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Fix subpixel positioning support 

Move subpixelPositionForX from QTextureGlyphCache to QFontEngine,
since some font engines like QFontEngineFT may need a custom
implementation or tweak it a little bit.

In QRasterPaintEngine::drawCachedGlyphs, do not add aliasedCoodinate
to x offset as that will break subpixel positioning.

Change-Id: Idbcec617509459b80965220ceb07b17737649bbf
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>
bb10
Jiang Jiang 2011-11-04 14:47:31 +01:00 committed by Qt by Nokia
parent 04f6983979
commit 63eae1bd15
9 changed files with 27 additions and 42 deletions
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13
src/gui/opengl/qopenglpaintengine.cpp
View File

@ -1536,12 +1536,13 @@ void QOpenGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type
void *cacheKey = ctx->shareGroup();
bool recreateVertexArrays = false;
QFontEngine *fe = staticTextItem->fontEngine();
QOpenGLTextureGlyphCache *cache =
(QOpenGLTextureGlyphCache *) staticTextItem->fontEngine()->glyphCache(cacheKey, glyphType, QTransform());
(QOpenGLTextureGlyphCache *) fe->glyphCache(cacheKey, glyphType, QTransform());
if (!cache || cache->cacheType() != glyphType || cache->contextGroup() == 0) {
cache = new QOpenGLTextureGlyphCache(glyphType, QTransform());
staticTextItem->fontEngine()->setGlyphCache(cacheKey, cache);
fe->setGlyphCache(cacheKey, cache);
recreateVertexArrays = true;
}
@ -1565,11 +1566,11 @@ void QOpenGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type
// cache so this text is performed before we test if the cache size has changed.
if (recreateVertexArrays) {
cache->setPaintEnginePrivate(this);
if (!cache->populate(staticTextItem->fontEngine(), staticTextItem->numGlyphs,
if (!cache->populate(fe, staticTextItem->numGlyphs,
staticTextItem->glyphs, staticTextItem->glyphPositions)) {
// No space for glyphs in cache. We need to reset it and try again.
cache->clear();
cache->populate(staticTextItem->fontEngine(), staticTextItem->numGlyphs,
cache->populate(fe, staticTextItem->numGlyphs,
staticTextItem->glyphs, staticTextItem->glyphPositions);
}
cache->fillInPendingGlyphs();
@ -1620,11 +1621,11 @@ void QOpenGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type
vertexCoordinates->clear();
textureCoordinates->clear();
bool supportsSubPixelPositions = staticTextItem->fontEngine()->supportsSubPixelPositions();
bool supportsSubPixelPositions = fe->supportsSubPixelPositions();
for (int i=0; i<staticTextItem->numGlyphs; ++i) {
QFixed subPixelPosition;
if (supportsSubPixelPositions)
subPixelPosition = cache->subPixelPositionForX(staticTextItem->glyphPositions[i].x);
subPixelPosition = fe->subPixelPositionForX(staticTextItem->glyphPositions[i].x);
QTextureGlyphCache::GlyphAndSubPixelPosition glyph(staticTextItem->glyphs[i], subPixelPosition);

4
src/gui/painting/qpaintengine_raster.cpp
View File

@ -2752,13 +2752,13 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs,
const uchar *bits = image.bits();
for (int i=0; i<numGlyphs; ++i) {
QFixed subPixelPosition = cache->subPixelPositionForX(positions[i].x);
QFixed subPixelPosition = fontEngine->subPixelPositionForX(positions[i].x);
QTextureGlyphCache::GlyphAndSubPixelPosition glyph(glyphs[i], subPixelPosition);
const QTextureGlyphCache::Coord &c = cache->coords[glyph];
if (c.isNull())
continue;
int x = qFloor(positions[i].x + offs) + c.baseLineX - margin;
int x = qFloor(positions[i].x) + c.baseLineX - margin;
int y = qFloor(positions[i].y + offs) - c.baseLineY - margin;
// printf("drawing [%d %d %d %d] baseline [%d %d], glyph: %d, to: %d %d, pos: %d %d\n",

27
src/gui/painting/qtextureglyphcache.cpp
View File

@ -99,23 +99,6 @@ int QTextureGlyphCache::calculateSubPixelPositionCount(glyph_t glyph) const
return images.size();
}
QFixed QTextureGlyphCache::subPixelPositionForX(QFixed x) const
{
if (m_subPixelPositionCount <= 1)
return QFixed();
QFixed subPixelPosition;
if (x != 0) {
subPixelPosition = x - x.floor();
QFixed fraction = (subPixelPosition / QFixed::fromReal(1.0 / m_subPixelPositionCount)).floor();
// Compensate for precision loss in fixed point to make sure we are always drawing at a subpixel position over
// the lower boundary for the selected rasterization by adding 1/64.
subPixelPosition = fraction / QFixed(m_subPixelPositionCount) + QFixed::fromReal(0.015625);
}
return subPixelPosition;
}
bool QTextureGlyphCache::populate(QFontEngine *fontEngine, int numGlyphs, const glyph_t *glyphs,
const QFixedPoint *positions)
{
@ -129,13 +112,13 @@ bool QTextureGlyphCache::populate(QFontEngine *fontEngine, int numGlyphs, const
const int paddingDoubled = glyphPadding() * 2;
bool supportsSubPixelPositions = fontEngine->supportsSubPixelPositions();
if (m_subPixelPositionCount == 0) {
if (fontEngine->m_subPixelPositionCount == 0) {
if (!supportsSubPixelPositions) {
m_subPixelPositionCount = 1;
fontEngine->m_subPixelPositionCount = 1;
} else {
int i = 0;
while (m_subPixelPositionCount == 0 && i < numGlyphs)
m_subPixelPositionCount = calculateSubPixelPositionCount(glyphs[i++]);
while (fontEngine->m_subPixelPositionCount == 0 && i < numGlyphs)
fontEngine->m_subPixelPositionCount = calculateSubPixelPositionCount(glyphs[i++]);
}
}
@ -156,7 +139,7 @@ bool QTextureGlyphCache::populate(QFontEngine *fontEngine, int numGlyphs, const
QFixed subPixelPosition;
if (supportsSubPixelPositions) {
QFixed x = positions != 0 ? positions[i].x : QFixed();
subPixelPosition = subPixelPositionForX(x);
subPixelPosition = fontEngine->subPixelPositionForX(x);
}
if (coords.contains(GlyphAndSubPixelPosition(glyph, subPixelPosition)))

