), wordContinuesEndIt);
+  // Build line data by moving from the original vectors using index range
+  std::vector<std::string> lineWords(std::make_move_iterator(words.begin() + lastBreakAt),
+                                     std::make_move_iterator(words.begin() + lineBreak));
+  std::vector<EpdFontFamily::Style> lineWordStyles(wordStyles.begin() + lastBreakAt, wordStyles.begin() + lineBreak);
 
   for (auto& word : lineWords) {
     if (containsSoftHyphen(word)) {

lib/Epub/Epub/ParsedText.h

@@ -3,7 +3,6 @@
 #include <EpdFontFamily.h>
 
 #include <functional>
-#include <list>
 #include <memory>
 #include <string>
 #include <vector>
@@ -14,25 +13,24 @@
 class GfxRenderer;
 
 class ParsedText {
-  std::list<std::string> words;
-  std::list<EpdFontFamily::Style> wordStyles;
-  std::list<bool> wordContinues;  // true = word attaches to previous (no space before it)
+  std::vector<std::string> words;
+  std::vector<EpdFontFamily::Style> wordStyles;
+  std::vector<bool> wordContinues;  // true = word attaches to previous (no space before it)
   BlockStyle blockStyle;
   bool extraParagraphSpacing;
   bool hyphenationEnabled;
 
   void applyParagraphIndent();
-  std::vector<size_t> computeLineBreaks(const GfxRenderer& renderer, int fontId, int pageWidth, int spaceWidth,
+  std::vector<size_t> computeLineBreaks(const GfxRenderer& renderer, int fontId, int pageWidth,
                                         std::vector<uint16_t>& wordWidths, std::vector<bool>& continuesVec);
   std::vector<size_t> computeHyphenatedLineBreaks(const GfxRenderer& renderer, int fontId, int pageWidth,
-                                                  int spaceWidth, std::vector<uint16_t>& wordWidths,
-                                                  std::vector<bool>& continuesVec);
+                                                  std::vector<uint16_t>& wordWidths, std::vector<bool>& continuesVec);
   bool hyphenateWordAtIndex(size_t wordIndex, int availableWidth, const GfxRenderer& renderer, int fontId,
-                            std::vector<uint16_t>& wordWidths, bool allowFallbackBreaks,
-                            std::vector<bool>* continuesVec = nullptr);
-  void extractLine(size_t breakIndex, int pageWidth, int spaceWidth, const std::vector<uint16_t>& wordWidths,
+                            std::vector<uint16_t>& wordWidths, bool allowFallbackBreaks);
+  void extractLine(size_t breakIndex, int pageWidth, const std::vector<uint16_t>& wordWidths,
                    const std::vector<bool>& continuesVec, const std::vector<size_t>& lineBreakIndices,
-                   const std::function<void(std::shared_ptr<TextBlock>)>& processLine);
+                   const std::function<void(std::shared_ptr<TextBlock>)>& processLine, const GfxRenderer& renderer,
+                   int fontId);
   std::vector<uint16_t> calculateWordWidths(const GfxRenderer& renderer, int fontId);
 
  public:

lib/Epub/Epub/Section.cpp

@@ -10,10 +10,10 @@
 #include "parsers/ChapterHtmlSlimParser.h"
 
 namespace {
-constexpr uint8_t SECTION_FILE_VERSION = 13;
+constexpr uint8_t SECTION_FILE_VERSION = 18;
 constexpr uint32_t HEADER_SIZE = sizeof(uint8_t) + sizeof(int) + sizeof(float) + sizeof(bool) + sizeof(uint8_t) +
                                  sizeof(uint16_t) + sizeof(uint16_t) + sizeof(uint16_t) + sizeof(bool) + sizeof(bool) +
-                                 sizeof(uint32_t);
+                                 sizeof(uint8_t) + sizeof(uint32_t) + sizeof(uint32_t);
 }  // namespace
 
