Fixed text rendering via scaled QPainter on rasterPaintEngine / Symbian

Text rendering in Qt for Symbian looks very bad on a scaled QPainter.

Instead of simply using a Symbian font with the right size it followed
the code path that is usually used for "tricky transformation":
Use the glyph outlines and rasterize them in Qt as QPainterPath.
That's slow and especially ugly on Symbian since we do not (yet)
get the glyph outlines from Symbian.

This patch adds QFontEngineS60::setFontScale() so that QFontEngineS60
has one additional native font handle with the scaled size. The raster
paint engine will call that function in case that the painter is scaled.
Since we already have QFontEngineS60 specific code in the raster paint
engine, this patch did not have to add #ifdefs.

http://bugreports.qt.nokia.com/browse/QTBUG-7614

Task-number: QTBUG-7614
Reviewed-by: Jason Barron

	modified:   gui/painting/qpaintengine_raster.cpp
	modified:   gui/text/qfontengine_s60.cpp
	modified:   gui/text/qfontengine_s60_p.h

2 files changed, 60 insertions, 18 deletions

diff --git a/src/gui/text/qfontengine_s60.cpp b/src/gui/text/qfontengine_s60.cpp
index 4625667..9dd4af7 100644
--- a/src/gui/text/qfontengine_s60.cpp
+++ b/src/gui/text/qfontengine_s60.cpp
@@ -129,26 +129,62 @@ static inline unsigned int getChar(const QChar *str, int &i, const int len)
     return uc;
 }
 
+CFont *QFontEngineS60::fontWithSize(qreal size) const
+{
+    CFont *result = 0;
+    TFontSpec fontSpec(qt_QString2TPtrC(QFontEngine::fontDef.family), TInt(size));
+    fontSpec.iFontStyle.SetBitmapType(EAntiAliasedGlyphBitmap);
+    fontSpec.iFontStyle.SetPosture(QFontEngine::fontDef.style == QFont::StyleNormal?EPostureUpright:EPostureItalic);
+    fontSpec.iFontStyle.SetStrokeWeight(QFontEngine::fontDef.weight > QFont::Normal?EStrokeWeightBold:EStrokeWeightNormal);
+    const TInt errorCode = S60->screenDevice()->GetNearestFontToDesignHeightInPixels(result, fontSpec);
+    Q_ASSERT(result && (errorCode == 0));
+    return result;
+}
+
+void QFontEngineS60::setFontScale(qreal scale)
+{
+    if (qFuzzyCompare(scale, qreal(1))) {
+        if (!m_originalFont)
+            m_originalFont = fontWithSize(m_originalFontSizeInPixels);
+        m_activeFont = m_originalFont;
+    } else {
+        const qreal scaledFontSizeInPixels = m_originalFontSizeInPixels * scale;
+        if (!m_scaledFont ||
+                (TInt(scaledFontSizeInPixels) != TInt(m_scaledFontSizeInPixels))) {
+            releaseFont(m_scaledFont);
+            m_scaledFontSizeInPixels = scaledFontSizeInPixels;
+            m_scaledFont = fontWithSize(m_scaledFontSizeInPixels);
+        }
+        m_activeFont = m_scaledFont;
+    }
+}
+
+void QFontEngineS60::releaseFont(CFont *&font)
+{
+    if (font) {
+        S60->screenDevice()->ReleaseFont(font);
+        font = 0;
+    }
+}
+
 QFontEngineS60::QFontEngineS60(const QFontDef &request, const QFontEngineS60Extensions *extensions)
     : m_extensions(extensions)
+    , m_originalFont(0)
+    , m_originalFontSizeInPixels((request.pixelSize >= 0)?
+            request.pixelSize:pointsToPixels(request.pointSize))
+    , m_scaledFont(0)
+    , m_scaledFontSizeInPixels(0)
+    , m_activeFont(0)
 {
     QFontEngine::fontDef = request;
-    m_fontSizeInPixels = (request.pixelSize >= 0)?
-            request.pixelSize:pointsToPixels(request.pointSize);
-
-    TFontSpec fontSpec(qt_QString2TPtrC(request.family), m_fontSizeInPixels);
-    fontSpec.iFontStyle.SetBitmapType(EAntiAliasedGlyphBitmap);
-    fontSpec.iFontStyle.SetPosture(request.style == QFont::StyleNormal?EPostureUpright:EPostureItalic);
-    fontSpec.iFontStyle.SetStrokeWeight(request.weight > QFont::Normal?EStrokeWeightBold:EStrokeWeightNormal);
-    const TInt errorCode = S60->screenDevice()->GetNearestFontToDesignHeightInPixels(m_font, fontSpec);
-    Q_ASSERT(errorCode == 0);
-
+    setFontScale(1.0);
     cache_cost = sizeof(QFontEngineS60);
 }
 
