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Avoid OOM during prewarm by loading only ligature data, not kern pairs

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This is particularly important when using SD fonts with many kern pairs
This commit is contained in:
spfenwick
2026-05-02 15:54:40 +12:00
parent 376350c61d
commit 913b7e5f8b
2 changed files with 42 additions and 26 deletions
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lib/EpdFont/SdCardFont.cpp
+39 -24
View File
@@ -66,11 +66,12 @@ void SdCardFont::freeStyleMiniData(PerStyle& s) {
void SdCardFont::freeStyleKernLigatureData(PerStyle& s) {
delete[] s.kernLeftClasses;
s.kernLeftClasses = nullptr;
s.kernClassesLoaded = false;
delete[] s.kernRightClasses;
s.kernRightClasses = nullptr;
delete[] s.ligaturePairs;
s.ligaturePairs = nullptr;
s.kernLigLoaded = false;
s.ligLoaded = false;
}
void SdCardFont::freeStyleMiniKern(PerStyle& s) {
@@ -134,14 +135,17 @@ void SdCardFont::applyKernLigaturePointers(const PerStyle& s, EpdFontData& data)
data.ligaturePairCount = s.header.ligaturePairCount;
}
bool SdCardFont::loadStyleKernLigatureData(PerStyle& s) {
if (s.kernLigLoaded) return true;
bool hasKern = s.header.kernLeftEntryCount > 0;
bool hasLig = s.header.ligaturePairCount > 0;
if (!hasKern && !hasLig) {
s.kernLigLoaded = true;
return true;
}
bool SdCardFont::loadStyleKernLigatureData(PerStyle& s, bool ligatureOnly) {
// During metadata-only (layout) prewarms, skip the kern class tables: the kern
// matrix is never built at layout time so getKerning() returns 0 regardless.
// Skipping them saves ~4KB per style (~17KB total for 4 styles), preventing OOM
// on low-heap devices when long paragraphs try to grow their word vector.
const bool wantKern = !ligatureOnly && s.header.kernLeftEntryCount > 0;
const bool wantLig = s.header.ligaturePairCount > 0;
const bool kernDone = !wantKern || s.kernClassesLoaded;
const bool ligDone = !wantLig || s.ligLoaded;
if (kernDone && ligDone) return true;
FsFile file;
if (!Storage.openFileForRead("SDCF", filePath_, file)) {
@@ -149,7 +153,7 @@ bool SdCardFont::loadStyleKernLigatureData(PerStyle& s) {
return false;
}
if (hasKern) {
if (wantKern && !s.kernClassesLoaded) {
// Load only the small class-lookup tables (~3KB each). The full matrix
// (~36KB contiguous for Literata) is built per-page from SD in
// buildMiniKernMatrix().
@@ -179,9 +183,10 @@ bool SdCardFont::loadStyleKernLigatureData(PerStyle& s) {
file.close();
return false;
}
s.kernClassesLoaded = true;
}
if (hasLig) {
if (wantLig && !s.ligLoaded) {
s.ligaturePairs = new (std::nothrow) EpdLigaturePair[s.header.ligaturePairCount];
if (!s.ligaturePairs) {
LOG_ERR("SDCF", "Failed to allocate ligature pairs");
@@ -202,19 +207,21 @@ bool SdCardFont::loadStyleKernLigatureData(PerStyle& s) {
file.close();
return false;
}
s.ligLoaded = true;
// Make ligatures visible to the stub (used when no mini data built yet).
// Kern stays nullptr on the stub — it is only wired in miniData via
// applyKernLigaturePointers() after buildMiniKernMatrix() runs.
s.stubData.ligaturePairs = s.ligaturePairs;
s.stubData.ligaturePairCount = s.header.ligaturePairCount;
}
file.close();
s.kernLigLoaded = true;
// Make ligatures visible to the stub (used when no mini data built yet).
// Kern stays nullptr on the stub — it is only wired in miniData via
// applyKernLigaturePointers() after buildMiniKernMatrix() runs.