 uint32_t Section::onPageComplete(std::unique_ptr<Page> page) {
@@ -36,7 +36,7 @@ uint32_t Section::onPageComplete(std::unique_ptr<Page> page) {
 void Section::writeSectionFileHeader(const int fontId, const float lineCompression, const bool extraParagraphSpacing,
                                      const uint8_t paragraphAlignment, const uint16_t viewportWidth,
                                      const uint16_t viewportHeight, const bool hyphenationEnabled,
-                                     const bool embeddedStyle) {
+                                     const bool embeddedStyle, const uint8_t imageRendering) {
   if (!file) {
     LOG_DBG("SCT", "File not open for writing header");
     return;
@@ -44,7 +44,7 @@ void Section::writeSectionFileHeader(const int fontId, const float lineCompressi
   static_assert(HEADER_SIZE == sizeof(SECTION_FILE_VERSION) + sizeof(fontId) + sizeof(lineCompression) +
                                    sizeof(extraParagraphSpacing) + sizeof(paragraphAlignment) + sizeof(viewportWidth) +
                                    sizeof(viewportHeight) + sizeof(pageCount) + sizeof(hyphenationEnabled) +
-                                   sizeof(embeddedStyle) + sizeof(uint32_t),
+                                   sizeof(embeddedStyle) + sizeof(imageRendering) + sizeof(uint32_t) + sizeof(uint32_t),
                 "Header size mismatch");
   serialization::writePod(file, SECTION_FILE_VERSION);
   serialization::writePod(file, fontId);
@@ -55,13 +55,16 @@ void Section::writeSectionFileHeader(const int fontId, const float lineCompressi
   serialization::writePod(file, viewportHeight);
   serialization::writePod(file, hyphenationEnabled);
   serialization::writePod(file, embeddedStyle);
-  serialization::writePod(file, pageCount);  // Placeholder for page count (will be initially 0 when written)
-  serialization::writePod(file, static_cast<uint32_t>(0));  // Placeholder for LUT offset
+  serialization::writePod(file, imageRendering);
+  serialization::writePod(file, pageCount);  // Placeholder for page count (will be initially 0, patched later)
+  serialization::writePod(file, static_cast<uint32_t>(0));  // Placeholder for LUT offset (patched later)
+  serialization::writePod(file, static_cast<uint32_t>(0));  // Placeholder for anchor map offset (patched later)
 }
 
 bool Section::loadSectionFile(const int fontId, const float lineCompression, const bool extraParagraphSpacing,
                               const uint8_t paragraphAlignment, const uint16_t viewportWidth,
-                              const uint16_t viewportHeight, const bool hyphenationEnabled, const bool embeddedStyle) {
+                              const uint16_t viewportHeight, const bool hyphenationEnabled, const bool embeddedStyle,
+                              const uint8_t imageRendering) {
   if (!Storage.openFileForRead("SCT", filePath, file)) {
     return false;
   }
@@ -84,6 +87,7 @@ bool Section::loadSectionFile(const int fontId, const float lineCompression, con
     uint8_t fileParagraphAlignment;
     bool fileHyphenationEnabled;
     bool fileEmbeddedStyle;
+    uint8_t fileImageRendering;
     serialization::readPod(file, fileFontId);
     serialization::readPod(file, fileLineCompression);
     serialization::readPod(file, fileExtraParagraphSpacing);
@@ -92,11 +96,13 @@ bool Section::loadSectionFile(const int fontId, const float lineCompression, con
     serialization::readPod(file, fileViewportHeight);
     serialization::readPod(file, fileHyphenationEnabled);
     serialization::readPod(file, fileEmbeddedStyle);
+    serialization::readPod(file, fileImageRendering);
 
     if (fontId != fileFontId || lineCompression != fileLineCompression ||
         extraParagraphSpacing != fileExtraParagraphSpacing || paragraphAlignment != fileParagraphAlignment ||
         viewportWidth != fileViewportWidth || viewportHeight != fileViewportHeight ||
-        hyphenationEnabled != fileHyphenationEnabled || embeddedStyle != fileEmbeddedStyle) {
+        hyphenationEnabled != fileHyphenationEnabled || embeddedStyle != fileEmbeddedStyle ||
+        imageRendering != fileImageRendering) {
       file.close();
       LOG_ERR("SCT", "Deserialization failed: Parameters do not match");
       clearCache();
@@ -129,7 +135,7 @@ bool Section::clearCache() const {
 bool Section::createSectionFile(const int fontId, const float lineCompression, const bool extraParagraphSpacing,
                                 const uint8_t paragraphAlignment, const uint16_t viewportWidth,
                                 const uint16_t viewportHeight, const bool hyphenationEnabled, const bool embeddedStyle,
-                                const std::function<void()>& popupFn) {
+                                const uint8_t imageRendering, const std::function<void()>& popupFn) {
   const auto localPath = epub->getSpineItem(spineIndex).href;
   const auto tmpHtmlPath = epub->getCachePath() + "/.tmp_" + std::to_string(spineIndex) + ".html";
 
