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fix: handle fallbacks for advance table and prewarm (#1929)

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## Summary
- Fixes #1928 by having the prewarm and advance table functions resolve
fallback styles
---

### AI Usage
Did you use AI tools to help write this code?  YES - Codex

---------

Co-authored-by: Uri Tauber <uritaube@gmail.com>
This commit is contained in:
Chun Ming Lee
2026-05-12 22:11:37 +03:00
committed by GitHub
co-authored by Uri Tauber
parent 30a209de8b
commit db3bb850b2
3 changed files with 43 additions and 17 deletions
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lib/EpdFont/SdCardFont.cpp
+35
View File
@@ -9,6 +9,8 @@
#include <cstring>
#include <memory>
#include "EpdFontFamily.h"
static_assert(sizeof(EpdGlyph) == 16, "EpdGlyph must be 16 bytes to match .cpfont file layout");
static_assert(sizeof(EpdUnicodeInterval) == 12, "EpdUnicodeInterval must be 12 bytes to match .cpfont file layout");
static_assert(sizeof(EpdKernClassEntry) == 3, "EpdKernClassEntry must be 3 bytes to match .cpfont file layout");
@@ -587,6 +589,8 @@ int32_t SdCardFont::findGlobalGlyphIndex(const PerStyle& s, uint32_t codepoint)
int SdCardFont::prewarm(const char* utf8Text, uint8_t styleMask, bool metadataOnly) {
if (!loaded_) return -1;
styleMask = resolveStyleMask(styleMask);
if (styleMask == 0) return 0;
unsigned long startMs = millis();
@@ -1017,6 +1021,8 @@ uint16_t SdCardFont::getAdvance(uint32_t codepoint, uint8_t style) const {
int SdCardFont::buildAdvanceTable(const char* utf8Text, uint8_t styleMask) {
if (!loaded_) return -1;
styleMask = resolveStyleMask(styleMask);
if (styleMask == 0) return 0;
// Note: advance table is preserved across calls. We only fetch codepoints
// not already present, then merge them in. Use clearPersistentCache() to
@@ -1194,6 +1200,35 @@ EpdFont* SdCardFont::getEpdFont(uint8_t style) {
bool SdCardFont::hasStyle(uint8_t style) const { return styles_[style & (MAX_STYLES - 1)].present; }
uint8_t SdCardFont::resolveStyle(uint8_t style) const {
static const uint8_t kFallbacks[MAX_STYLES][MAX_STYLES] = {
// REGULAR: REGULAR -> BOLD -> ITALIC -> BOLD_ITALIC
{EpdFontFamily::REGULAR, EpdFontFamily::BOLD, EpdFontFamily::ITALIC, EpdFontFamily::BOLD_ITALIC},
// BOLD: BOLD -> REGULAR -> BOLD_ITALIC -> ITALIC
{EpdFontFamily::BOLD, EpdFontFamily::REGULAR, EpdFontFamily::BOLD_ITALIC, EpdFontFamily::ITALIC},
// ITALIC: ITALIC -> REGULAR -> BOLD_ITALIC -> BOLD
{EpdFontFamily::ITALIC, EpdFontFamily::REGULAR, EpdFontFamily::BOLD_ITALIC, EpdFontFamily::BOLD},
// BOLD_ITALIC: BOLD_ITALIC -> BOLD -> ITALIC -> REGULAR
{EpdFontFamily::BOLD_ITALIC, EpdFontFamily::BOLD, EpdFontFamily::ITALIC, EpdFontFamily::REGULAR},
};
const uint8_t styleBits = style & (MAX_STYLES - 1);
for (uint8_t candidate : kFallbacks[styleBits]) {
if (styles_[candidate].present) return candidate;
}
return EpdFontFamily::REGULAR;
}
uint8_t SdCardFont::resolveStyleMask(uint8_t styleMask) const {
uint8_t resolvedMask = 0;
for (uint8_t si = 0; si < MAX_STYLES; si++) {
if (styleMask & (1 << si)) {
resolvedMask |= static_cast<uint8_t>(1u << resolveStyle(si));
}
}
return resolvedMask;
}
// --- On-demand glyph loading (overflow buffer) ---
const EpdGlyph* SdCardFont::onGlyphMiss(void* ctx, uint32_t codepoint) {