5
src/gui/painting/qtextureglyphcache_p.h
View File

@ -81,7 +81,7 @@ class Q_GUI_EXPORT QTextureGlyphCache : public QFontEngineGlyphCache
public:
QTextureGlyphCache(QFontEngineGlyphCache::Type type, const QTransform &matrix)
: QFontEngineGlyphCache(matrix, type), m_current_fontengine(0),
m_w(0), m_h(0), m_cx(0), m_cy(0), m_currentRowHeight(0), m_subPixelPositionCount(0)
m_w(0), m_h(0), m_cx(0), m_cy(0), m_currentRowHeight(0)
{ }
virtual ~QTextureGlyphCache() { }
@ -146,8 +146,6 @@ public:
QImage textureMapForGlyph(glyph_t g, QFixed subPixelPosition) const;
QFixed subPixelPositionForX(QFixed x) const;
protected:
int calculateSubPixelPositionCount(glyph_t) const;
@ -159,7 +157,6 @@ protected:
int m_cx; // current x
int m_cy; // current y
int m_currentRowHeight; // Height of last row
int m_subPixelPositionCount; // Number of positions within a single pixel for this cache
};
inline uint qHash(const QTextureGlyphCache::GlyphAndSubPixelPosition &g)

13
src/gui/text/qfontengine.cpp
View File

@ -179,6 +179,7 @@ QFontEngine::QFontEngine()
hbFace = 0;
glyphFormat = -1;
m_subPixelPositionCount = 0;
}
QFontEngine::~QFontEngine()
@ -635,17 +636,19 @@ QImage QFontEngine::alphaRGBMapForGlyph(glyph_t glyph, QFixed /*subPixelPosition
return rgbMask;
}
QFixed QFontEngine::subPixelPositionForX(QFixed x)
QFixed QFontEngine::subPixelPositionForX(QFixed x) const
{
int m_subPixelPositionCount = 4;
if (!supportsSubPixelPositions())
return 0;
if (m_subPixelPositionCount <= 1 || !supportsSubPixelPositions())
return QFixed();
QFixed subPixelPosition;
if (x != 0) {
subPixelPosition = x - x.floor();
QFixed fraction = (subPixelPosition / QFixed::fromReal(1.0 / m_subPixelPositionCount)).floor();
subPixelPosition = fraction / QFixed(m_subPixelPositionCount);
// Compensate for precision loss in fixed point to make sure we are always drawing at a subpixel position over
// the lower boundary for the selected rasterization by adding 1/64.
subPixelPosition = fraction / QFixed(m_subPixelPositionCount) + QFixed::fromReal(0.015625);
}
return subPixelPosition;
}

1
src/gui/text/qfontengine_ft.cpp
View File

@ -657,6 +657,7 @@ QFontEngineFT::QFontEngineFT(const QFontDef &fd)
defaultFormat = Format_None;
embeddedbitmap = false;
cacheEnabled = qgetenv("QT_NO_FT_CACHE").isEmpty() || qgetenv("QT_NO_FT_CACHE").toInt() == 0;
m_subPixelPositionCount = 4;
}
QFontEngineFT::~QFontEngineFT()

1
src/gui/text/qfontengine_ft_p.h
View File

@ -315,7 +315,6 @@ private:
bool initFromFontEngine(const QFontEngineFT *fontEngine);
HintStyle defaultHintStyle() const { return default_hint_style; }
protected:
QFreetypeFace *freetype;

3
src/gui/text/qfontengine_p.h
View File

@ -158,7 +158,7 @@ public:
};
virtual int synthesized() const { return 0; }
virtual bool supportsSubPixelPositions() const { return false; }
QFixed subPixelPositionForX(QFixed x);
virtual QFixed subPixelPositionForX(QFixed x) const;
virtual QFixed emSquareSize() const { return ascent(); }
@ -277,6 +277,7 @@ public:
int glyphFormat;
QImage currentlyLockedAlphaMap;
int m_subPixelPositionCount; // Number of positions within a single pixel for this cache
protected:
static const QVector<QRgb> &grayPalette();

2
src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
View File

@ -1654,7 +1654,7 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
for (int i=0; i<staticTextItem->numGlyphs; ++i) {
QFixed subPixelPosition;
if (supportsSubPixelPositions)
subPixelPosition = cache->subPixelPositionForX(staticTextItem->glyphPositions[i].x);
subPixelPosition = staticTextItem->fontEngine()->subPixelPositionForX(staticTextItem->glyphPositions[i].x);
QTextureGlyphCache::GlyphAndSubPixelPosition glyph(staticTextItem->glyphs[i], subPixelPosition);