@@ -179,7 +185,7 @@ bool Section::createSectionFile(const int fontId, const float lineCompression, c
     return false;
   }
   writeSectionFileHeader(fontId, lineCompression, extraParagraphSpacing, paragraphAlignment, viewportWidth,
-                         viewportHeight, hyphenationEnabled, embeddedStyle);
+                         viewportHeight, hyphenationEnabled, embeddedStyle, imageRendering);
   std::vector<uint32_t> lut = {};
 
   // Derive the content base directory and image cache path prefix for the parser
@@ -201,7 +207,7 @@ bool Section::createSectionFile(const int fontId, const float lineCompression, c
       epub, tmpHtmlPath, renderer, fontId, lineCompression, extraParagraphSpacing, paragraphAlignment, viewportWidth,
       viewportHeight, hyphenationEnabled,
       [this, &lut](std::unique_ptr<Page> page) { lut.emplace_back(this->onPageComplete(std::move(page))); },
-      embeddedStyle, contentBase, imageBasePath, popupFn, cssParser);
+      embeddedStyle, contentBase, imageBasePath, imageRendering, popupFn, cssParser);
   Hyphenator::setPreferredLanguage(epub->getLanguage());
   success = visitor.parseAndBuildPages();
 
@@ -234,10 +240,20 @@ bool Section::createSectionFile(const int fontId, const float lineCompression, c
     return false;
   }
 
-  // Go back and write LUT offset
-  file.seek(HEADER_SIZE - sizeof(uint32_t) - sizeof(pageCount));
+  // Write anchor-to-page map for fragment navigation (e.g. footnote targets)
+  const uint32_t anchorMapOffset = file.position();
+  const auto& anchors = visitor.getAnchors();
+  serialization::writePod(file, static_cast<uint16_t>(anchors.size()));
+  for (const auto& [anchor, page] : anchors) {
+    serialization::writeString(file, anchor);
+    serialization::writePod(file, page);
+  }
+
+  // Patch header with final pageCount, lutOffset, and anchorMapOffset
+  file.seek(HEADER_SIZE - sizeof(uint32_t) * 2 - sizeof(pageCount));
   serialization::writePod(file, pageCount);
   serialization::writePod(file, lutOffset);
+  serialization::writePod(file, anchorMapOffset);
   file.close();
   if (cssParser) {
     cssParser->clear();
@@ -250,7 +266,7 @@ std::unique_ptr<Page> Section::loadPageFromSectionFile() {
     return nullptr;
   }
 
-  file.seek(HEADER_SIZE - sizeof(uint32_t));
+  file.seek(HEADER_SIZE - sizeof(uint32_t) * 2);
   uint32_t lutOffset;
   serialization::readPod(file, lutOffset);
   file.seek(lutOffset + sizeof(uint32_t) * currentPage);
@@ -262,3 +278,36 @@ std::unique_ptr<Page> Section::loadPageFromSectionFile() {
   file.close();
   return page;
 }
+
+std::optional<uint16_t> Section::getPageForAnchor(const std::string& anchor) const {
+  FsFile f;
+  if (!Storage.openFileForRead("SCT", filePath, f)) {
+    return std::nullopt;
+  }
+
+  const uint32_t fileSize = f.size();
+  f.seek(HEADER_SIZE - sizeof(uint32_t));
+  uint32_t anchorMapOffset;
+  serialization::readPod(f, anchorMapOffset);
+  if (anchorMapOffset == 0 || anchorMapOffset >= fileSize) {
+    f.close();
+    return std::nullopt;
+  }
+
+  f.seek(anchorMapOffset);
+  uint16_t count;
+  serialization::readPod(f, count);
+  for (uint16_t i = 0; i < count; i++) {
+    std::string key;
+    uint16_t page;
+    serialization::readString(f, key);
+    serialization::readPod(f, page);
+    if (key == anchor) {
+      f.close();
+      return page;
+    }
+  }
+
+  f.close();
+  return std::nullopt;
+}

lib/Epub/Epub/Section.h

@@ -1,6 +1,8 @@
 #pragma once
 #include <functional>
 #include <memory>
+#include <optional>
+#include <string>
 
