Enable gamma-correction on a face-by-face basis

Changes how we control if gamma-correction is done, and enables it for
the freetype CFF engine when stem-darkening is available.

The new code replaces existing hacks to force gamma-correction off
when using Freetype on X11 and Windows.

Change-Id: Ic703ca6965a3d81b204349e10f406c991b292edd
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

15 files changed, 72 insertions, 40 deletions

diff --git a/src/3rdparty/freetype/freetype.pro b/src/3rdparty/freetype/freetype.pro
index 5b1eb92e32..9033ed943c 100644
--- a/src/3rdparty/freetype/freetype.pro
+++ b/src/3rdparty/freetype/freetype.pro
@@ -24,6 +24,7 @@ SOURCES += \
     $$PWD/src/base/ftbbox.c \
     $$PWD/src/base/ftdebug.c \
     $$PWD/src/base/ftglyph.c \
+    $$PWD/src/base/ftfntfmt.c \
     $$PWD/src/base/ftinit.c \
     $$PWD/src/base/ftlcdfil.c \
     $$PWD/src/base/ftmm.c \
diff --git a/src/gui/painting/qdrawhelper.cpp b/src/gui/painting/qdrawhelper.cpp
index 8a9f8b8bdc..6f82ab871c 100644
--- a/src/gui/painting/qdrawhelper.cpp
+++ b/src/gui/painting/qdrawhelper.cpp
@@ -5547,7 +5547,7 @@ static void qt_alphamapblit_quint16(QRasterBuffer *rasterBuffer,
                                     int x, int y, const QRgba64 &color,
                                     const uchar *map,
                                     int mapWidth, int mapHeight, int mapStride,
-                                    const QClipData *)
+                                    const QClipData *, bool /*useGammaCorrection*/)
 {
     const quint16 c = color.toRgb16();
     quint16 *dest = reinterpret_cast<quint16*>(rasterBuffer->scanLine(y)) + x;
@@ -5572,18 +5572,16 @@ static void qt_alphamapblit_quint16(QRasterBuffer *rasterBuffer,
     }
 }
 
-static inline void rgbBlendPixel(quint32 *dst, int coverage, QRgba64 slinear, const QColorProfile *colorProfile)
+static inline void rgbBlendPixel(quint32 *dst, int coverage, QRgba64 slinear, const QColorProfile *colorProfile, bool useGammaCorrection)
 {
     // Do a gammacorrected RGB alphablend...
-    const QRgba64 dlinear = colorProfile->toLinear64(*dst);
+    const QRgba64 dlinear = useGammaCorrection ? colorProfile->toLinear64(*dst) : QRgba64::fromArgb32(*dst);
 
     QRgba64 blend = rgbBlend(dlinear, slinear, coverage);
 
-    *dst = colorProfile->fromLinear64(blend);
+    *dst = useGammaCorrection ? colorProfile->fromLinear64(blend) : toArgb32(blend);
 }
 
-Q_GUI_EXPORT bool qt_needs_a8_gamma_correction = false;
-
 static inline void grayBlendPixel(quint32 *dst, int coverage, QRgba64 slinear, const QColorProfile *colorProfile)
 {
     // Do a gammacorrected gray alphablend...
@@ -5598,7 +5596,7 @@ static void qt_alphamapblit_uint32(QRasterBuffer *rasterBuffer,
                                    int x, int y, quint32 color,
                                    const uchar *map,
                                    int mapWidth, int mapHeight, int mapStride,
-                                   const QClipData *clip)
+                                   const QClipData *clip, bool useGammaCorrection)
 {
     const quint32 c = color;
     const int destStride = rasterBuffer->bytesPerLine() / sizeof(quint32);
@@ -5610,7 +5608,7 @@ static void qt_alphamapblit_uint32(QRasterBuffer *rasterBuffer,
     const QRgba64 slinear = colorProfile->toLinear64(c);
 
     bool opaque_src = (qAlpha(color) == 255);
-    bool doGrayBlendPixel = opaque_src && qt_needs_a8_gamma_correction;
+    bool doGrayBlendPixel = opaque_src && useGammaCorrection;
 
