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[GSUB] Move ligation logic over

This commit is contained in:
Behdad Esfahbod 2012-08-28 23:18:22 -04:00
parent 191fa885d9
commit a177d027d1
2 changed files with 89 additions and 69 deletions
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78
src/hb-ot-layout-gsub-table.hh
View File

@ -507,75 +507,15 @@ struct Ligature
/* Deal, we are forming the ligature. */
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
* the ligature to keep its old ligature id. This will allow it to attach to
* a base ligature in GPOS. Eg. if the sequence is: LAM,LAM,SHADDA,FATHA,HEH,
* and LAM,LAM,HEH for a ligature, they will leave SHADDA and FATHA wit a
* ligature id and component value of 2. Then if SHADDA,FATHA form a ligature
* later, we don't want them to lose their ligature id/component, otherwise
* GPOS will fail to correctly position the mark ligature on top of the
* LAM,LAM,HEH ligature. See:
* https://bugzilla.gnome.org/show_bug.cgi?id=676343
*
* - If a ligature is formed of components that some of which are also ligatures
* themselves, and those ligature components had marks attached to *their*
* components, we have to attach the marks to the new ligature component
* positions! Now *that*'s tricky! And these marks may be following the
* last component of the whole sequence, so we should loop forward looking
* for them and update them.
*
* Eg. the sequence is LAM,LAM,SHADDA,FATHA,HEH, and the font first forms a
* 'calt' ligature of LAM,HEH, leaving the SHADDA and FATHA with a ligature
* id and component == 1. Now, during 'liga', the LAM and the LAM-HEH ligature
* form a LAM-LAM-HEH ligature. We need to reassign the SHADDA and FATHA to
* the new ligature with a component value of 2.
*
* This in fact happened to a font... See:
* https://bugzilla.gnome.org/show_bug.cgi?id=437633
*/
unsigned int klass = is_mark_ligature ? 0 : HB_OT_LAYOUT_GLYPH_CLASS_LIGATURE;
unsigned int lig_id = is_mark_ligature ? 0 : allocate_lig_id (c->buffer);
unsigned int last_lig_id = get_lig_id (c->buffer->cur());
unsigned int last_num_components = get_lig_num_comps (c->buffer->cur());
unsigned int components_so_far = last_num_components;
if (!is_mark_ligature)
set_lig_props_for_ligature (c->buffer->cur(), lig_id, total_component_count);
c->replace_glyph (ligGlyph, klass);
for (unsigned int i = 1; i < count; i++)
{
while (c->should_mark_skip_current_glyph ())
{
if (!is_mark_ligature) {
unsigned int new_lig_comp = components_so_far - last_num_components +
MIN (MAX (get_lig_comp (c->buffer->cur()), 1u), last_num_components);
set_lig_props_for_mark (c->buffer->cur(), lig_id, new_lig_comp);
}
c->buffer->next_glyph ();
}
last_lig_id = get_lig_id (c->buffer->cur());
last_num_components = get_lig_num_comps (c->buffer->cur());
components_so_far += last_num_components;
/* Skip the base glyph */
c->buffer->idx++;
}
if (!is_mark_ligature && last_lig_id) {
/* Re-adjust components for any marks following. */
for (unsigned int i = c->buffer->idx; i < c->buffer->len; i++) {
if (last_lig_id == get_lig_id (c->buffer->info[i])) {
unsigned int new_lig_comp = components_so_far - last_num_components +
MIN (MAX (get_lig_comp (c->buffer->info[i]), 1u), last_num_components);
set_lig_props_for_mark (c->buffer->info[i], lig_id, new_lig_comp);
} else
break;
}
}
ligate_input (c,
count,
&component[1],
ligGlyph,
match_glyph,
NULL,
end_offset,
is_mark_ligature,
total_component_count);
return TRACE_RETURN (true);
}