 #include "Epub.h"
 
@@ -16,7 +18,7 @@ class Section {
 
   void writeSectionFileHeader(int fontId, float lineCompression, bool extraParagraphSpacing, uint8_t paragraphAlignment,
                               uint16_t viewportWidth, uint16_t viewportHeight, bool hyphenationEnabled,
-                              bool embeddedStyle);
+                              bool embeddedStyle, uint8_t imageRendering);
   uint32_t onPageComplete(std::unique_ptr<Page> page);
 
  public:
@@ -30,10 +32,14 @@ class Section {
         filePath(epub->getCachePath() + "/sections/" + std::to_string(spineIndex) + ".bin") {}
   ~Section() = default;
   bool loadSectionFile(int fontId, float lineCompression, bool extraParagraphSpacing, uint8_t paragraphAlignment,
-                       uint16_t viewportWidth, uint16_t viewportHeight, bool hyphenationEnabled, bool embeddedStyle);
+                       uint16_t viewportWidth, uint16_t viewportHeight, bool hyphenationEnabled, bool embeddedStyle,
+                       uint8_t imageRendering);
   bool clearCache() const;
   bool createSectionFile(int fontId, float lineCompression, bool extraParagraphSpacing, uint8_t paragraphAlignment,
                          uint16_t viewportWidth, uint16_t viewportHeight, bool hyphenationEnabled, bool embeddedStyle,
-                         const std::function<void()>& popupFn = nullptr);
+                         uint8_t imageRendering, const std::function<void()>& popupFn = nullptr);
   std::unique_ptr<Page> loadPageFromSectionFile();
+
+  // Look up the page number for an anchor id from the section cache file.
+  std::optional<uint16_t> getPageForAnchor(const std::string& anchor) const;
 };

lib/Epub/Epub/blocks/ImageBlock.cpp

@@ -2,10 +2,9 @@
 
 #include <GfxRenderer.h>
 #include <Logging.h>
-#include <SDCardManager.h>
 #include <Serialization.h>
 
-#include "../converters/DitherUtils.h"
+#include "../converters/DirectPixelWriter.h"
 #include "../converters/ImageDecoderFactory.h"
 
 // Cache file format:
@@ -67,6 +66,9 @@ bool renderFromCache(GfxRenderer& renderer, const std::string& cachePath, int x,
     return false;
   }
 
+  DirectPixelWriter pw;
+  pw.init(renderer);
+
   for (int row = 0; row < cachedHeight; row++) {
     if (cacheFile.read(rowBuffer, bytesPerRow) != bytesPerRow) {
       LOG_ERR("IMG", "Cache read error at row %d", row);
@@ -75,13 +77,14 @@ bool renderFromCache(GfxRenderer& renderer, const std::string& cachePath, int x,
       return false;
     }
 
-    int destY = y + row;
+    const int destY = y + row;
+    pw.beginRow(destY);
     for (int col = 0; col < cachedWidth; col++) {
-      int byteIdx = col / 4;
-      int bitShift = 6 - (col % 4) * 2;  // MSB first within byte
+      const int byteIdx = col >> 2;            // col / 4
+      const int bitShift = 6 - (col & 3) * 2;  // MSB first within byte
       uint8_t pixelValue = (rowBuffer[byteIdx] >> bitShift) & 0x03;
 
-      drawPixelWithRenderMode(renderer, x + col, destY, pixelValue);
+      pw.writePixel(x + col, pixelValue);
     }
   }
 

lib/Epub/Epub/blocks/ImageBlock.h

@@ -1,5 +1,5 @@
 #pragma once
-#include <SdFat.h>
+#include <HalStorage.h>
 
 #include <memory>
 #include <string>

lib/Epub/Epub/blocks/TextBlock.cpp

@@ -12,16 +12,13 @@ void TextBlock::render(const GfxRenderer& renderer, const int fontId, const int
     return;
   }
 
