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[OT] Do per-ligature-component fallback mark positioning 

With this in place, you can remove GDEF/GSUB/GPOS tables from Arabic
fonts and still get per-component marks positioned on
oh-yeah-fallback-formed LAM-ALEF ligatures with marks in between the LAM
and ALEF.

Now *that*'s pretty cool, if a bit anachronistic...
This commit is contained in:
Behdad Esfahbod 2012-09-06 17:22:31 -04:00
parent 525c685578
commit f67917161b
1 changed files with 36 additions and 7 deletions
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43
src/hb-ot-shape-fallback.cc
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@ -287,6 +287,7 @@ position_around_base (const hb_ot_shape_plan_t *plan,
unsigned int base,
unsigned int end)
{
hb_direction_t horiz_dir = HB_DIRECTION_INVALID;
hb_glyph_extents_t base_extents;
if (!font->get_glyph_extents (buffer->info[base].codepoint,
&base_extents))
@ -298,22 +299,53 @@ position_around_base (const hb_ot_shape_plan_t *plan,
base_extents.x_bearing += buffer->pos[base].x_offset;
base_extents.y_bearing += buffer->pos[base].y_offset;
/* XXX Handle ligature component positioning... */
HB_UNUSED bool is_ligature = is_a_ligature (buffer->info[base]);
unsigned int lig_id = get_lig_id (buffer->info[base]);
unsigned int num_lig_components = get_lig_num_comps (buffer->info[base]);
hb_position_t x_offset = 0, y_offset = 0;
if (HB_DIRECTION_IS_FORWARD (buffer->props.direction)) {
x_offset -= buffer->pos[base].x_advance;
y_offset -= buffer->pos[base].y_advance;
}
hb_glyph_extents_t component_extents = base_extents;
unsigned int last_lig_component = (unsigned int) -1;
unsigned int last_combining_class = 255;
hb_glyph_extents_t cluster_extents;
for (unsigned int i = base + 1; i < end; i++)
if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]))
{
if (num_lig_components > 1) {
unsigned int this_lig_id = get_lig_id (buffer->info[i]);
unsigned int this_lig_component = get_lig_comp (buffer->info[i]) - 1;
/* Conditions for attaching to the last component. */
if (!lig_id || lig_id != this_lig_id || this_lig_component >= num_lig_components)
this_lig_component = num_lig_components - 1;
if (last_lig_component != this_lig_component)
{
last_lig_component = this_lig_component;
last_combining_class = 255;
component_extents = base_extents;
if (unlikely (horiz_dir == HB_DIRECTION_INVALID)) {
if (HB_DIRECTION_IS_HORIZONTAL (plan->props.direction))
horiz_dir = plan->props.direction;
else
horiz_dir = hb_script_get_horizontal_direction (plan->props.script);
}
if (horiz_dir == HB_DIRECTION_LTR)
component_extents.x_bearing += (this_lig_component * component_extents.width) / num_lig_components;
else
component_extents.x_bearing += ((num_lig_components - 1 - this_lig_component) * component_extents.width) / num_lig_components;
component_extents.width /= num_lig_components;
}
}
unsigned int this_combining_class = _hb_glyph_info_get_modified_combining_class (&buffer->info[i]);
if (this_combining_class != last_combining_class)
cluster_extents = base_extents;
if (last_combining_class != this_combining_class)
{
last_combining_class = this_combining_class;
cluster_extents = component_extents;
}
position_mark (plan, font, buffer, cluster_extents, i, this_combining_class);
@ -322,7 +354,6 @@ position_around_base (const hb_ot_shape_plan_t *plan,
buffer->pos[i].x_offset += x_offset;
buffer->pos[i].y_offset += y_offset;
last_combining_class = this_combining_class;
} else {
if (HB_DIRECTION_IS_FORWARD (buffer->props.direction)) {
x_offset -= buffer->pos[i].x_advance;
@ -332,8 +363,6 @@ position_around_base (const hb_ot_shape_plan_t *plan,
y_offset += buffer->pos[i].y_advance;
}
}
}
static inline void