     if (!clip) {
         quint32 *dest = reinterpret_cast<quint32*>(rasterBuffer->scanLine(y)) + x;
@@ -5680,9 +5678,9 @@ static void qt_alphamapblit_argb32(QRasterBuffer *rasterBuffer,
                                    int x, int y, const QRgba64 &color,
                                    const uchar *map,
                                    int mapWidth, int mapHeight, int mapStride,
-                                   const QClipData *clip)
+                                   const QClipData *clip, bool useGammaCorrection)
 {
-    qt_alphamapblit_uint32(rasterBuffer, x, y, color.toArgb32(), map, mapWidth, mapHeight, mapStride, clip);
+    qt_alphamapblit_uint32(rasterBuffer, x, y, color.toArgb32(), map, mapWidth, mapHeight, mapStride, clip, useGammaCorrection);
 }
 
 #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
@@ -5690,9 +5688,9 @@ static void qt_alphamapblit_rgba8888(QRasterBuffer *rasterBuffer,
                                      int x, int y, const QRgba64 &color,
                                      const uchar *map,
                                      int mapWidth, int mapHeight, int mapStride,
-                                     const QClipData *clip)
+                                     const QClipData *clip, bool useGammaCorrection)
 {
-    qt_alphamapblit_uint32(rasterBuffer, x, y, ARGB2RGBA(color.toArgb32()), map, mapWidth, mapHeight, mapStride, clip);
+    qt_alphamapblit_uint32(rasterBuffer, x, y, ARGB2RGBA(color.toArgb32()), map, mapWidth, mapHeight, mapStride, clip, useGammaCorrection);
 }
 #endif
 
@@ -5704,7 +5702,7 @@ inline static int qRgbAvg(QRgb rgb)
 static void qt_alphargbblit_argb32(QRasterBuffer *rasterBuffer,
                                    int x, int y, const QRgba64 &color,
                                    const uint *src, int mapWidth, int mapHeight, int srcStride,
-                                   const QClipData *clip)
+                                   const QClipData *clip, bool useGammaCorrection)
 {
     const quint32 c = color.toArgb32();
 
@@ -5714,7 +5712,7 @@ static void qt_alphargbblit_argb32(QRasterBuffer *rasterBuffer,
     if (!colorProfile)
         return;
 
-    const QRgba64 slinear = colorProfile->toLinear64(c);
+    const QRgba64 slinear = useGammaCorrection ? colorProfile->toLinear64(c) : color;
 
     if (sa == 0)
         return;
@@ -5729,7 +5727,7 @@ static void qt_alphargbblit_argb32(QRasterBuffer *rasterBuffer,
                     dst[i] = c;
                 } else if (coverage != 0xff000000) {
                     if (dst[i] >= 0xff000000) {
-                        rgbBlendPixel(dst+i, coverage, slinear, colorProfile);
+                        rgbBlendPixel(dst+i, coverage, slinear, colorProfile, useGammaCorrection);
                     } else {
                         // Give up and do a naive blend.
                         const int a = qRgbAvg(coverage);
@@ -5765,7 +5763,7 @@ static void qt_alphargbblit_argb32(QRasterBuffer *rasterBuffer,
                         dst[xp] = c;
                     } else if (coverage != 0xff000000) {
                         if (dst[xp] >= 0xff000000) {
-                            rgbBlendPixel(dst+xp, coverage, slinear, colorProfile);
+                            rgbBlendPixel(dst+xp, coverage, slinear, colorProfile, useGammaCorrection);
                         } else {
                             // Give up and do a naive blend.
                             const int a = qRgbAvg(coverage);
diff --git a/src/gui/painting/qdrawhelper_neon.cpp b/src/gui/painting/qdrawhelper_neon.cpp
index a833520b00..cdb374f823 100644
--- a/src/gui/painting/qdrawhelper_neon.cpp
+++ b/src/gui/painting/qdrawhelper_neon.cpp
@@ -539,7 +539,7 @@ void qt_alphamapblit_quint16_neon(QRasterBuffer *rasterBuffer,
                                   int x, int y, const QRgba64 &color,
                                   const uchar *bitmap,
                                   int mapWidth, int mapHeight, int mapStride,
-                                  const QClipData *)
+                                  const QClipData *, bool /*useGammaCorrection*/)
 {
     quint16 *dest = reinterpret_cast<quint16*>(rasterBuffer->scanLine(y)) + x;
     const int destStride = rasterBuffer->bytesPerLine() / sizeof(quint16);
diff --git a/src/gui/painting/qdrawhelper_neon_p.h b/src/gui/painting/qdrawhelper_neon_p.h
index 3cf949fc32..40475a9bde 100644
--- a/src/gui/painting/qdrawhelper_neon_p.h
+++ b/src/gui/painting/qdrawhelper_neon_p.h
@@ -91,7 +91,7 @@ void qt_alphamapblit_quint16_neon(QRasterBuffer *rasterBuffer,
                                   int x, int y, const QRgba64 &color,
                                   const uchar *bitmap,
                                   int mapWidth, int mapHeight, int mapStride,
-                                  const QClipData *clip);
+                                  const QClipData *clip, bool /*useGammaCorrection*/);
 