-  auto wordIt = words.begin();
-  auto wordStylesIt = wordStyles.begin();
-  auto wordXposIt = wordXpos.begin();
   for (size_t i = 0; i < words.size(); i++) {
-    const int wordX = *wordXposIt + x;
-    const EpdFontFamily::Style currentStyle = *wordStylesIt;
-    renderer.drawText(fontId, wordX, y, wordIt->c_str(), true, currentStyle);
+    const int wordX = wordXpos[i] + x;
+    const EpdFontFamily::Style currentStyle = wordStyles[i];
+    renderer.drawText(fontId, wordX, y, words[i].c_str(), true, currentStyle);
 
     if ((currentStyle & EpdFontFamily::UNDERLINE) != 0) {
-      const std::string& w = *wordIt;
+      const std::string& w = words[i];
       const int fullWordWidth = renderer.getTextWidth(fontId, w.c_str(), currentStyle);
       // y is the top of the text line; add ascender to reach baseline, then offset 2px below
       const int underlineY = y + renderer.getFontAscenderSize(fontId) + 2;
@@ -41,10 +38,6 @@ void TextBlock::render(const GfxRenderer& renderer, const int fontId, const int
 
       renderer.drawLine(startX, underlineY, startX + underlineWidth, underlineY, true);
     }
-
-    std::advance(wordIt, 1);
-    std::advance(wordStylesIt, 1);
-    std::advance(wordXposIt, 1);
   }
 }
 
@@ -80,15 +73,15 @@ bool TextBlock::serialize(FsFile& file) const {
 
 std::unique_ptr<TextBlock> TextBlock::deserialize(FsFile& file) {
   uint16_t wc;
-  std::list<std::string> words;
-  std::list<uint16_t> wordXpos;
-  std::list<EpdFontFamily::Style> wordStyles;
+  std::vector<std::string> words;
+  std::vector<int16_t> wordXpos;
+  std::vector<EpdFontFamily::Style> wordStyles;
   BlockStyle blockStyle;
 
   // Word count
   serialization::readPod(file, wc);
 
-  // Sanity check: prevent allocation of unreasonably large lists (max 10000 words per block)
+  // Sanity check: prevent allocation of unreasonably large vectors (max 10000 words per block)
   if (wc > 10000) {
     LOG_ERR("TXB", "Deserialization failed: word count %u exceeds maximum", wc);
     return nullptr;

lib/Epub/Epub/blocks/TextBlock.h

@@ -2,9 +2,9 @@
 #include <EpdFontFamily.h>
 #include <HalStorage.h>
 
-#include <list>
 #include <memory>
 #include <string>
+#include <vector>
 
 #include "Block.h"
 #include "BlockStyle.h"
@@ -12,14 +12,14 @@
 // Represents a line of text on a page
 class TextBlock final : public Block {
  private:
-  std::list<std::string> words;
-  std::list<uint16_t> wordXpos;
-  std::list<EpdFontFamily::Style> wordStyles;
+  std::vector<std::string> words;
+  std::vector<int16_t> wordXpos;
+  std::vector<EpdFontFamily::Style> wordStyles;
   BlockStyle blockStyle;
 
  public:
-  explicit TextBlock(std::list<std::string> words, std::list<uint16_t> word_xpos,
-                     std::list<EpdFontFamily::Style> word_styles, const BlockStyle& blockStyle = BlockStyle())
+  explicit TextBlock(std::vector<std::string> words, std::vector<int16_t> word_xpos,
+                     std::vector<EpdFontFamily::Style> word_styles, const BlockStyle& blockStyle = BlockStyle())
       : words(std::move(words)),
         wordXpos(std::move(word_xpos)),
         wordStyles(std::move(word_styles)),
@@ -27,7 +27,9 @@ class TextBlock final : public Block {
   ~TextBlock() override = default;
   void setBlockStyle(const BlockStyle& blockStyle) { this->blockStyle = blockStyle; }
   const BlockStyle& getBlockStyle() const { return blockStyle; }
+  const std::vector<std::string>& getWords() const { return words; }
   bool isEmpty() override { return words.empty(); }
+  size_t wordCount() const { return words.size(); }
   // given a renderer works out where to break the words into lines
   void render(const GfxRenderer& renderer, int fontId, int x, int y) const;
   BlockType getType() override { return TEXT_BLOCK; }

