Support pen color with color fonts

Color fonts may also contain regular alphabet characters that
should be rendered with the current pen. In Qt, however, these
characters were drawn into the cache with a default pen color
of black.

Since all characters in a font is currently backed by the same cache,
and it would require a lot of plumbing to get around this, a step
in the right direction is to include the current pen color in the
cache as long as it is an RGB cache. This means that drawing
text with the color font with different pen colors will create
different caches.

There is no API to select font color on Freetype currently, but
this problem has also not been observed there, as the fonts
in question, with both regular and color glyphs, are not being
detected as color fonts (so the text color will be correct).
So Freetype will be left out for now.

[ChangeLog][QtGui][Text] Fixed bug where regular text rendered
with a color font would always display in black.

Task-number: QTBUG-55096
Task-number: QTBUG-74761
Change-Id: Icc7dbf73241db1e7cc6a0de18c2de927aeecf713
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

6 files changed, 45 insertions, 21 deletions

diff --git a/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp b/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp
index 8d6620a55f..ef80d68bfe 100644
--- a/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp
+++ b/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp
@@ -2105,8 +2105,10 @@ QImage QFontEngineFT::alphaRGBMapForGlyph(glyph_t g, QFixed subPixelPosition, co
     return QFontEngine::alphaRGBMapForGlyph(g, subPixelPosition, t);
 }
 
-QImage QFontEngineFT::bitmapForGlyph(glyph_t g, QFixed subPixelPosition, const QTransform &t)
+QImage QFontEngineFT::bitmapForGlyph(glyph_t g, QFixed subPixelPosition, const QTransform &t, const QColor &color)
 {
+    Q_UNUSED(color);
+
     Glyph *glyph = loadGlyphFor(g, subPixelPosition, defaultFormat, t);
     if (glyph == nullptr)
         return QImage();
diff --git a/src/platformsupport/fontdatabases/freetype/qfontengine_ft_p.h b/src/platformsupport/fontdatabases/freetype/qfontengine_ft_p.h
index d498b0ac8b..109bae86e9 100644
--- a/src/platformsupport/fontdatabases/freetype/qfontengine_ft_p.h
+++ b/src/platformsupport/fontdatabases/freetype/qfontengine_ft_p.h
@@ -236,7 +236,7 @@ private:
     QImage alphaMapForGlyph(glyph_t, QFixed) override;
     QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t) override;
     QImage alphaRGBMapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t) override;
-    QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t) override;
+    QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t, const QColor &color) override;
     glyph_metrics_t alphaMapBoundingBox(glyph_t glyph,
                                         QFixed subPixelPosition,
                                         const QTransform &matrix,
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
index 25e7c6df72..072dd1a28a 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
@@ -747,7 +747,7 @@ qreal QCoreTextFontEngine::fontSmoothingGamma()
     return 2.0;
 }
 
-QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &matrix)
+QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &matrix, const QColor &color)
 {
     glyph_metrics_t br = alphaMapBoundingBox(glyph, subPixelPosition, matrix, glyphFormat);
 
@@ -827,6 +827,8 @@ QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition
             CTFontDrawGlyphs(ctfont, &cgGlyph, &CGPointZero, 1, ctx);
         }
     } else {
+        CGContextSetRGBFillColor(ctx, color.redF(), color.greenF(), color.blueF(), color.alphaF());
+
         // CGContextSetTextMatrix does not work with color glyphs, so we use
         // the CTM instead. This means we must translate the CTM as well, to
         // set the glyph position, instead of using CGContextSetTextPosition.
@@ -884,12 +886,12 @@ QImage QCoreTextFontEngine::alphaRGBMapForGlyph(glyph_t glyph, QFixed subPixelPo
     return imageForGlyph(glyph, subPixelPosition, x);
 }
 
-QImage QCoreTextFontEngine::bitmapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t)
+QImage QCoreTextFontEngine::bitmapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t, const QColor &color)
 {
     if (t.type() > QTransform::TxScale)
-        return QFontEngine::bitmapForGlyph(glyph, subPixelPosition, t);
+        return QFontEngine::bitmapForGlyph(glyph, subPixelPosition, t, color);
 
-    return imageForGlyph(glyph, subPixelPosition, t);
+    return imageForGlyph(glyph, subPixelPosition, t, color);
 }
 
 void QCoreTextFontEngine::recalcAdvances(QGlyphLayout *glyphs, QFontEngine::ShaperFlags flags) const
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h b/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
index 4064507058..51d839688d 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
@@ -110,7 +110,7 @@ public:
     QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t) override;
     QImage alphaRGBMapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t) override;
     glyph_metrics_t alphaMapBoundingBox(glyph_t glyph, QFixed, const QTransform &matrix, GlyphFormat) override;
-    QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t) override;
+    QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t, const QColor &color) override;
     QFixed emSquareSize() const override;
     void doKerning(QGlyphLayout *g, ShaperFlags flags) const override;
 
