Fixed remaining issues in subpixel positioning with FreeType

1. Merge QStaticText and QGlyphs drawing code of raster engine
   into glyph drawing code for normal QTextItem, it simplify
   the caching system (we don't use QImageTextureGlyphCache for
   raster anymore, just glyph set cache in FreeType engine is
   enough), and fix some regressions in QStaticText and QGlyphs
   drawing.

2. Fix subpixel positioning support for OpenGL texture glyph
   cache. Including a transform handling regression introduced
   by the initial patch.

3. Disable subpixel positioning for bitmap fonts (mono format).

After this change, we only have two code paths for glyph rendering
with FreeType: raster will always use the simple code path (with
QFontEngine_FT cache) while GL will always use QTextureGlyphCache.

Reviewed-by: Eskil

1 files changed, 125 insertions, 125 deletions

diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index 3af98d6..d6cd98b 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -3076,65 +3076,147 @@ void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx
         blend(current, spans, &s->penData);
 }
 
-void QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs,
+bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs,
                                           const QFixedPoint *positions, QFontEngine *fontEngine)
 {
     Q_D(QRasterPaintEngine);
     QRasterPaintEngineState *s = state();
 
-    QFontEngineGlyphCache::Type glyphType = fontEngine->glyphFormat >= 0 ? QFontEngineGlyphCache::Type(fontEngine->glyphFormat) : d->glyphCacheType;
+#if !defined(QT_NO_FREETYPE)
+    if (fontEngine->type() == QFontEngine::Freetype) {
+        QFontEngineFT *fe = static_cast<QFontEngineFT *>(fontEngine);
+        QFontEngineFT::GlyphFormat neededFormat = fe->defaultGlyphFormat();
 
-    QImageTextureGlyphCache *cache =
-        static_cast<QImageTextureGlyphCache *>(fontEngine->glyphCache(0, glyphType, s->matrix));
-    if (!cache) {
-        cache = new QImageTextureGlyphCache(glyphType, s->matrix);
-        fontEngine->setGlyphCache(0, cache);
-    }
+        if (d_func()->mono_surface
+            || fe->isBitmapFont() // alphaPenBlt can handle mono, too
+            )
+            neededFormat = QFontEngineFT::Format_Mono;
 
-    cache->populate(fontEngine, numGlyphs, glyphs, positions);
-    cache->fillInPendingGlyphs();
+        if (neededFormat == QFontEngineFT::Format_None)
+            neededFormat = QFontEngineFT::Format_A8;
 
-    const QImage &image = cache->image();
-    int bpl = image.bytesPerLine();
+        QFontEngineFT::QGlyphSet *gset = fe->defaultGlyphs();
+        if (s->matrix.type() >= QTransform::TxScale) {
+            if (s->matrix.isAffine())
+                gset = fe->loadTransformedGlyphSet(s->matrix);
+            else
+                gset = 0;
+        }
 
-    int depth = image.depth();
-    int rightShift = 0;
-    int leftShift = 0;
-    if (depth == 32)
-        leftShift = 2; // multiply by 4
-    else if (depth == 1)
-        rightShift = 3; // divide by 8
+        if (!gset || gset->outline_drawing
+            || !fe->loadGlyphs(gset, glyphs, numGlyphs, positions, neededFormat))
+            return false;
 
-    int margin = cache->glyphMargin();
+        FT_Face lockedFace = 0;
 
-    bool supportsSubPixelPositions = fontEngine->supportsSubPixelPositions();
+        int depth;
+        switch (neededFormat) {
+        case QFontEngineFT::Format_Mono:
+            depth = 1;
+            break;
+        case QFontEngineFT::Format_A8:
+            depth = 8;
+            break;
+        case QFontEngineFT::Format_A32:
+            depth = 32;
+            break;
+        default:
+            Q_ASSERT(false);
+            depth = 0;
+        };
 
