On ESP32-C3 with USB CDC, Serial.printf() blocks indefinitely when USB
is not connected. This caused device freezes when booted without USB.
Solution: Call Serial.setTxTimeoutMs(0) after Serial.begin() to make
all Serial output non-blocking.
Also added if (Serial) guards to high-traffic logging paths in
EpubReaderActivity as belt-and-suspenders protection.
Includes documentation of the debugging process and Serial call inventory.
Also applies clang-format to fix pre-existing formatting issues.
- Add global high contrast mode flag in BitmapHelpers
- Modify quantization thresholds for high contrast rendering
- Update ditherer classes (Atkinson, Floyd-Steinberg) for contrast mode
- Add displayContrast setting with persistence
- Add "High Contrast" toggle in display settings
- Apply high contrast mode on startup from saved settings
## Summary
* **What is the goal of this PR?** (e.g., Fixes a bug in the user
authentication module,
Display the book cover image in the **"Continue Reading"** card on the
home screen, with fast navigation using framebuffer caching.
* **What changes are included?**
- Display book cover image in the "Continue Reading" card on home screen
- Load cover from cached BMP (same as sleep screen cover)
- Add framebuffer store/restore functions (`copyStoredBwBuffer`,
`freeStoredBwBuffer`) for fast navigation after initial render
- Fix `drawBitmap` scaling bug: apply scale to offset only, not to base
coordinates
- Add white text boxes behind title/author/continue reading label for
readability on cover
- Support both EPUB and XTC file cover images
- Increase HomeActivity task stack size from 2048 to 4096 for cover
image rendering
## Additional Context
* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks, specific areas to
focus on).
- Performance: First render loads cover from SD card (~800ms),
subsequent navigation uses cached framebuffer (~instant)
- Memory: Framebuffer cache uses ~48KB (6 chunks × 8KB) while on home
screen, freed on exit
- Fallback: If cover image is not available, falls back to standard
text-only display
- The `drawBitmap` fix corrects a bug where screenY = (y + offset) scale
was incorrectly scaling the base coordinates. Now correctly uses screenY
= y + (offset scale)
1. Refactor Bitmap.cpp/h to expose the options for FloydSteinberg and
brightness/gamma correction at runtime
2. Fine-tune the thresholds for Floyd Steiberg and simple quantization
to better match the display's colors
Turns out that 2 is enough to make the images render properly, so the
brightness boost and gamma adjustment doesn't seem necessary currently
(at least for my test image).
