diff --git a/src/hb-ot-layout-gsubgpos-private.hh b/src/hb-ot-layout-gsubgpos-private.hh index 472628a39..f2ad9f1c9 100644 --- a/src/hb-ot-layout-gsubgpos-private.hh +++ b/src/hb-ot-layout-gsubgpos-private.hh @@ -374,6 +374,13 @@ struct hb_apply_context_t : inline void reject (void) { num_items++; match_glyph_data--; } + inline matcher_t::may_skip_t + may_skip (const hb_apply_context_t *c, + const hb_glyph_info_t &info) const + { + return matcher.may_skip (c, info); + } + inline bool next (void) { assert (num_items > 0); @@ -736,11 +743,17 @@ static inline bool match_input (hb_apply_context_t *c, * - 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.o - * There is an exception to this: If a ligature tries ligating with marks that - * belong to it itself, go ahead, assuming that the font designer knows what - * they are doing (otherwise it can break Indic stuff when a matra wants to - * ligate with a conjunct...) + * However, it would be wrong to ligate that SHADDA,FATHA sequence. + * There are a couple of exceptions to this: + * + * o If a ligature tries ligating with marks that belong to it itself, go ahead, + * assuming that the font designer knows what they are doing (otherwise it can + * break Indic stuff when a matra wants to ligate with a conjunct, + * + * o If two marks want to ligate and they belong to different components of the + * same ligature glyph, and said ligature glyph is to be ignored according to + * mark-filtering rules, then allow. + * https://github.com/behdad/harfbuzz/issues/545 */ bool is_mark_ligature = _hb_glyph_info_is_mark (&buffer->cur()); @@ -761,13 +774,41 @@ static inline bool match_input (hb_apply_context_t *c, unsigned int this_lig_id = _hb_glyph_info_get_lig_id (&buffer->info[skippy_iter.idx]); unsigned int this_lig_comp = _hb_glyph_info_get_lig_comp (&buffer->info[skippy_iter.idx]); - if (first_lig_id && first_lig_comp) { + 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. */ + * component, otherwise we shouldn't ligate them... */ if (first_lig_id != this_lig_id || first_lig_comp != this_lig_comp) - return_trace (false); - } else { + { + if (first_lig_id != this_lig_id && this_lig_id != 0) + return_trace (false); + + /* ...unless, we are attached to a base ligature and that base + * ligature is ignorable. */ + bool found = false; + const hb_glyph_info_t *out = buffer->out_info; + unsigned int j = buffer->out_len; + while (j && _hb_glyph_info_get_lig_id (&out[j - 1]) == first_lig_id) + { + if (_hb_glyph_info_get_lig_comp (&out[j - 1]) == 0) + { + j--; + found = true; + break; + } + j--; + } + + if (!found) + return_trace (false); + + if (skippy_iter.may_skip (c, out[j]) != hb_apply_context_t::matcher_t::SKIP_YES) + return_trace (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, unless they are attached to the first component itself! */ diff --git a/test/shaping/fonts/sha1sum/a6c76d1bafde4a0b1026ebcc932d2e5c6fd02442.ttf b/test/shaping/fonts/sha1sum/a6c76d1bafde4a0b1026ebcc932d2e5c6fd02442.ttf new file mode 100644 index 000000000..7930a96b0 Binary files /dev/null and b/test/shaping/fonts/sha1sum/a6c76d1bafde4a0b1026ebcc932d2e5c6fd02442.ttf differ diff --git a/test/shaping/tests/ligature-id.tests b/test/shaping/tests/ligature-id.tests index a1ce2bbfe..cd7f16594 100644 --- a/test/shaping/tests/ligature-id.tests +++ b/test/shaping/tests/ligature-id.tests @@ -33,3 +33,4 @@ fonts/sha1sum/1c2fb74c1b2aa173262734c1f616148f1648cfd6.ttf::U+0995,U+09CD,U+0995 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