 void qt_scale_image_argb32_on_rgb16_neon(uchar *destPixels, int dbpl,
                                          const uchar *srcPixels, int sbpl, int srch,
diff --git a/src/gui/painting/qdrawhelper_p.h b/src/gui/painting/qdrawhelper_p.h
index 933da56095..f35b763f93 100644
--- a/src/gui/painting/qdrawhelper_p.h
+++ b/src/gui/painting/qdrawhelper_p.h
@@ -111,13 +111,13 @@ typedef void (*AlphamapBlitFunc)(QRasterBuffer *rasterBuffer,
                                  int x, int y, const QRgba64 &color,
                                  const uchar *bitmap,
                                  int mapWidth, int mapHeight, int mapStride,
-                                 const QClipData *clip);
+                                 const QClipData *clip, bool useGammaCorrection);
 
 typedef void (*AlphaRGBBlitFunc)(QRasterBuffer *rasterBuffer,
                                  int x, int y, const QRgba64 &color,
                                  const uint *rgbmask,
                                  int mapWidth, int mapHeight, int mapStride,
-                                 const QClipData *clip);
+                                 const QClipData *clip, bool useGammaCorrection);
 
 typedef void (*RectFillFunc)(QRasterBuffer *rasterBuffer,
                              int x, int y, int width, int height,
diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index 647bd5cb2c..68b8d78ac6 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -2555,7 +2555,7 @@ QRasterBuffer *QRasterPaintEngine::rasterBuffer()
 /*!
     \internal
 */
-void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx,int ry,int w,int h)
+void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx,int ry,int w,int h, bool useGammaCorrection)
 {
     Q_D(QRasterPaintEngine);
     QRasterPaintEngineState *s = state();
@@ -2610,14 +2610,14 @@ void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx
             } else if (depth == 8) {
                 if (s->penData.alphamapBlit) {
                     s->penData.alphamapBlit(rb, rx, ry, s->penData.solid.color,
-                                            scanline, w, h, bpl, 0);
+                                            scanline, w, h, bpl, 0, useGammaCorrection);
                     return;
                 }
             } else if (depth == 32) {
                 // (A)RGB Alpha mask where the alpha component is not used.
                 if (s->penData.alphaRGBBlit) {
                     s->penData.alphaRGBBlit(rb, rx, ry, s->penData.solid.color,
-                                            (const uint *) scanline, w, h, bpl / 4, 0);
+                                            (const uint *) scanline, w, h, bpl / 4, 0, useGammaCorrection);
                     return;
                 }
             }
@@ -2646,10 +2646,10 @@ void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx
             }
             if (depth == 8)
                 s->penData.alphamapBlit(rb, rx, ry, s->penData.solid.color,
-                                        scanline, w, h, bpl, clip);
+                                        scanline, w, h, bpl, clip, useGammaCorrection);
             else if (depth == 32)
                 s->penData.alphaRGBBlit(rb, rx, ry, s->penData.solid.color,
-                                        (const uint *) scanline, w, h, bpl / 4, clip);
+                                        (const uint *) scanline, w, h, bpl / 4, clip, useGammaCorrection);
             return;
         }
     }
@@ -2807,7 +2807,8 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs,
             alphaPenBlt(alphaMap->constBits(), alphaMap->bytesPerLine(), alphaMap->depth(),
                         qFloor(positions[i].x) + offset.x(),
                         qRound(positions[i].y) + offset.y(),
-                        alphaMap->width(), alphaMap->height());
+                        alphaMap->width(), alphaMap->height(),
+                        fontEngine->expectsGammaCorrectedBlending());
 