80
src/hb-ot-layout-gsubgpos-private.hh
View File

@ -496,6 +496,86 @@ static inline bool match_input (hb_apply_context_t *c,
return true;
}
static inline void ligate_input (hb_apply_context_t *c,
unsigned int count, /* Including the first glyph (not matched) */
const USHORT input[], /* Array of input values--start with second glyph */
hb_codepoint_t lig_glyph,
match_func_t match_func,
const void *match_data,
unsigned int end_offset,
bool is_mark_ligature,
unsigned int total_component_count)
{
/*
* - If it *is* a mark ligature, we don't allocate a new ligature id, and leave
* the ligature to keep its old ligature id. This will allow it to attach to
* a base ligature in GPOS. Eg. if the sequence is: LAM,LAM,SHADDA,FATHA,HEH,
* and LAM,LAM,HEH for a ligature, they will leave SHADDA and FATHA wit a
* ligature id and component value of 2. Then if SHADDA,FATHA form a ligature
* later, we don't want them to lose their ligature id/component, otherwise
* GPOS will fail to correctly position the mark ligature on top of the
* LAM,LAM,HEH ligature. See:
* https://bugzilla.gnome.org/show_bug.cgi?id=676343
*
* - If a ligature is formed of components that some of which are also ligatures
* themselves, and those ligature components had marks attached to *their*
* components, we have to attach the marks to the new ligature component
* positions! Now *that*'s tricky! And these marks may be following the
* last component of the whole sequence, so we should loop forward looking
* for them and update them.
*
* Eg. the sequence is LAM,LAM,SHADDA,FATHA,HEH, and the font first forms a
* 'calt' ligature of LAM,HEH, leaving the SHADDA and FATHA with a ligature
* id and component == 1. Now, during 'liga', the LAM and the LAM-HEH ligature
* form a LAM-LAM-HEH ligature. We need to reassign the SHADDA and FATHA to
* the new ligature with a component value of 2.
*
* This in fact happened to a font... See:
* https://bugzilla.gnome.org/show_bug.cgi?id=437633
*/
unsigned int klass = is_mark_ligature ? 0 : HB_OT_LAYOUT_GLYPH_CLASS_LIGATURE;
unsigned int lig_id = is_mark_ligature ? 0 : allocate_lig_id (c->buffer);
unsigned int last_lig_id = get_lig_id (c->buffer->cur());
unsigned int last_num_components = get_lig_num_comps (c->buffer->cur());
unsigned int components_so_far = last_num_components;
if (!is_mark_ligature)
set_lig_props_for_ligature (c->buffer->cur(), lig_id, total_component_count);
c->replace_glyph (lig_glyph, klass);
for (unsigned int i = 1; i < count; i++)
{
while (c->should_mark_skip_current_glyph ())
{
if (!is_mark_ligature) {
unsigned int new_lig_comp = components_so_far - last_num_components +
MIN (MAX (get_lig_comp (c->buffer->cur()), 1u), last_num_components);
set_lig_props_for_mark (c->buffer->cur(), lig_id, new_lig_comp);
}
c->buffer->next_glyph ();
}
last_lig_id = get_lig_id (c->buffer->cur());
last_num_components = get_lig_num_comps (c->buffer->cur());
components_so_far += last_num_components;
/* Skip the base glyph */
c->buffer->idx++;
}
if (!is_mark_ligature && last_lig_id) {
/* Re-adjust components for any marks following. */
for (unsigned int i = c->buffer->idx; i < c->buffer->len; i++) {
if (last_lig_id == get_lig_id (c->buffer->info[i])) {
unsigned int new_lig_comp = components_so_far - last_num_components +
MIN (MAX (get_lig_comp (c->buffer->info[i]), 1u), last_num_components);
set_lig_props_for_mark (c->buffer->info[i], lig_id, new_lig_comp);
} else
break;
}
}
}
static inline bool match_backtrack (hb_apply_context_t *c,
unsigned int count,