-    const uchar *bits = image.bits();
-    for (int i=0; i<numGlyphs; ++i) {
+        for (int i = 0; i < numGlyphs; i++) {
+            QFixed spp = fe->subPixelPositionForX(positions[i].x);
+            QFontEngineFT::Glyph *glyph = gset->getGlyph(glyphs[i], spp);
 
-        QFixed subPixelPosition;
-        if (supportsSubPixelPositions)
-            subPixelPosition = cache->subPixelPositionForX(positions[i].x);
-        QTextureGlyphCache::GlyphAndSubPixelPosition glyph(glyphs[i], subPixelPosition);
-        const QTextureGlyphCache::Coord &c = cache->coords[glyph];
-        if (c.isNull())
-            continue;
+            if (!glyph || glyph->format != neededFormat) {
+                if (!lockedFace)
+                    lockedFace = fe->lockFace();
+                glyph = fe->loadGlyph(gset, glyphs[i], spp, neededFormat);
+            }
+
+            if (!glyph || !glyph->data)
+                continue;
+
+            int pitch;
+            switch (neededFormat) {
+            case QFontEngineFT::Format_Mono:
+                pitch = ((glyph->width + 31) & ~31) >> 3;
+                break;
+            case QFontEngineFT::Format_A8:
+                pitch = (glyph->width + 3) & ~3;
+                break;
+            case QFontEngineFT::Format_A32:
+                pitch = glyph->width * 4;
+                break;
+            default:
+                Q_ASSERT(false);
+                pitch = 0;
+            };
+
+            alphaPenBlt(glyph->data, pitch, depth,
+                        qFloor(positions[i].x) + glyph->x,
+                        qFloor(positions[i].y) - glyph->y,
+                        glyph->width, glyph->height);
+        }
+        if (lockedFace)
+            fe->unlockFace();
+    } else
+#endif
+    {
+        QFontEngineGlyphCache::Type glyphType = fontEngine->glyphFormat >= 0 ? QFontEngineGlyphCache::Type(fontEngine->glyphFormat) : d->glyphCacheType;
 
-        int x = qFloor(positions[i].x) + c.baseLineX - margin;
-        int y = qFloor(positions[i].y) - c.baseLineY - margin;
+        QImageTextureGlyphCache *cache =
+            static_cast<QImageTextureGlyphCache *>(fontEngine->glyphCache(0, glyphType, s->matrix));
+        if (!cache) {
+            cache = new QImageTextureGlyphCache(glyphType, s->matrix);
+            fontEngine->setGlyphCache(0, cache);
+        }
 
-//         printf("drawing [%d %d %d %d] baseline [%d %d], glyph: %d, to: %d %d, pos: %d %d\n",
-//                c.x, c.y,
-//                c.w, c.h,
-//                c.baseLineX, c.baseLineY,
-//                glyphs[i],
-//                x, y,
-//                positions[i].x.toInt(), positions[i].y.toInt());
+        cache->populate(fontEngine, numGlyphs, glyphs, positions);
+        cache->fillInPendingGlyphs();
 
-        alphaPenBlt(bits + ((c.x << leftShift) >> rightShift) + c.y * bpl, bpl, depth, x, y, c.w, c.h);
-    }
+        const QImage &image = cache->image();
+        int bpl = image.bytesPerLine();
 
-    return;
+        int depth = image.depth();
+        int rightShift = 0;
+        int leftShift = 0;
+        if (depth == 32)
+            leftShift = 2; // multiply by 4
+        else if (depth == 1)
+            rightShift = 3; // divide by 8
+
+        int margin = cache->glyphMargin();
+
+        bool supportsSubPixelPositions = fontEngine->supportsSubPixelPositions();
+
+        const uchar *bits = image.bits();
+        for (int i=0; i<numGlyphs; ++i) {
+
+            QFixed subPixelPosition;
+            if (supportsSubPixelPositions)
+                subPixelPosition = cache->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) + c.baseLineX - margin;
+            int y = qFloor(positions[i].y) - c.baseLineY - margin;
+
+            // printf("drawing [%d %d %d %d] baseline [%d %d], glyph: %d, to: %d %d, pos: %d %d\n",
+            //        c.x, c.y,
+            //        c.w, c.h,
+            //        c.baseLineX, c.baseLineY,
+            //        glyphs[i],
+            //        x, y,
+            //        positions[i].x.toInt(), positions[i].y.toInt());
+
+            alphaPenBlt(bits + ((c.x << leftShift) >> rightShift) + c.y * bpl, bpl, depth, x, y, c.w, c.h);
+        }
+    }
+    return true;
 }
 