             fontEngine->unlockAlphaMapForGlyph();
         }
@@ -2868,7 +2869,7 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs,
                 drawImage(QPoint(x, y), QImage(glyphBits, c.w, c.h, bpl, image.format()));
                 s->matrix = originalTransform;
             } else {
-                alphaPenBlt(glyphBits, bpl, depth, x, y, c.w, c.h);
+                alphaPenBlt(glyphBits, bpl, depth, x, y, c.w, c.h, fontEngine->expectsGammaCorrectedBlending());
             }
         }
     }
diff --git a/src/gui/painting/qpaintengine_raster_p.h b/src/gui/painting/qpaintengine_raster_p.h
index 59213220a6..d0b82b3a93 100644
--- a/src/gui/painting/qpaintengine_raster_p.h
+++ b/src/gui/painting/qpaintengine_raster_p.h
@@ -225,7 +225,7 @@ public:
 #endif
 
     QRasterBuffer *rasterBuffer();
-    void alphaPenBlt(const void* src, int bpl, int depth, int rx,int ry,int w,int h);
+    void alphaPenBlt(const void* src, int bpl, int depth, int rx,int ry,int w,int h, bool useGammaCorrection);
 
     Type type() const Q_DECL_OVERRIDE { return Raster; }
 
diff --git a/src/gui/text/qfontengine.cpp b/src/gui/text/qfontengine.cpp
index 0b2972f189..8d8ca1ba2c 100644
--- a/src/gui/text/qfontengine.cpp
+++ b/src/gui/text/qfontengine.cpp
@@ -445,6 +445,11 @@ bool QFontEngine::supportsTransformation(const QTransform &transform) const
     return transform.type() < QTransform::TxProject;
 }
 
+bool QFontEngine::expectsGammaCorrectedBlending() const
+{
+    return true;
+}
+
 void QFontEngine::getGlyphPositions(const QGlyphLayout &glyphs, const QTransform &matrix, QTextItem::RenderFlags flags,
                                     QVarLengthArray<glyph_t> &glyphs_out, QVarLengthArray<QFixedPoint> &positions)
 {
diff --git a/src/gui/text/qfontengine_ft.cpp b/src/gui/text/qfontengine_ft.cpp
index de6da88245..03e72546eb 100644
--- a/src/gui/text/qfontengine_ft.cpp
+++ b/src/gui/text/qfontengine_ft.cpp
@@ -61,17 +61,19 @@
 #include FT_TRUETYPE_TABLES_H
 #include FT_TYPE1_TABLES_H
 #include FT_GLYPH_H
+#include FT_MODULE_H
 
 #if defined(FT_LCD_FILTER_H)
 #include FT_LCD_FILTER_H
+#define QT_USE_FREETYPE_LCDFILTER
 #endif
 
 #if defined(FT_CONFIG_OPTIONS_H)
 #include FT_CONFIG_OPTIONS_H
 #endif
 
-#if defined(FT_LCD_FILTER_H)
-#define QT_USE_FREETYPE_LCDFILTER
+#if defined(FT_FONT_FORMATS_H)
+#include FT_FONT_FORMATS_H
 #endif
 
