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Disable GSUB feature when text contains surrogates

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This is a work-around for a feature missing in Harfbuzz that
can make a text run that contains a surrogate and a ligature
crash. This will potentially cause the ligatures to break up
if you combine them with a surrogate, causing visual changes
to the text, but the scripts that require GSUB should not be
affected by this, since they will not use surrogates. Still,
it's not a permanent fix, but will serve as a bandaid for the
crash until the underlying problem has been fixed.

Task-number: QTBUG-22275
Change-Id: I90c37fba76bc7d1f369f3afddd1bd0dc306f5750
Reviewed-by: Jiang Jiang <jiang.jiang@nokia.com>
This commit is contained in:
Eskil Abrahamsen Blomfeldt 2012-05-22 12:29:54 +02:00 committed by Qt by Nokia
parent 291b05e4b2
commit 2e6b8b4734
1 changed files with 12 additions and 1 deletions
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13
src/3rdparty/harfbuzz/src/harfbuzz-shaper.cpp vendored
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@ -882,6 +882,17 @@ HB_Bool HB_SelectScript(HB_ShaperItem *shaper_item, const HB_OpenTypeFeature *fe
return true;
}
static HB_Bool containsSurrogates(HB_ShaperItem *item)
{
for (hb_uint32 i=0; i<item->stringLength; ++i) {
HB_UChar16 ucs = item->string[i];
if ( HB_IsHighSurrogate(ucs) || HB_IsLowSurrogate(ucs) )
return true;
}
return false;
}
HB_Bool HB_OpenTypeShape(HB_ShaperItem *item, const hb_uint32 *properties)
{
HB_GlyphAttributes *tmpAttributes;
@ -921,7 +932,7 @@ HB_Bool HB_OpenTypeShape(HB_ShaperItem *item, const hb_uint32 *properties)
#endif
face->glyphs_substituted = false;
if (face->gsub) {
if (face->gsub && !containsSurrogates(item)) {
unsigned int error = HB_GSUB_Apply_String(face->gsub, face->buffer);
if (error && error != HB_Err_Not_Covered)
return false;