s.stubData.ligaturePairs = s.ligaturePairs;
s.stubData.ligaturePairCount = s.header.ligaturePairCount;
LOG_DBG("SDCF", "Kern classes + lig loaded: kernL=%u, kernR=%u, ligs=%u", s.header.kernLeftEntryCount,
s.header.kernRightEntryCount, s.header.ligaturePairCount);
LOG_DBG("SDCF", "Kern/lig loaded: kernL=%u kernR=%u ligs=%u ligOnly=%d",
s.kernClassesLoaded ? s.header.kernLeftEntryCount : 0u,
s.kernClassesLoaded ? s.header.kernRightEntryCount : 0u,
s.ligLoaded ? s.header.ligaturePairCount : 0u,
ligatureOnly);
return true;
}
@@ -653,7 +660,7 @@ int SdCardFont::prewarm(const char* utf8Text, uint8_t styleMask, bool metadataOn
if (!(styleMask & (1 << si)) || !styles_[si].present) continue;
auto& s = styles_[si];
loadStyleKernLigatureData(s);
loadStyleKernLigatureData(s, /*ligatureOnly=*/true);
if (s.ligaturePairs && s.header.ligaturePairCount > 0) {
for (uint8_t li = 0; li < s.header.ligaturePairCount && cpCount < MAX_PAGE_GLYPHS; li++) {
uint32_t leftCp = s.ligaturePairs[li].pair >> 16;
@@ -1143,7 +1150,7 @@ int SdCardFont::prewarmStyle(uint8_t styleIdx, const uint32_t* codepoints, uint3
kernLigOk = buildMiniKernMatrix(s, codepoints, cpCount);
}
} else if (loadKernLigatureData) {
loadStyleKernLigatureData(s);
loadStyleKernLigatureData(s, /*ligatureOnly=*/true);
// Don't set kernLigOk → mini kern matrix stays null on miniData, but
// ligatures are still resident on stubData (set in loadStyleKernLigatureData).
}
@@ -1161,7 +1168,7 @@ int SdCardFont::prewarmStyle(uint8_t styleIdx, const uint32_t* codepoints, uint3
if (kernLigOk) {
// Full prewarm: wire mini kern matrix + class tables + ligatures.
applyKernLigaturePointers(s, s.miniData);
} else if (loadKernLigatureData && s.kernLigLoaded) {
} else if (loadKernLigatureData && s.ligLoaded) {
// Layout-only prewarm: wire ligatures so applyLigatures() works (e.g. "fi"
// measures correctly). Skip the kern matrix — getKerning() returns 0
// cleanly when kernMatrix is null. Per-pair kern is applied at render time.
@@ -1173,6 +1180,8 @@ int SdCardFont::prewarmStyle(uint8_t styleIdx, const uint32_t* codepoints, uint3
s.epdFont.data = &s.miniData;
s.miniMode = metadataOnly ? PerStyle::MiniMode::METADATA : PerStyle::MiniMode::FULL;
LOG_DBG("SDCF", "prewarmStyle %u: mode→%s glyphs=%u bitmap=%p",
styleIdx, metadataOnly ? "METADATA" : "FULL", validCount, s.miniBitmap);
// Accumulate stats
stats_.sdReadTimeMs += sdTime;
@@ -1236,6 +1245,10 @@ const EpdGlyph* SdCardFont::onGlyphMiss(void* ctx, uint32_t codepoint) {
const auto& s = self->styles_[styleIdx];
if (!s.fullIntervals) return nullptr;
// Diagnostic: log first miss per codepoint+style to show why it bypassed prewarm
LOG_DBG("SDCF", "onGlyphMiss: U+%04X style %u miniMode=%u miniIntervals=%u bitmap=%p",
codepoint, styleIdx, (uint8_t)s.miniMode, s.miniIntervalCount, s.miniBitmap);
// Check overflow cache first (matching both codepoint and style)
for (uint32_t i = 0; i < self->overflowCount_; i++) {
if (self->overflow_[i].codepoint == codepoint && self->overflow_[i].styleIdx == styleIdx) {
@@ -1309,6 +1322,8 @@ const EpdGlyph* SdCardFont::onGlyphMiss(void* ctx, uint32_t codepoint) {
// All reads succeeded — commit to slot (evict old entry if at capacity)
if (wasAtCapacity) {
LOG_DBG("SDCF", "Overflow: evicting U+%04X style %u from slot %u",
self->overflow_[slot].codepoint, self->overflow_[slot].styleIdx, slot);
delete[] self->overflow_[slot].bitmap;
}
self->overflow_[slot].glyph = tempGlyph;
lib/EpdFont/SdCardFont.h
+3 -2
View File
@@ -118,7 +118,8 @@ class SdCardFont {
EpdKernClassEntry* kernLeftClasses = nullptr;
EpdKernClassEntry* kernRightClasses = nullptr;
EpdLigaturePair* ligaturePairs = nullptr;
bool kernLigLoaded = false;
bool ligLoaded = false; ///< ligaturePairs resident
bool kernClassesLoaded = false; ///< kernLeft/RightClasses resident (skipped during metadata-only prewarm)
// Stub EpdFontData returned when not prewarmed
EpdFontData stubData{};
@@ -204,7 +205,7 @@ class SdCardFont {
void freeStyleAll(PerStyle& s);
void freeStyleKernLigatureData(PerStyle& s);
void freeStyleMiniKern(PerStyle& s);
bool loadStyleKernLigatureData(PerStyle& s);
bool loadStyleKernLigatureData(PerStyle& s, bool ligatureOnly = false);
bool buildMiniKernMatrix(PerStyle& s, const uint32_t* codepoints, uint32_t cpCount);
void applyKernLigaturePointers(const PerStyle& s, EpdFontData& data) const;
void applyGlyphMissCallback(uint8_t styleIdx);