 #ifdef QT_LINUXBASE
@@ -151,6 +153,14 @@ QtFreetypeData *qt_getFreetypeData()
     QtFreetypeData *&freetypeData = theFreetypeData()->localData();
     if (!freetypeData)
         freetypeData = new QtFreetypeData;
+    if (!freetypeData->library) {
+        FT_Init_FreeType(&freetypeData->library);
+#if defined(FT_FONT_FORMATS_H)
+        // Freetype defaults to disabling stem-darkening on CFF, we re-enable it.
+        FT_Bool no_darkening = false;
+        FT_Property_Set(freetypeData->library, "cff", "no-stem-darkening", &no_darkening);
+#endif
+    }
     return freetypeData;
 }
 #endif
@@ -158,8 +168,7 @@ QtFreetypeData *qt_getFreetypeData()
 FT_Library qt_getFreetype()
 {
     QtFreetypeData *freetypeData = qt_getFreetypeData();
-    if (!freetypeData->library)
-        FT_Init_FreeType(&freetypeData->library);
+    Q_ASSERT(freetypeData->library);
     return freetypeData->library;
 }
 
@@ -218,8 +227,6 @@ QFreetypeFace *QFreetypeFace::getFace(const QFontEngine::FaceId &face_id,
         return 0;
 
     QtFreetypeData *freetypeData = qt_getFreetypeData();
-    if (!freetypeData->library)
-        FT_Init_FreeType(&freetypeData->library);
 
     QFreetypeFace *freetype = freetypeData->faces.value(face_id, 0);
     if (freetype) {
@@ -687,6 +694,7 @@ QFontEngineFT::QFontEngineFT(const QFontDef &fd)
     cacheEnabled = env.isEmpty() || env.toInt() == 0;
     m_subPixelPositionCount = 4;
     forceAutoHint = false;
+    stemDarkeningDriver = false;
 }
 
 QFontEngineFT::~QFontEngineFT()
@@ -798,6 +806,17 @@ bool QFontEngineFT::init(FaceId faceId, bool antialias, GlyphFormat format,
             }
         }
     }
+#if defined(FT_FONT_FORMATS_H)
+    const char *fmt = FT_Get_Font_Format(face);
+    if (fmt && qstrncmp(fmt, "CFF", 4) == 0) {
+        FT_Bool no_stem_darkening = true;
+        FT_Error err = FT_Property_Get(qt_getFreetype(), "cff", "no-stem-darkening", &no_stem_darkening);
+        if (err == FT_Err_Ok)
+            stemDarkeningDriver = !no_stem_darkening;
+        else
+            stemDarkeningDriver = false;
+    }
+#endif
 
     fontDef.styleName = QString::fromUtf8(face->style_name);
 
@@ -841,6 +860,11 @@ void QFontEngineFT::setDefaultHintStyle(HintStyle style)
     default_hint_style = style;
 }
 
+bool QFontEngineFT::expectsGammaCorrectedBlending() const
+{
+    return stemDarkeningDriver;
+}
+
 int QFontEngineFT::loadFlags(QGlyphSet *set, GlyphFormat format, int flags,
                              bool &hsubpixel, int &vfactor) const
 {
diff --git a/src/gui/text/qfontengine_ft_p.h b/src/gui/text/qfontengine_ft_p.h
index 32357d0076..47f13eb274 100644
--- a/src/gui/text/qfontengine_ft_p.h
+++ b/src/gui/text/qfontengine_ft_p.h
@@ -252,6 +252,7 @@ private:
                                    QPoint *offset) Q_DECL_OVERRIDE;
     bool hasInternalCaching() const Q_DECL_OVERRIDE { return cacheEnabled; }
     void unlockAlphaMapForGlyph() Q_DECL_OVERRIDE;
+    bool expectsGammaCorrectedBlending() const Q_DECL_OVERRIDE;
 
