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[coretext] Speed up CoreText font fallback

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Fixes https://code.google.com/p/chromium/issues/detail?id=547912
This commit is contained in:
Behdad Esfahbod 2016-01-11 12:28:37 +00:00
parent 5afebbdcb2
commit a39ff95fce
1 changed files with 40 additions and 5 deletions
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45
src/hb-coretext.cc
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@ -176,6 +176,43 @@ _hb_coretext_shaper_font_data_create (hb_font_t *font)
return NULL;
}
/* Create font copy with cascade list that has LastResort first; this speeds up CoreText
* font fallback which we don't need anyway. */
{
// TODO Handle allocation failures?
CTFontDescriptorRef last_resort = CTFontDescriptorCreateWithNameAndSize(CFSTR("LastResort"), 0);
CFArrayRef cascade_list = CFArrayCreate (kCFAllocatorDefault,
(const void **) &last_resort,
1,
&kCFTypeArrayCallBacks);
CFRelease (last_resort);
CFDictionaryRef attributes = CFDictionaryCreate (kCFAllocatorDefault,
(const void **) &kCTFontCascadeListAttribute,
(const void **) &cascade_list,
1,
&kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
CFRelease (cascade_list);
CTFontDescriptorRef new_font_desc = CTFontDescriptorCreateWithAttributes (attributes);
CFRelease (attributes);
CTFontRef new_ct_font = CTFontCreateCopyWithAttributes (data->ct_font, 0.0, NULL, new_font_desc);
if (new_ct_font)
{
CFRelease (data->ct_font);
data->ct_font = new_ct_font;
}
else
DEBUG_MSG (CORETEXT, font, "Font copy with empty cascade list failed");
}
if (unlikely (!data->ct_font)) {
DEBUG_MSG (CORETEXT, font, "Font CTFontCreateWithGraphicsFont() failed");
free (data);
return NULL;
}
return data;
}
@ -847,11 +884,9 @@ resize_and_retry:
* However, even that wouldn't work if we were passed in the CGFont to
* begin with.
*
* Webkit uses a slightly different approach: it installs LastResort
* as fallback chain, and then checks PS name of used font against
* LastResort. That one is safe for any font except for LastResort,
* as opposed to ours, which can fail if we are using any uninstalled
* font that has the same name as an installed font.
* We might switch to checking PS name against "LastResort". That would
* be safe for all fonts except for those named "Last Resort". Might be
* better than what we have right now.
*
* See: http://github.com/behdad/harfbuzz/pull/36
*/