## Problem
Custom sleep wallpapers feel repetitive — the same image appearing
multiple times in a short session. Only the single most-recently-shown
index was stored (`uint8_t lastSleepImage`), so on collections of 3–5
images, two-pick cycles were common. On larger collections, any image
could reappear within the next few picks.
## Solution
Add a 16-entry circular recency buffer to `CrossPointState` that
excludes recently shown wallpapers from selection.
**Recency buffer** (`recentSleepImages[16]`, `recentSleepPos`,
`recentSleepFill` — 34 bytes DRAM):
- Tracks the last 16 shown wallpaper indices
- On each pick, rerolls up to 20 times if the candidate was recently
shown
- Window auto-shrinks to `numFiles - 1` for small collections
(guarantees a non-repeat is always possible)
- `isRecentSleep()` clamps to `recentSleepFill` to avoid false positives
on unwritten buffer slots
- State persisted to `state.json` so the buffer survives sleep/wake
cycles
**Migration**:
- Binary (`state.bin`): old `lastSleepImage` field seeded into the new
buffer if valid
- JSON (`state.json`): legacy `lastSleepImage` key detected and seeded
into the buffer when upgrading from older firmware
## Index type fix
`randomFileIndex` upgraded from `uint8_t` to `uint16_t` — silently
truncated for collections larger than 255 wallpapers.
## Repeat probability: before vs after
Chance of seeing a recently-shown image on the next pick. After:
`(numFiles - 16) / numFiles` once collection exceeds the window; 0%
while ≤17.
| Collection | Before | After |
|---|---|---|
| 3 | 50% | 0% |
| 5 | 75% | 0% |
| 10 | 89% | 0% |
| 17 | 94% | 0% |
| 18 | 94% | 6% |
| 20 | 95% | 20% |
| 25 | 96% | 36% |
| 30 | 97% | 47% |
| 50 | 98% | 68% |
| 100 | 99% | 84% |
## Memory impact
| Addition | Size |
|---|---|
| `recentSleepImages[16]` | 32 bytes DRAM |
| `recentSleepPos` + `recentSleepFill` | 2 bytes DRAM |
| **Total** | **34 bytes DRAM** |
## Files changed
- `src/CrossPointState.h` — recency buffer fields + `isRecentSleep()` /
`pushRecentSleep()` declarations
- `src/CrossPointState.cpp` — `isRecentSleep()` / `pushRecentSleep()`
implementations + binary migration path
- `src/JsonSettingsIO.cpp` — JSON serialisation of buffer state + JSON
migration
- `src/activities/boot_sleep/SleepActivity.cpp` — retry loop with
recency check
Co-authored-by: Patryk Radtke <patryk@Patryks-MacBook-Pro.local>
## Summary
* **What is the goal of this PR?** fix edge case for definition
## Additional Context
If loadFromFile() returns false (no state file exists — first boot, or
SD missing), lastSleepImage is never set and contains garbage.
[SleepActivity.cpp:83] then uses it in a while comparison to avoid
repeating the same image. The JSON path (doc["lastSleepImage"] |
(uint8_t)0) handles it, but only if the file exists.
---
### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _** NO **_
## Summary
* This PR introduces a migration from binary file storage to JSON-based
storage for application settings, state, and various credential stores.
This improves readability, maintainability, and allows for easier manual
configuration editing.
* Benefits:
- Settings files are now JSON and can be easily read/edited manually
- Easier to inspect application state and settings during development
- JSON structure is more flexible for future changes
* Drawback: around 15k of additional flash usage
* Compatibility: Seamless migration preserves existing user data
## Additional Context
1. New JSON I/O Infrastructure files:
- JsonSettingsIO: Core JSON serialization/deserialization logic using
ArduinoJson library
- ObfuscationUtils: XOR-based password obfuscation for sensitive data
2. Migrated Components (now use JSON storage with automatic binary
migration):
- CrossPointSettings (settings.json): Main application settings
- CrossPointState (state.json): Application state (open book, sleep
mode, etc.)
- WifiCredentialStore (wifi.json): WiFi network credentials (Password
Obfuscation: Sensitive data like WiFi passwords, uses XOR encryption
with fixed keys. Note: This is obfuscation, not cryptographic security -
passwords can be recovered with the key)
- KOReaderCredentialStore (koreader.json): KOReader sync credentials
- RecentBooksStore (recent.json): Recently opened books list
3. Migration Logic
- Forward Compatibility: New installations use JSON format
- Backward Compatibility: Existing binary files are automatically
migrated to JSON on first load
- Backup Safety: Original binary files are renamed with .bak extension
after successful migration
- Fallback Handling: If JSON parsing fails, system falls back to binary
loading
4. Infrastructure Updates
- HalStorage: Added rename() method for backup operations
---
### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _** YES**_
---------
Co-authored-by: Dave Allie <dave@daveallie.com>
## Summary
* **What is the goal of this PR?** (e.g., Implements the new feature for
file uploading.)
- Allows back button to be held to escape boot loops when reader
activity crashes and device attempts to boot to previous state
- Reduces the need of removing SD card and access to another device to
delete the `/.crosspoint/state.bin`
* **What changes are included?**
- Back button can be held while booting to boot to home screen
- Update of User Guide section to include this feature
## Additional Context
* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks,
specific areas to focus on).
---
### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _**NO**_
---------
Co-authored-by: Arthur Tazhitdinov <lisnake@gmail.com>
When picking a random sleep image from a set of custom images, compare
the randomly chosen index against a cached value in settings. If the
value matches, use the next image (rolling over if it's the last image).
Cache the chosen image index to settings in either case.
## Summary
Implements a tweak on the custom sleep image feature that ensures that
the user gets a new image every time the device goes to sleep.
This change adds a new setting (perhaps there's a better place to cache
this?) that stores the most recently used file index. During picking the
random image index, we compare this against the random index and choose
the next one (modulo the number of image files) if it matches, ensuring
we get a new image.
## Additional Context
As mentioned, I used settings to cache this value since it is a
persisted store, perhaps that's overkill. Open to suggestions on if
there's a better way.
## Summary
* This PR drastically reshapes the structure of the codebase, moving
from the concept of "Screens" to "Activities", restructing the files and
setting up the concept of subactivities.
* This should help with keep the main file clean and containing all
functional logic in the relevant activity.
* CrossPointState is now also a global singleton which should help with
accessing it from within activities.
## Additional Context
* This is probably going to be a bit disruptive for people with open
PRs, sorry 😞
