fix(text): single source of truth for glyph advances (#479) - #480
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TestADR054_ShearVariableFont_BoldVsRegular failed locally with GPU CoverageFiller (SparseStrips) because at 40px, AA fringe pixels dominate glyph body — pixel count comparison inverts for bold vs regular. Root cause: SparseStrips (4×4 tiles) and AnalyticFiller (scanline) produce different sub-pixel coverage at small sizes. NOT a gvar bug — variations applied correctly (verified via TextPath coordinate comparison). Fix: increase to 80px where glyph body dominates over AA fringe. Both rasterizers now produce bold > regular consistently.
Introduce advanceResolver — unified advance resolution used by Advance(), Glyphs(), and AppendGlyphs(). Priority: TT hinted > HVAR > raw hmtx. This matches drawGlyphs' hintedOrRawAdvance() ensuring MeasureString and DrawString agree on character positions (Skia/Chrome pattern). Enterprise research: Skia, FreeType, Chrome all enforce measurement == rendering advances from a single source controlled by hinting level. Fixes #479
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Summary
Enterprise research
Skia, FreeType, Chrome all enforce: measurement == rendering advances.
Fixes #479