lib/Epub/Epub/converters/DirectPixelWriter.h

@@ -0,0 +1,156 @@
+#pragma once
+
+#include <GfxRenderer.h>
+#include <HalDisplay.h>
+#include <stdint.h>
+
+// Direct framebuffer writer that eliminates per-pixel overhead from the image
+// rendering hot path.  Pre-computes orientation transform as linear coefficients
+// and caches render-mode state so the inner loop is: one multiply, one add,
+// one shift, and one AND per pixel — no branches, no method calls.
+//
+// Caller is responsible for ensuring (outX, outY) are within screen bounds.
+// ImageBlock::render() already validates this before entering the pixel loop,
+// and the JPEG/PNG callbacks pre-clamp destination ranges to screen bounds.
+struct DirectPixelWriter {
+  uint8_t* fb;
+  GfxRenderer::RenderMode mode;
+
+  // Orientation is collapsed into a linear transform:
+  //   phyX = phyXBase + x * phyXStepX + y * phyXStepY
+  //   phyY = phyYBase + x * phyYStepX + y * phyYStepY
+  int phyXBase, phyYBase;
+  int phyXStepX, phyYStepX;  // per logical-X step
+  int phyXStepY, phyYStepY;  // per logical-Y step
+
+  // Row-precomputed: the Y-dependent portion of the physical coords
+  int rowPhyXBase, rowPhyYBase;
+
+  void init(GfxRenderer& renderer) {
+    fb = renderer.getFrameBuffer();
+    mode = renderer.getRenderMode();
+
+    switch (renderer.getOrientation()) {
+      case GfxRenderer::Portrait:
+        // phyX = y, phyY = (DISPLAY_HEIGHT-1) - x
+        phyXBase = 0;
+        phyYBase = HalDisplay::DISPLAY_HEIGHT - 1;
+        phyXStepX = 0;
+        phyYStepX = -1;
+        phyXStepY = 1;
+        phyYStepY = 0;
+        break;
+      case GfxRenderer::LandscapeClockwise:
+        // phyX = (DISPLAY_WIDTH-1) - x, phyY = (DISPLAY_HEIGHT-1) - y
+        phyXBase = HalDisplay::DISPLAY_WIDTH - 1;
+        phyYBase = HalDisplay::DISPLAY_HEIGHT - 1;
+        phyXStepX = -1;
+        phyYStepX = 0;
+        phyXStepY = 0;
+        phyYStepY = -1;
+        break;
+      case GfxRenderer::PortraitInverted:
+        // phyX = (DISPLAY_WIDTH-1) - y, phyY = x
+        phyXBase = HalDisplay::DISPLAY_WIDTH - 1;
+        phyYBase = 0;
+        phyXStepX = 0;
+        phyYStepX = 1;
+        phyXStepY = -1;
+        phyYStepY = 0;
+        break;
+      case GfxRenderer::LandscapeCounterClockwise:
+        // phyX = x, phyY = y
+        phyXBase = 0;
+        phyYBase = 0;
+        phyXStepX = 1;
+        phyYStepX = 0;
+        phyXStepY = 0;
+        phyYStepY = 1;
+        break;
+      default:
+        // Fallback to LandscapeCounterClockwise (identity transform)
+        phyXBase = 0;
+        phyYBase = 0;
+        phyXStepX = 1;
+        phyYStepX = 0;
+        phyXStepY = 0;
+        phyYStepY = 1;
+        break;
+    }
+  }
+
+  // Call once per row before the column loop.
+  // Pre-computes the Y-dependent portion so writePixel() only needs the X part.
+  inline void beginRow(int logicalY) {
+    rowPhyXBase = phyXBase + logicalY * phyXStepY;
+    rowPhyYBase = phyYBase + logicalY * phyYStepY;
+  }
+
+  // Write a single 2-bit dithered pixel value to the framebuffer.
+  // Must be called after beginRow() for the current row.
+  // No bounds checking — caller guarantees coordinates are valid.
+  inline void writePixel(int logicalX, uint8_t pixelValue) const {
+    // Determine whether to draw based on render mode
+    bool draw;
+    bool state;
+    switch (mode) {
+      case GfxRenderer::BW:
+        draw = (pixelValue < 3);
+        state = true;
+        break;
+      case GfxRenderer::GRAYSCALE_MSB:
+        draw = (pixelValue == 1 || pixelValue == 2);
+        state = false;
+        break;
+      case GfxRenderer::GRAYSCALE_LSB:
+        draw = (pixelValue == 1);
+        state = false;
+        break;
+      default:
+        return;
+    }
+
+    if (!draw) return;
+
+    const int phyX = rowPhyXBase + logicalX * phyXStepX;
+    const int phyY = rowPhyYBase + logicalX * phyYStepX;
+
+    const uint16_t byteIndex = phyY * HalDisplay::DISPLAY_WIDTH_BYTES + (phyX >> 3);
+    const uint8_t bitMask = 1 << (7 - (phyX & 7));
+
+    if (state) {
+      fb[byteIndex] &= ~bitMask;  // Clear bit (draw black)
+    } else {
+      fb[byteIndex] |= bitMask;  // Set bit (draw white)
+    }
+  }
+};
+
+// Direct cache writer that eliminates per-pixel overhead from PixelCache::setPixel().
+// Pre-computes row pointer so the inner loop is just byte index + bit manipulation.
+//
+// Caller guarantees coordinates are within cache bounds.
+struct DirectCacheWriter {
+  uint8_t* buffer;
+  int bytesPerRow;
+  int originX;
+  uint8_t* rowPtr;  // Pre-computed for current row
+
+  void init(uint8_t* cacheBuffer, int cacheBytesPerRow, int cacheOriginX) {
+    buffer = cacheBuffer;
+    bytesPerRow = cacheBytesPerRow;
+    originX = cacheOriginX;
+    rowPtr = nullptr;
+  }
+
+  // Call once per row before the column loop.
+  inline void beginRow(int screenY, int cacheOriginY) { rowPtr = buffer + (screenY - cacheOriginY) * bytesPerRow; }
+
+  // Write a 2-bit pixel value. No bounds checking.
+  inline void writePixel(int screenX, uint8_t value) const {
+    const int localX = screenX - originX;
+    const int byteIdx = localX >> 2;            // localX / 4
+    const int bitShift = 6 - (localX & 3) * 2;  // MSB first: pixel 0 at bits 6-7
+    rowPtr[byteIdx] = (rowPtr[byteIdx] & ~(0x03 << bitShift)) | ((value & 0x03) << bitShift);
+  }
+};

