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[GSUB] Don't ligate glyphs attached to different components of ligatures 

This concludes the mark-attachment vs ligating interaction fixes (for now).
This commit is contained in:
Behdad Esfahbod 2012-07-30 00:51:47 -04:00
parent 4751dec8be
commit d1d69ec52e
1 changed files with 24 additions and 0 deletions
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24
src/hb-ot-layout-gsub-table.hh
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@ -518,6 +518,11 @@ struct Ligature
*
* This in fact happened to a font... See:
* https://bugzilla.gnome.org/show_bug.cgi?id=437633
*
* - Ligatures cannot be formed across glyphs attached to different components
* of previous ligatures. Eg. the sequence is LAM,SHADDA,LAM,FATHA,HEH, and
* LAM,LAM,HEH form a ligature, leaving SHADDA,FATHA next to eachother.
* However, it would be wrong to ligate that SHADDA,FATHA sequence.
*/
bool is_mark_ligature = !!(c->property & HB_OT_LAYOUT_GLYPH_CLASS_MARK);
@ -525,6 +530,9 @@ struct Ligature
unsigned int total_component_count = 0;
total_component_count += get_lig_num_comps (c->buffer->cur());
unsigned int first_lig_id = get_lig_id (c->buffer->cur());
unsigned int first_lig_comp = get_lig_comp (c->buffer->cur());
for (unsigned int i = 1; i < count; i++)
{
unsigned int property;
@ -533,6 +541,22 @@ struct Ligature
if (likely (c->buffer->info[skippy_iter.idx].codepoint != component[i])) return TRACE_RETURN (false);
unsigned int this_lig_id = get_lig_id (c->buffer->info[skippy_iter.idx]);
unsigned int this_lig_comp = get_lig_comp (c->buffer->info[skippy_iter.idx]);
if (first_lig_id && first_lig_comp) {
/* If first component was attached to a previous ligature component,
* all subsequent components should be attached to the same ligature
* component, otherwise we shouldn't ligate them. */
if (first_lig_id != this_lig_id || first_lig_comp != this_lig_comp)
return TRACE_RETURN (false);
} else {
/* If first component was NOT attached to a previous ligature component,
* all subsequent components should also NOT be attached to any ligature
* component, otherwise we shouldn't ligate them. */
if (this_lig_id && this_lig_comp)
return TRACE_RETURN (false);
}
is_mark_ligature = is_mark_ligature && (property & HB_OT_LAYOUT_GLYPH_CLASS_MARK);
total_component_count += get_lig_num_comps (c->buffer->info[skippy_iter.idx]);
}