Harfuzz is requesting kerning between ligature glyph and 0xFFFF(AAT::DELETED_GLYPH) for ttc font in mac

[behdad]

Discussed in #4597

^{Originally posted by DeependraKhetwal February 23, 2024}
Hello we am using harfbuzz with our custom font fuction for getting glyph kerning ( hb_font_get_glyph_h_kerning_func_t) . On mac while we are applying ligatures (for example ff) with lucida grande font (attached) then harfuzz is calling our custom font function for kerning between ligature (gid: 1277) and gid:0xFFFF(AAT::DELETED_GLYPH) . It seems harfuzz is not removing the deleted glyphs in https://github.com/harfbuzz/harfbuzz/blob/main/src/hb-ot-shape.cc#L956 ( because c->plan->apply_gpos is false) before calling the custom kerning function during hb_ot_position. This is resulting in exception as the font function is not able to process the gid:0xFFFF(AAT::DELETED_GLYPH).