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>

3 files changed, 17 insertions, 6 deletions

diff --git a/src/gui/text/qfontengine.cpp b/src/gui/text/qfontengine.cpp
index eb7e416dd1..5506d88f02 100644
--- a/src/gui/text/qfontengine.cpp
+++ b/src/gui/text/qfontengine.cpp
@@ -899,7 +899,7 @@ QImage QFontEngine::alphaRGBMapForGlyph(glyph_t glyph, QFixed /*subPixelPosition
     return rgbMask;
 }
 
-QImage QFontEngine::bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform&)
+QImage QFontEngine::bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform&, const QColor &)
 {
     Q_UNUSED(subPixelPosition);
 
@@ -1075,7 +1075,10 @@ void QFontEngine::setGlyphCache(const void *context, QFontEngineGlyphCache *cach
 
 }
 
-QFontEngineGlyphCache *QFontEngine::glyphCache(const void *context, GlyphFormat format, const QTransform &transform) const
+QFontEngineGlyphCache *QFontEngine::glyphCache(const void *context,
+                                               GlyphFormat format,
+                                               const QTransform &transform,
+                                               const QColor &color) const
 {
     const QHash<const void*, GlyphCaches>::const_iterator caches = m_glyphCaches.constFind(context);
     if (caches == m_glyphCaches.cend())
@@ -1083,8 +1086,11 @@ QFontEngineGlyphCache *QFontEngine::glyphCache(const void *context, GlyphFormat
 
     for (GlyphCaches::const_iterator it = caches->begin(), end = caches->end(); it != end; ++it) {
         QFontEngineGlyphCache *cache = it->cache.data();
-        if (format == cache->glyphFormat() && qtransform_equals_no_translate(cache->m_transform, transform))
+        if (format == cache->glyphFormat()
+                && (format != Format_ARGB || color == cache->color())
+                && qtransform_equals_no_translate(cache->m_transform, transform)) {
             return cache;
+        }
     }
 
     return nullptr;
diff --git a/src/gui/text/qfontengine_p.h b/src/gui/text/qfontengine_p.h
index 708c79c2ae..682395ece6 100644
--- a/src/gui/text/qfontengine_p.h
+++ b/src/gui/text/qfontengine_p.h
@@ -190,7 +190,7 @@ public:
     virtual QImage alphaMapForGlyph(glyph_t, const QTransform &t);
     virtual QImage alphaMapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t);
     virtual QImage alphaRGBMapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t);
-    virtual QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t);
+    virtual QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t, const QColor &color = QColor());
     virtual QImage *lockedAlphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition,
                                            GlyphFormat neededFormat,
                                            const QTransform &t = QTransform(),
@@ -252,7 +252,7 @@ public:
 
     void clearGlyphCache(const void *key);
     void setGlyphCache(const void *key, QFontEngineGlyphCache *data);
-    QFontEngineGlyphCache *glyphCache(const void *key, GlyphFormat format, const QTransform &transform) const;
+    QFontEngineGlyphCache *glyphCache(const void *key, GlyphFormat format, const QTransform &transform, const QColor &color = QColor()) const;
 
     static const uchar *getCMap(const uchar *table, uint tableSize, bool *isSymbolFont, int *cmapSize);
     static quint32 getTrueTypeGlyphIndex(const uchar *cmap, int cmapSize, uint unicode);
diff --git a/src/gui/text/qfontengineglyphcache_p.h b/src/gui/text/qfontengineglyphcache_p.h
index fd5db1ecf5..532be10a83 100644
--- a/src/gui/text/qfontengineglyphcache_p.h
+++ b/src/gui/text/qfontengineglyphcache_p.h
@@ -65,7 +65,10 @@ QT_BEGIN_NAMESPACE
 class Q_GUI_EXPORT QFontEngineGlyphCache: public QSharedData
 {
 public:
-    QFontEngineGlyphCache(QFontEngine::GlyphFormat format, const QTransform &matrix) : m_format(format), m_transform(matrix)
+    QFontEngineGlyphCache(QFontEngine::GlyphFormat format, const QTransform &matrix, const QColor &color = QColor())
+        : m_format(format)
+        , m_transform(matrix)
+        , m_color(color)
     {
         Q_ASSERT(m_format != QFontEngine::Format_None);
     }
@@ -74,9 +77,11 @@ public:
 
     QFontEngine::GlyphFormat glyphFormat() const { return m_format; }
     const QTransform &transform() const { return m_transform; }
+    const QColor &color() const { return m_color; }
 
     QFontEngine::GlyphFormat m_format;
     QTransform m_transform;
+    QColor m_color;
 };
 typedef QHash<void *, QList<QFontEngineGlyphCache *> > GlyphPointerHash;
 typedef QHash<int, QList<QFontEngineGlyphCache *> > GlyphIntHash;