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[GSUB] Merge Ligature and context input matching 

Looks better now...
This commit is contained in:
Behdad Esfahbod 2012-08-28 22:58:55 -04:00
parent 93814ca7dc
commit 191fa885d9
3 changed files with 39 additions and 63 deletions
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4
TODO
View File

@ -1,10 +1,6 @@
General fixes:
=============
- Ligature matching and match_input() of (Chain)Context should use the
same logic. Right now the Ligature logic is more involved. Possibly
merge, or duplicate.
- mask propagation? (when ligation, "or" the masks).
- Warn at compile time (and runtime with HB_DEBUG?) if no Unicode / font

69
src/hb-ot-layout-gsub-table.hh
View File

@ -491,66 +491,21 @@ struct Ligature
unsigned int count = component.len;
if (unlikely (count < 1)) return TRACE_RETURN (false);
hb_apply_context_t::mark_skipping_forward_iterator_t skippy_iter (c, c->buffer->idx, count - 1);
if (skippy_iter.has_no_chance ()) return TRACE_RETURN (false);
unsigned int end_offset;
bool is_mark_ligature;
unsigned int total_component_count;
/*
* This is perhaps the trickiest part of OpenType... Remarks:
*
* - If all components of the ligature were marks, we call this a mark ligature.
*
* - If there is no GDEF, and the ligature is NOT a mark ligature, we categorize
* it as a ligature glyph.
*
* - 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...)
*/
bool is_mark_ligature = !!(c->property & HB_OT_LAYOUT_GLYPH_CLASS_MARK);
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;
if (!skippy_iter.next (&property)) return TRACE_RETURN (false);
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, unless they are attached to the first component itself! */
if (this_lig_id && this_lig_comp && (this_lig_id != first_lig_id))
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]);
}
if (likely (!match_input (c, count,
&component[1],
match_glyph,
NULL,
&end_offset,
&is_mark_ligature,
&total_component_count)))
return TRACE_RETURN (false);
/* Deal, we are forming the ligature. */
c->buffer->merge_clusters (c->buffer->idx, skippy_iter.idx + 1);
c->buffer->merge_clusters (c->buffer->idx, c->buffer->idx + end_offset);
/*
* - If it *is* a mark ligature, we don't allocate a new ligature id, and leave

29
src/hb-ot-layout-gsubgpos-private.hh
View File

@ -421,13 +421,33 @@ static inline bool match_input (hb_apply_context_t *c,
const USHORT input[], /* Array of input values--start with second glyph */
match_func_t match_func,
const void *match_data,
unsigned int *end_offset = NULL)
unsigned int *end_offset = NULL,
bool *p_is_mark_ligature = NULL,
unsigned int *p_total_component_count = NULL)
{
hb_auto_trace_t<HB_DEBUG_APPLY> trace (&c->debug_depth, "APPLY", NULL, HB_FUNC, "idx %d codepoint %u", c->buffer->idx, c->buffer->cur().codepoint);
hb_apply_context_t::mark_skipping_forward_iterator_t skippy_iter (c, c->buffer->idx, count - 1);
if (skippy_iter.has_no_chance ()) return TRACE_RETURN (false);
/*
* This is perhaps the trickiest part of OpenType... Remarks:
*
* - If all components of the ligature were marks, we call this a mark ligature.
*
* - If there is no GDEF, and the ligature is NOT a mark ligature, we categorize
* it as a ligature glyph.
*
* - 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...)
*/
bool is_mark_ligature = !!(c->property & HB_OT_LAYOUT_GLYPH_CLASS_MARK);
unsigned int total_component_count = 0;
@ -443,7 +463,6 @@ static inline bool match_input (hb_apply_context_t *c,
if (!skippy_iter.next (&property)) return TRACE_RETURN (false);
if (likely (!match_func (c->buffer->info[skippy_iter.idx].codepoint, input[i - 1], match_data))) return false;
// 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]);
@ -469,6 +488,12 @@ static inline bool match_input (hb_apply_context_t *c,
if (end_offset)
*end_offset = skippy_iter.idx - c->buffer->idx + 1;
if (p_is_mark_ligature)
*p_is_mark_ligature = is_mark_ligature;
if (p_total_component_count)
*p_total_component_count = total_component_count;
return true;
}