c1d1e98909
**What is the goal of this PR?** Compress reader font bitmaps to reduce flash usage by 30.7%. **What changes are included?** - New `EpdFontGroup` struct and extended `EpdFontData` with `groups`/`groupCount` fields - `--compress` flag in `fontconvert.py`: groups glyphs (ASCII base group + groups of 8) and compresses each with raw DEFLATE - `FontDecompressor` class with 4-slot LRU cache for on-demand decompression during rendering - `GfxRenderer` transparently routes bitmap access through `getGlyphBitmap()` (compressed or direct flash) - Uses `uzlib` for decompression with minimal heap overhead. - 48 reader fonts (Bookerly, NotoSans 12-18pt, OpenDyslexic) regenerated with compression; 5 UI fonts unchanged - Round-trip verification script (`verify_compression.py`) runs as part of font generation | | baseline | font-compression | Difference | |--|--------|-----------------|------------| | Flash (ELF) | 6,302,476 B (96.2%) | 4,365,022 B (66.6%) | -1,937,454 B (-30.7%) | | firmware.bin | 6,468,192 B | 4,531,008 B | -1,937,184 B (-29.9%) | | RAM | 101,700 B (31.0%) | 103,076 B (31.5%) | +1,376 B (+0.5%) | Comparison of uncompressed baseline vs script-based group compression (4-slot LRU cache, cleared each page). Glyphs are grouped by Unicode block (ASCII, Latin-1, Latin Extended-A, Combining Marks, Cyrillic, General Punctuation, etc.) instead of sequential groups of 8. | | Baseline | Compressed (cold cache) | Difference | |---|---|---|---| | **Median** | 414.9 ms | 431.6 ms | +16.7 ms (+4.0%) | | **Pages** | 37 | 37 | | | | Baseline | Compressed (cold cache) | Difference | |---|---|---|---| | **Heap free (median)** | 187.0 KB | 176.3 KB | -10.7 KB | | **Heap free (min)** | 186.0 KB | 166.5 KB | -19.5 KB | | **Largest block (median)** | 148.0 KB | 128.0 KB | -20.0 KB | | **Largest block (min)** | 148.0 KB | 120.0 KB | -28.0 KB | | | Misses/page | Hit rate | |---|---|---| | **Compressed (cold cache)** | 2.1 | 99.85% | ------ 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**_ Implementation was done by Claude Code (Opus 4.6) based on a plan developed collaboratively. All generated font headers were verified with an automated round-trip decompression test. The firmware was compiled successfully but has not yet been tested on-device. --------- Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
43 lines
1.2 KiB
C++
43 lines
1.2 KiB
C++
#pragma once
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#include <uzlib.h>
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#include <cstdint>
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#include "EpdFontData.h"
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class FontDecompressor {
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public:
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bool init();
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void deinit();
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// Returns pointer to decompressed bitmap data for the given glyph.
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// Valid until LRU eviction (safe for the duration of one glyph render).
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const uint8_t* getBitmap(const EpdFontData* fontData, const EpdGlyph* glyph, uint16_t glyphIndex);
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// Evict all cached decompressed groups (call between pages for within-page-only caching).
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void clearCache();
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private:
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static constexpr uint8_t CACHE_SLOTS = 4;
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struct CacheEntry {
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const EpdFontData* font = nullptr;
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uint16_t groupIndex = 0;
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uint8_t* data = nullptr;
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uint32_t dataSize = 0;
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uint32_t lastUsed = 0;
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bool valid = false;
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};
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struct uzlib_uncomp decomp = {};
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CacheEntry cache[CACHE_SLOTS] = {};
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uint32_t accessCounter = 0;
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void freeAllEntries();
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uint16_t getGroupIndex(const EpdFontData* fontData, uint16_t glyphIndex);
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CacheEntry* findInCache(const EpdFontData* fontData, uint16_t groupIndex);
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CacheEntry* findEvictionCandidate();
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bool decompressGroup(const EpdFontData* fontData, uint16_t groupIndex, CacheEntry* entry);
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};
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