cottongin/crosspoint-reader-mod
1
1
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

perf: Improve font drawing performance (#978)

Browse Source 
## Summary

* ``renderChar`` checked ``is2Bit`` on every pixel inside the inner
loop, even though the value is constant for the lifetime of a single
glyph
* Moved the branch above both loops so each path (2-bit antialiased /
1-bit monochrome) runs without a per-pixel conditional
* Eliminates redundant work in the two inner loops that render font
glyphs to the frame buffer, targeting ``renderChar`` and
``drawTextRotated90CW`` in ``GfxRenderer.cpp``

## Additional Context
* Measured on device using a dedicated framebuffer benchmark (no display
refresh). 100 repetitions of "The quick brown fox jumps".

| Test            | Before          | After           | Change  |
|-----------------|-----------------|-----------------|---------|
| drawText UI12   | 1,337 µs/call | 1,024 µs/call | −23%|
| drawText Bookerly14 | 2.174 µs / call | 1,847 µs/call | −15% |

---

### 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? _**PARTIALLY**_ Claude did
the analysis and wrote the benchmarks
This commit is contained in:
jpirnay
2026-02-20 01:12:05 +01:00
committed by GitHub
parent 63b2643534
commit 07d715e32d
2 changed files with 117 additions and 130 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
lib/GfxRenderer/GfxRenderer.h
View File

@@ -38,10 +38,9 @@ class GfxRenderer {
uint8_t* bwBufferChunks[BW_BUFFER_NUM_CHUNKS] = {nullptr};
std::map<int, EpdFontFamily> fontMap;
FontDecompressor* fontDecompressor = nullptr;
void renderChar(const EpdFontFamily& fontFamily, uint32_t cp, int* x, const int* y, bool pixelState,
void renderChar(const EpdFontFamily& fontFamily, uint32_t cp, int* x, int* y, bool pixelState,
EpdFontFamily::Style style) const;
void freeBwBufferChunks();
const uint8_t* getGlyphBitmap(const EpdFontData* fontData, const EpdGlyph* glyph) const;
template <Color color>
void drawPixelDither(int x, int y) const;
template <Color color>
@@ -132,6 +131,9 @@ class GfxRenderer {
void restoreBwBuffer(); // Restore and free the stored buffer
void cleanupGrayscaleWithFrameBuffer() const;
// Font helpers
const uint8_t* getGlyphBitmap(const EpdFontData* fontData, const EpdGlyph* glyph) const;
// Low level functions
uint8_t* getFrameBuffer() const;
static size_t getBufferSize();