     void removeGlyphFromCache(glyph_t glyph) Q_DECL_OVERRIDE;
     int glyphMargin(QFontEngine::GlyphFormat /* format */) Q_DECL_OVERRIDE { return 0; }
@@ -311,6 +312,7 @@ protected:
     bool embeddedbitmap;
     bool cacheEnabled;
     bool forceAutoHint;
+    bool stemDarkeningDriver;
 
 private:
     friend class QFontEngineFTRawFont;
diff --git a/src/gui/text/qfontengine_p.h b/src/gui/text/qfontengine_p.h
index c0e350f755..514e9424b2 100644
--- a/src/gui/text/qfontengine_p.h
+++ b/src/gui/text/qfontengine_p.h
@@ -254,6 +254,7 @@ public:
     static QByteArray convertToPostscriptFontFamilyName(const QByteArray &fontFamily);
 
     virtual bool hasUnreliableGlyphOutline() const;
+    virtual bool expectsGammaCorrectedBlending() const;
 
     enum HintStyle {
         HintNone,
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
index 1f152a3d32..c8ae342f16 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
@@ -602,6 +602,11 @@ glyph_metrics_t QCoreTextFontEngine::alphaMapBoundingBox(glyph_t glyph, QFixed s
     return br;
 }
 
+bool QCoreTextFontEngine::expectsGammaCorrectedBlending() const
+{
+    // Only works well when font-smoothing is enabled
+    return (glyphFormat == Format_A32) && !(fontDef.styleStrategy & (QFont::NoAntialias | QFont::NoSubpixelAntialias));
+}
 
 QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition, bool aa, const QTransform &matrix)
 {
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h b/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
index d9ffbb5697..0074790e43 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
@@ -110,6 +110,7 @@ public:
     void doKerning(QGlyphLayout *g, ShaperFlags flags) const Q_DECL_OVERRIDE;
 
     bool supportsTransformation(const QTransform &transform) const Q_DECL_OVERRIDE;
+    bool expectsGammaCorrectedBlending() const Q_DECL_OVERRIDE;
 
     QFontEngine *cloneWithSize(qreal pixelSize) const Q_DECL_OVERRIDE;
     Qt::HANDLE handle() const Q_DECL_OVERRIDE;
diff --git a/src/platformsupport/fontdatabases/windows/qwindowsfontdatabase.cpp b/src/platformsupport/fontdatabases/windows/qwindowsfontdatabase.cpp
index a5779fc291..2a5e7006e6 100644
--- a/src/platformsupport/fontdatabases/windows/qwindowsfontdatabase.cpp
+++ b/src/platformsupport/fontdatabases/windows/qwindowsfontdatabase.cpp
@@ -1207,8 +1207,6 @@ QWindowsFontEngineDataPtr sharedFontData()
 }
 #endif // QT_NO_THREAD
 
-extern Q_GUI_EXPORT bool qt_needs_a8_gamma_correction;
-
 QWindowsFontDatabase::QWindowsFontDatabase()
 {
     // Properties accessed by QWin32PrintEngine (Qt Print Support)
@@ -1222,7 +1220,6 @@ QWindowsFontDatabase::QWindowsFontDatabase()
         qCDebug(lcQpaFonts) << __FUNCTION__ << "Clear type: "
             << data->clearTypeEnabled << "gamma: " << data->fontSmoothingGamma;
     }
-    qt_needs_a8_gamma_correction = true;
 }
 
 QWindowsFontDatabase::~QWindowsFontDatabase()
diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index af9ffab8ae..47c85fce18 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -384,9 +384,6 @@ QVariant QXcbIntegration::styleHint(QPlatformIntegration::StyleHint hint) const
     case QPlatformIntegration::PasswordMaskCharacter:
         // TODO using various xcb, gnome or KDE settings
         break; // Not implemented, use defaults
-    case QPlatformIntegration::FontSmoothingGamma:
-        // Match Qt 4.8 text rendering, and rendering of other X11 toolkits.
-        return qreal(1.0);
     case QPlatformIntegration::StartDragDistance: {
         // The default (in QPlatformTheme::defaultThemeHint) is 10 pixels, but
         // on a high-resolution screen it makes sense to increase it.