@@ -137,7 +137,7 @@ public:
 protected:
     QCoreTextFontEngine(const QFontDef &def);
     void init();
-    QImage imageForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &m);
+    QImage imageForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &m, const QColor &color = QColor());
     void loadAdvancesForGlyphs(QVarLengthArray<CGGlyph> &cgGlyphs, QGlyphLayout *glyphs) const;
     bool hasColorGlyphs() const;
     bool shouldAntialias() const;
diff --git a/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp b/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp
index 57c41938bc..a7ee65f4b8 100644
--- a/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp
+++ b/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp
@@ -650,7 +650,8 @@ bool QWindowsFontEngineDirectWrite::supportsSubPixelPositions() const
 QImage QWindowsFontEngineDirectWrite::imageForGlyph(glyph_t t,
                                              QFixed subPixelPosition,
                                              int margin,
-                                             const QTransform &originalTransform)
+                                             const QTransform &originalTransform,
+                                             const QColor &color)
 {
     UINT16 glyphIndex = t;
     FLOAT glyphAdvance = 0;
@@ -735,6 +736,7 @@ QImage QWindowsFontEngineDirectWrite::imageForGlyph(glyph_t t,
 
 #if defined(QT_USE_DIRECTWRITE2)
         BOOL ok = true;
+
         if (SUCCEEDED(hr)) {
             while (SUCCEEDED(hr) && ok) {
                 const DWRITE_COLOR_GLYPH_RUN *colorGlyphRun = 0;
@@ -759,10 +761,18 @@ QImage QWindowsFontEngineDirectWrite::imageForGlyph(glyph_t t,
                     break;
                 }
 
-                float r = qBound(0.0f, colorGlyphRun->runColor.r, 1.0f);
-                float g = qBound(0.0f, colorGlyphRun->runColor.g, 1.0f);
-                float b = qBound(0.0f, colorGlyphRun->runColor.b, 1.0f);
-                float a = qBound(0.0f, colorGlyphRun->runColor.a, 1.0f);
+                float r, g, b, a;
+                if (colorGlyphRun->paletteIndex == 0xFFFF) {
+                    r = float(color.redF());
+                    g = float(color.greenF());
+                    b = float(color.blueF());
+                    a = float(color.alphaF());
+                } else {
+                    r = qBound(0.0f, colorGlyphRun->runColor.r, 1.0f);
+                    g = qBound(0.0f, colorGlyphRun->runColor.g, 1.0f);
+                    b = qBound(0.0f, colorGlyphRun->runColor.b, 1.0f);
+                    a = qBound(0.0f, colorGlyphRun->runColor.a, 1.0f);
+                }
 
                 if (!qFuzzyIsNull(a)) {
                     renderGlyphRun(&image,
@@ -784,11 +794,21 @@ QImage QWindowsFontEngineDirectWrite::imageForGlyph(glyph_t t,
         } else
 #endif
         {
+            float r, g, b, a;
+            if (glyphFormat == QFontEngine::Format_ARGB) {
+                r = float(color.redF());
+                g = float(color.greenF());
+                b = float(color.blueF());
+                a = float(color.alphaF());
+            } else {
+                r = g = b = a = 0.0;
+            }
+
             renderGlyphRun(&image,
-                           0.0,
-                           0.0,
-                           0.0,
-                           1.0,
+                           r,
+                           g,
+                           b,
+                           a,
                            glyphAnalysis,
                            boundingRect);
         }
@@ -1001,9 +1021,9 @@ glyph_metrics_t QWindowsFontEngineDirectWrite::alphaMapBoundingBox(glyph_t glyph
     }
 }
 
-QImage QWindowsFontEngineDirectWrite::bitmapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t)
+QImage QWindowsFontEngineDirectWrite::bitmapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t, const QColor &color)
 {
-    return imageForGlyph(glyph, subPixelPosition, glyphMargin(QFontEngine::Format_A32), t);
+    return imageForGlyph(glyph, subPixelPosition, glyphMargin(QFontEngine::Format_A32), t, color);
 }
 
 QT_END_NAMESPACE
diff --git a/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite_p.h b/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite_p.h
index 9326f5aece..9e13474a04 100644
--- a/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite_p.h
+++ b/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite_p.h
@@ -112,7 +112,7 @@ public:
     QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition) override;
     QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t) override;
     QImage alphaRGBMapForGlyph(glyph_t t, QFixed subPixelPosition, const QTransform &xform) override;
-    QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t) override;
+    QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t, const QColor &color) override;
 
     QFontEngine *cloneWithSize(qreal pixelSize) const override;
     Qt::HANDLE handle() const override;
@@ -126,7 +126,7 @@ public:
     void setUniqueFamilyName(const QString &newName) { m_uniqueFamilyName = newName; }
 
 private:
-    QImage imageForGlyph(glyph_t t, QFixed subPixelPosition, int margin, const QTransform &xform);
+    QImage imageForGlyph(glyph_t t, QFixed subPixelPosition, int margin, const QTransform &xform, const QColor &color = QColor());
     void collectMetrics();
     void renderGlyphRun(QImage *destination, float r, float g, float b, float a, IDWriteGlyphRunAnalysis *glyphAnalysis, const QRect &boundingRect);
     static QString filenameFromFontFile(IDWriteFontFile *fontFile);