Thanks Jonathan. Can you test my alternate approach? Attached.
On 13-09-27 11:22 AM, Jonathan Kew wrote:
> Hi Behdad,
>
> With the change in variation selector handling, stray (unsupported) VS codes
> are no longer consumed by the get_glyph callback; they remain in the buffer
> and are individually mapped to glyphs. That's all very well; but in most cases
> they'll just map to .notdef.
>
> Eventually, hb_ot_hide_default_ignorables() will run across these .notdef
> glyphs and replace them with zero-width space glyphs. All's good...
>
> ...except in the (unlikely) case where the font does not actually support the
> <space> character. This will be almost vanishingly rare, of course - but
> unfortunately it happens with the "MarkA" font that's used for a variety of
> rendering tests.
>
> This prompted me to look into patching hb_ot_hide_default_ignorables() so that
> it will work even if there's no <space> in the font. ISTM we can fix this by
> simply deleting the ignorable altogether in this case. It'll be a bit less
> performant than the current replace-with-zero-width-space implementation,
> because it requires shifting all the following glyphs up in the buffer, so
> I've retained the existing implementation for the (usual) case where <space>
> is available.
>
> Suggested patch is attached.
>
> JK
--
behdad
http://behdad.org/
diff --git a/src/hb-ot-shape.cc b/src/hb-ot-shape.cc
index 15f4461..d6abafc 100644
--- a/src/hb-ot-shape.cc
+++ b/src/hb-ot-shape.cc
@@ -533,22 +533,42 @@ hb_ot_hide_default_ignorables (hb_ot_shape_context_t *c)
if (c->buffer->flags & HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES)
return;
- hb_codepoint_t space = 0;
+ hb_codepoint_t space;
+ enum {
+ SPACE_DONT_KNOW,
+ SPACE_AVAILABLE,
+ SPACE_UNAVAILABLE
+ } space_status = SPACE_DONT_KNOW;
unsigned int count = c->buffer->len;
+ hb_glyph_info_t *info = c->buffer->info;
+ hb_glyph_position_t *pos = c->buffer->pos;
+ unsigned int j = 0;
for (unsigned int i = 0; i < count; i++)
- if (unlikely (!is_a_ligature (c->buffer->info[i]) &&
- _hb_glyph_info_is_default_ignorable (&c->buffer->info[i])))
+ {
+ if (unlikely (!is_a_ligature (info[i]) &&
+ _hb_glyph_info_is_default_ignorable (&info[i])))
{
- if (!space) {
- /* We assume that the space glyph is not gid0. */
- if (unlikely (!c->font->get_glyph (' ', 0, &space)) || !space)
- return; /* No point! */
+ if (space_status == SPACE_DONT_KNOW)
+ space_status = c->font->get_glyph (' ', 0, &space) ? SPACE_AVAILABLE : SPACE_UNAVAILABLE;
+
+ if (space_status == SPACE_AVAILABLE)
+ {
+ info[i].codepoint = space;
+ pos[i].x_advance = 0;
+ pos[i].y_advance = 0;
}
- c->buffer->info[i].codepoint = space;
- c->buffer->pos[i].x_advance = 0;
- c->buffer->pos[i].y_advance = 0;
+ else
+ continue; /* Delete it. */
+ }
+ j++;
+ if (j != i)
+ {
+ info[j] = info[i];
+ pos[j] = pos[i];
}
+ }
+ c->buffer->len = j;
}
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