Add virtual function to QFontEngine report if outlines are reliable

GetGlyphOutline fails for ttf fonts with embedded bitmaps. This results in
distancefield rendering not rendering glyphs (for the failed paths). We
need to fall back to texture rendering if this is the case.

Change-Id: Ibdf7dc5c1d34f513c436f88fabbdcc4089bb6fef
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

src/gui/text/qfontengine.cpp

@@ -1335,6 +1335,15 @@ QByteArray QFontEngine::convertToPostscriptFontFamilyName(const QByteArray &fami
     return f;
 }
 
+/**
+ * Some font engines like the windows font engine
+ * can not reliable create outline paths
+ */
+bool QFontEngine::hasUnreliableGlyphOutline() const
+{
+    return false;
+}
+
 QFixed QFontEngine::lastRightBearing(const QGlyphLayout &glyphs, bool round)
 {
     if (glyphs.numGlyphs >= 1) {

src/gui/text/qfontengine_p.h

@@ -251,6 +251,8 @@ public:
 
     static QByteArray convertToPostscriptFontFamilyName(const QByteArray &fontFamily);
 
+    virtual bool hasUnreliableGlyphOutline() const;
+
     enum HintStyle {
         HintNone,
         HintLight,

src/plugins/platforms/windows/qwindowsfontengine.cpp

@@ -169,6 +169,20 @@ bool QWindowsFontEngine::hasCMapTable() const
     return GetFontData(hdc, MAKE_TAG('c', 'm', 'a', 'p'), 0, 0, 0) != GDI_ERROR;
 }
 
+bool QWindowsFontEngine::hasGlyfTable() const
+{
+    HDC hdc = m_fontEngineData->hdc;
+    SelectObject(hdc, hfont);
+    return GetFontData(hdc, MAKE_TAG('g', 'l', 'y', 'f'), 0, 0, 0) != GDI_ERROR;
+}
+
+bool QWindowsFontEngine::hasEbdtTable() const
+{
+    HDC hdc = m_fontEngineData->hdc;
+    SelectObject(hdc, hfont);
+    return GetFontData(hdc, MAKE_TAG('E', 'B', 'D', 'T'), 0, 0, 0) != GDI_ERROR;
+}
+
 void QWindowsFontEngine::getCMap()
 {
     ttf = (bool)(tm.tmPitchAndFamily & TMPF_TRUETYPE) || hasCMapTable();
@@ -308,6 +322,8 @@ QWindowsFontEngine::QWindowsFontEngine(const QString &name,
     userData.insert(QStringLiteral("hFont"), QVariant::fromValue(hfont));
     userData.insert(QStringLiteral("trueType"), QVariant(bool(ttf)));
     setUserData(userData);
+
+    hasUnreliableOutline = hasGlyfTable() && hasEbdtTable();
 }
 
 QWindowsFontEngine::~QWindowsFontEngine()
@@ -662,6 +678,11 @@ void QWindowsFontEngine::getGlyphBearings(glyph_t glyph, qreal *leftBearing, qre
 }
 #endif // Q_CC_MINGW
 
+bool QWindowsFontEngine::hasUnreliableGlyphOutline() const
+{
+    return hasUnreliableOutline;
+}
+
 qreal QWindowsFontEngine::minLeftBearing() const
 {
     if (lbearing == SHRT_MIN)

src/plugins/platforms/windows/qwindowsfontengine.h

@@ -122,6 +122,8 @@ public:
     virtual void getGlyphBearings(glyph_t glyph, qreal *leftBearing = 0, qreal *rightBearing = 0);
 #endif
 
+    bool hasUnreliableGlyphOutline() const Q_DECL_OVERRIDE;
+
     int getGlyphIndexes(const QChar *ch, int numChars, QGlyphLayout *glyphs) const;
     void getCMap();
 
@@ -136,6 +138,8 @@ private:
                                       QImage::Format mask_format);
     bool hasCFFTable() const;
     bool hasCMapTable() const;
+    bool hasGlyfTable() const;
+    bool hasEbdtTable() const;
 
     const QSharedPointer<QWindowsFontEngineData> m_fontEngineData;
 
@@ -146,6 +150,7 @@ private:
     uint        stockFont  : 1;
     uint        ttf        : 1;
     uint        hasOutline : 1;
+    uint        hasUnreliableOutline : 1;
     uint        cffTable   : 1;
     TEXTMETRIC  tm;
     int         lw;