kc3-lang/freetype

2025-07-04T19:52:53

[sfnt] Rewrite GPOS kerning support. (2/2) The previous code had a fundamental flaw: it didn't validate the necessary parts of the 'GPOS' table before accessing it, causing crashes with malformed data (since `TT_CONFIG_OPTION_GPOS_KERNING` is off by default, standard fuzzers don't catch these problems). Additionally, it did a lot of parsing while accessing kerning data, making it rather slow. The new implementation fixes this. After validation, offsets to the 'GPOS' lookup subtables used in the 'kern' feature that correspond to 'simple' kerning (i.e., similar to 'kern' table kerning) are stored in `TT_Face`; this greatly simplifies and accelerates access to the kerning data. Testing with font `SF-Pro.ttf` version '1.00', the validation time for the 'GPOS' table increases the start-up time of `FT_New_Face` by less than 1%, while calls to `FT_Get_Kerning` become about 3.5 times faster. * include/freetype/internal (gpos_kerning_available): Replace with... (gpos_lookups_kerning, num_gpos_lookups_kerning): ... these new fields. Update callers. * src/ttgpos.c [TT_CONFIG_OPTION_GPOS_KERNING]: A new implementation.