 QFontEngineS60::~QFontEngineS60()
 {
-    S60->screenDevice()->ReleaseFont(m_font);
+    releaseFont(m_originalFont);
+    releaseFont(m_scaledFont);
 }
 
 bool QFontEngineS60::stringToCMap(const QChar *characters, int len, QGlyphLayout *glyphs, int *nglyphs, QTextEngine::ShaperFlags flags) const
@@ -251,12 +287,12 @@ glyph_metrics_t QFontEngineS60::boundingBox(glyph_t glyph)
 
 QFixed QFontEngineS60::ascent() const
 {
-    return m_font->FontMaxAscent();
+    return m_originalFont->FontMaxAscent();
 }
 
 QFixed QFontEngineS60::descent() const
 {
-    return m_font->FontMaxDescent();
+    return m_originalFont->FontMaxDescent();
 }
 
 QFixed QFontEngineS60::leading() const
@@ -266,7 +302,7 @@ QFixed QFontEngineS60::leading() const
 
 qreal QFontEngineS60::maxCharWidth() const
 {
-    return m_font->MaxCharWidthInPixels();
+    return m_originalFont->MaxCharWidthInPixels();
 }
 
 const char *QFontEngineS60::name() const
@@ -302,11 +338,11 @@ void QFontEngineS60::getCharacterData(glyph_t glyph, TOpenFontCharMetrics& metri
     const TUint specialCode = (TUint)glyph | 0x80000000;
 
     const CFont::TCharacterDataAvailability availability =
-        m_font->GetCharacterData(specialCode, metrics, bitmap, bitmapSize);
+            m_activeFont->GetCharacterData(specialCode, metrics, bitmap, bitmapSize);
     const glyph_t fallbackGlyph = '?';
     if (availability != CFont::EAllCharacterData) {
         const CFont::TCharacterDataAvailability fallbackAvailability =
-            m_font->GetCharacterData(fallbackGlyph, metrics, bitmap, bitmapSize);
+                m_activeFont->GetCharacterData(fallbackGlyph, metrics, bitmap, bitmapSize);
         Q_ASSERT(fallbackAvailability == CFont::EAllCharacterData);
     }
 }
diff --git a/src/gui/text/qfontengine_s60_p.h b/src/gui/text/qfontengine_s60_p.h
index 4748497..78f8a9a 100644
--- a/src/gui/text/qfontengine_s60_p.h
+++ b/src/gui/text/qfontengine_s60_p.h
@@ -117,15 +117,21 @@ public:
     Type type() const;
 
     void getCharacterData(glyph_t glyph, TOpenFontCharMetrics& metrics, const TUint8*& bitmap, TSize& bitmapSize) const;
+    void setFontScale(qreal scale);
 
 private:
     friend class QFontPrivate;
 
     QFixed glyphAdvance(HB_Glyph glyph) const;
+    CFont *fontWithSize(qreal size) const;
+    static void releaseFont(CFont *&font);
 
-    CFont* m_font;
     const QFontEngineS60Extensions *m_extensions;
-    qreal m_fontSizeInPixels;
+    CFont* m_originalFont;
+    const qreal m_originalFontSizeInPixels;
+    CFont* m_scaledFont;
+    qreal m_scaledFontSizeInPixels;
+    CFont* m_activeFont;
 };
 
 class QFontEngineMultiS60 : public QFontEngineMulti