QFontEngine: Add handle() function

Both QFont::handle() and QFont::freetypeFace() used to
be available in Qt 4 but were removed in Qt 5. There's
currently no API to get access to the native font handle,
which the font engine holds in a way or another.

Similar to the way it was in Qt 4, the actual handle type
depends on the font engine currently in use. The types map
as follows:

     Font Engine      Native Handle
    ------------------------------------
     DirectWrite      IDWriteFontFace *
     Freetype         FT_Face
     Mac              CTFontRef
     Win              HFONT

All other font engines return a null handle.

Change-Id: I3bea8259ac1378fd24079723aa6603bf9e74834c
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

src/gui/text/qfontengine.cpp

@@ -1229,6 +1229,11 @@ int QFontEngine::glyphCount() const
     return count;
 }
 
+Qt::HANDLE QFontEngine::handle() const
+{
+    return Q_NULLPTR;
+}
+
 const uchar *QFontEngine::getCMap(const uchar *table, uint tableSize, bool *isSymbolFont, int *cmapSize)
 {
     const uchar *header = table;

src/gui/text/qfontengine_ft.cpp

@@ -2005,6 +2005,11 @@ QFontEngine *QFontEngineFT::cloneWithSize(qreal pixelSize) const
     }
 }
 
+Qt::HANDLE QFontEngineFT::handle() const
+{
+    return non_locked_face();
+}
+
 QT_END_NAMESPACE
 
 #endif // QT_NO_FREETYPE

src/gui/text/qfontengine_ft_p.h

@@ -283,6 +283,7 @@ private:
     void setDefaultHintStyle(HintStyle style) Q_DECL_OVERRIDE;
 
     QFontEngine *cloneWithSize(qreal pixelSize) const Q_DECL_OVERRIDE;
+    Qt::HANDLE handle() const Q_DECL_OVERRIDE;
     bool initFromFontEngine(const QFontEngineFT *fontEngine);
 
     HintStyle defaultHintStyle() const { return default_hint_style; }

src/gui/text/qfontengine_p.h

@@ -229,6 +229,8 @@ public:
 
     virtual QFontEngine *cloneWithSize(qreal /*pixelSize*/) const { return 0; }
 
+    virtual Qt::HANDLE handle() const;
+
     void *harfbuzzFont() const;
     void *harfbuzzFace() const;
     bool supportsScript(QChar::Script script) const;

src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm

@@ -738,6 +738,11 @@ QFontEngine *QCoreTextFontEngine::cloneWithSize(qreal pixelSize) const
     return new QCoreTextFontEngine(cgFont, newFontDef);
 }
 
+Qt::HANDLE QCoreTextFontEngine::handle() const
+{
+    return (Qt::HANDLE)ctfont;
+}
+
 bool QCoreTextFontEngine::supportsTransformation(const QTransform &transform) const
 {
     if (transform.type() < QTransform::TxScale)

src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h

@@ -101,6 +101,7 @@ public:
     bool supportsTransformation(const QTransform &transform) const Q_DECL_OVERRIDE;
 
     QFontEngine *cloneWithSize(qreal pixelSize) const Q_DECL_OVERRIDE;
+    Qt::HANDLE handle() const Q_DECL_OVERRIDE;
     int glyphMargin(QFontEngine::GlyphFormat format) Q_DECL_OVERRIDE { Q_UNUSED(format); return 0; }
 
     QFontEngine::Properties properties() const Q_DECL_OVERRIDE;

src/plugins/platforms/windows/qwindowsfontengine.cpp

@@ -1256,6 +1256,11 @@ QFontEngine *QWindowsFontEngine::cloneWithSize(qreal pixelSize) const
     return fontEngine;
 }
 
+Qt::HANDLE QWindowsFontEngine::handle() const
+{
+    return hfont;
+}
+
 void QWindowsFontEngine::initFontInfo(const QFontDef &request,
                                       int dpi)
 {

src/plugins/platforms/windows/qwindowsfontengine.h

@@ -108,6 +108,7 @@ public:
     glyph_metrics_t alphaMapBoundingBox(glyph_t glyph, QFixed, const QTransform &matrix, GlyphFormat) Q_DECL_OVERRIDE;
 
     QFontEngine *cloneWithSize(qreal pixelSize) const Q_DECL_OVERRIDE;
+    Qt::HANDLE handle() const Q_DECL_OVERRIDE;
     bool supportsTransformation(const QTransform &transform) const Q_DECL_OVERRIDE;
 
 #ifndef Q_CC_MINGW

src/plugins/platforms/windows/qwindowsfontenginedirectwrite.cpp

@@ -639,6 +639,11 @@ QFontEngine *QWindowsFontEngineDirectWrite::cloneWithSize(qreal pixelSize) const
     return fontEngine;
 }
 
+Qt::HANDLE QWindowsFontEngineDirectWrite::handle() const
+{
+    return m_directWriteFontFace;
+}
+
 void QWindowsFontEngineDirectWrite::initFontInfo(const QFontDef &request,
                                                  int dpi)
 {

src/plugins/platforms/windows/qwindowsfontenginedirectwrite.h

@@ -92,6 +92,7 @@ public:
     QImage alphaRGBMapForGlyph(glyph_t t, QFixed subPixelPosition, const QTransform &xform) Q_DECL_OVERRIDE;
 
     QFontEngine *cloneWithSize(qreal pixelSize) const Q_DECL_OVERRIDE;
+    Qt::HANDLE handle() const Q_DECL_OVERRIDE;
 
     const QSharedPointer<QWindowsFontEngineData> &fontEngineData() const { return m_fontEngineData; }