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REG: Fix unwanted cache flush in Freetype engine

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The Freetype cache was almost completely disabled by
134c6db858 because after that
change, the lockedAlphaMapForGlyph() function would no longer
cut off early for empty glyphs like spaces, but rather go
through all alpha map functions before it realized that there
was nothing to render. This would in turn invalidate the cache
for every empty glyph, causing all glyphs to be rerendered for
every isolated word.

This change adds back a cut off. This is only needed in the
lockedAlphaMapForGlyph() function, since the superclass implementation
of the other alpha map functions already contains a cut off for
width/height == 0.

[ChangeLog][Qt Gui][Text] Fixed a performance regression in Freetype
engine that was introduced in Qt 5.5.

Change-Id: I381285939909e99cc5fb5f3497fecf9fa871f29a
Task-number: QTBUG-49452
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
This commit is contained in:
Eskil Abrahamsen Blomfeldt 2016-08-01 13:39:53 +02:00
parent 3f1048cca7
commit 6f423555eb
1 changed files with 5 additions and 1 deletions
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6
src/gui/text/qfontengine_ft.cpp
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@ -1716,7 +1716,7 @@ glyph_metrics_t QFontEngineFT::alphaMapBoundingBox(glyph_t glyph, QFixed subPixe
static inline QImage alphaMapFromGlyphData(QFontEngineFT::Glyph *glyph, QFontEngine::GlyphFormat glyphFormat)
{
if (glyph == Q_NULLPTR)
if (glyph == Q_NULLPTR || glyph->height == 0 || glyph->width == 0)
return QImage();
QImage::Format format = QImage::Format_Invalid;
@ -1764,11 +1764,15 @@ QImage *QFontEngineFT::lockedAlphaMapForGlyph(glyph_t glyphIndex, QFixed subPixe
currentlyLockedAlphaMap = alphaMapFromGlyphData(glyph, neededFormat);
const bool glyphHasGeometry = glyph != Q_NULLPTR && glyph->height != 0 && glyph->width != 0;
if (!cacheEnabled && glyph != &emptyGlyph) {
currentlyLockedAlphaMap = currentlyLockedAlphaMap.copy();
delete glyph;
}
if (!glyphHasGeometry)
return Q_NULLPTR;
if (currentlyLockedAlphaMap.isNull())
return QFontEngine::lockedAlphaMapForGlyph(glyphIndex, subPixelPosition, neededFormat, t, offset);