lib/Epub/Epub/converters/DitherUtils.h

@@ -1,6 +1,5 @@
 #pragma once
 
-#include <GfxRenderer.h>
 #include <stdint.h>
 
 // 4x4 Bayer matrix for ordered dithering
@@ -26,15 +25,3 @@ inline uint8_t applyBayerDither4Level(uint8_t gray, int x, int y) {
   if (adjusted < 192) return 2;
   return 3;
 }
-
-// Draw a pixel respecting the current render mode for grayscale support
-inline void drawPixelWithRenderMode(GfxRenderer& renderer, int x, int y, uint8_t pixelValue) {
-  GfxRenderer::RenderMode renderMode = renderer.getRenderMode();
-  if (renderMode == GfxRenderer::BW && pixelValue < 3) {
-    renderer.drawPixel(x, y, true);
-  } else if (renderMode == GfxRenderer::GRAYSCALE_MSB && (pixelValue == 1 || pixelValue == 2)) {
-    renderer.drawPixel(x, y, false);
-  } else if (renderMode == GfxRenderer::GRAYSCALE_LSB && pixelValue == 1) {
-    renderer.drawPixel(x, y, false);
-  }
-}

lib/Epub/Epub/converters/ImageToFramebufferDecoder.h

@@ -1,5 +1,5 @@
 #pragma once
-#include <SdFat.h>
+#include <HalStorage.h>
 
 #include <memory>
 #include <string>
@@ -37,4 +37,4 @@ class ImageToFramebufferDecoder {
 
   bool validateImageDimensions(int width, int height, const std::string& format);
   void warnUnsupportedFeature(const std::string& feature, const std::string& imagePath);
-};
+};