 #if defined(Q_OS_SYMBIAN) && defined(QT_NO_FREETYPE)
@@ -3445,92 +3527,10 @@ void QRasterPaintEngine::drawTextItem(const QPointF &p, const QTextItem &textIte
     if (glyphs.size() == 0)
         return;
 
-    // only use subpixel antialiasing when drawing to widgets
-    QFontEngineFT::GlyphFormat neededFormat =
-        painter()->device()->devType() == QInternal::Widget
-        ? fe->defaultGlyphFormat()
-        : QFontEngineFT::Format_A8;
-
-    if (d_func()->mono_surface
-        || fe->isBitmapFont() // alphaPenBlt can handle mono, too
-        )
-        neededFormat = QFontEngineFT::Format_Mono;
-
-    if (neededFormat == QFontEngineFT::Format_None)
-        neededFormat = QFontEngineFT::Format_A8;
-
-    QFontEngineFT::QGlyphSet *gset = fe->defaultGlyphs();
-    if (s->matrix.type() >= QTransform::TxScale) {
-        if (s->matrix.isAffine())
-            gset = fe->loadTransformedGlyphSet(s->matrix);
-        else
-            gset = 0;
-
-    }
-
-    if (!gset || gset->outline_drawing
-        || !fe->loadGlyphs(gset, glyphs.data(), glyphs.size(), positions, neededFormat))
-    {
+    if (!drawCachedGlyphs(glyphs.size(), glyphs.constData(), positions.constData(), ti.fontEngine))
         QPaintEngine::drawTextItem(p, ti);
-        return;
-    }
-
-    FT_Face lockedFace = 0;
-
-    int depth;
-    switch (neededFormat) {
-    case QFontEngineFT::Format_Mono:
-        depth = 1;
-        break;
-    case QFontEngineFT::Format_A8:
-        depth = 8;
-        break;
-    case QFontEngineFT::Format_A32:
-        depth = 32;
-        break;
-    default:
-        Q_ASSERT(false);
-        depth = 0;
-    };
 
-    for(int i = 0; i < glyphs.size(); i++) {
-        QFixed spp = fe->subPixelPositionForX(positions[i].x);
-        QFontEngineFT::Glyph *glyph = gset->getGlyph(glyphs[i], spp);
-
-        if (!glyph || glyph->format != neededFormat) {
-            if (!lockedFace)
-                lockedFace = fe->lockFace();
-            glyph = fe->loadGlyph(gset, glyphs[i], spp, neededFormat);
-        }
-
-        if (!glyph || !glyph->data)
-            continue;
-
-        int pitch;
-        switch (neededFormat) {
-        case QFontEngineFT::Format_Mono:
-            pitch = ((glyph->width + 31) & ~31) >> 3;
-            break;
-        case QFontEngineFT::Format_A8:
-            pitch = (glyph->width + 3) & ~3;
-            break;
-        case QFontEngineFT::Format_A32:
-            pitch = glyph->width * 4;
-            break;
-        default:
-            Q_ASSERT(false);
-            pitch = 0;
-        };
-
-        alphaPenBlt(glyph->data, pitch, depth,
-                    qFloor(positions[i].x) + glyph->x,
-                    qFloor(positions[i].y) - glyph->y,
-                    glyph->width, glyph->height);
-    }
-    if (lockedFace)
-        fe->unlockFace();
     return;
-
 #endif
 #endif