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fix: Fix prewarm perf when a page contains many styles (#1451)

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## Summary

**What is the goal of this PR?** (e.g., Implements the new feature for
file uploading.)

Fix prewarm perf when a page contains many styles.

The prewarm page buffer was a single slot, so each `prewarmCache` call
for a new font style freed the previous style's glyphs. On pages with
multiple styles (regular + bold + italic), only the last style was
prewarmed. The others fell through to the hot-group compaction path at
~2-3ms per glyph.

This was most visible on rich formatting (e.g. this [Czech prayer
book](https://stahuj.kancional.cz/e-kniha/kancional.epub) with bold
headings, italic liturgical text, and regular body), where page renders
took 3-5 seconds instead of ~700ms.

Fix: use up to 4 page buffer slots (one per font style) so all styles
stay prewarmed simultaneously.

Fixes #1450.

---

### AI Usage

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please be transparent about their usage as it
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This commit is contained in:
Adrian Wilkins-Caruana
2026-03-22 04:10:41 +11:00
committed by GitHub
parent 53beeeed2b
commit 0c9e8b3ece
2 changed files with 67 additions and 48 deletions
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16
lib/EpdFont/FontDecompressor.h
View File

@@ -9,6 +9,7 @@
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();
@@ -48,16 +49,21 @@ class FontDecompressor {
Stats stats;
InflateReader inflateReader;
// Page buffer: flat array of prewarmed glyph bitmaps with sorted lookup
// 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)
};
uint8_t* pageBuffer = nullptr;
const EpdFontData* pageFont = nullptr;
PageGlyphEntry* pageGlyphs = nullptr;
uint16_t pageGlyphCount = 0;
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.