macOS: Prevent leaking font data when creating QRawFont from QByteArrays

CTFontCreateWithGraphicsFont has a bug causing it to never release the
graphics font, which cascades down to the data provider never being
released and releaseFontData never being called.

Instead of relying on a callback to release the byte array font data,
we attach the font data to the engine's lifetime. Note that we are
still leaking the CoreFoundation types.

Change-Id: I6eda4212638ccc9439b90e004222272d204c707a
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

1 files changed, 37 insertions, 0 deletions

diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
index c8ae342f16..49a6049c4b 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
@@ -177,6 +177,43 @@ CGAffineTransform qt_transform_from_fontdef(const QFontDef &fontDef)
     return transform;
 }
 
+// Keeps font data alive until engine is disposed
+class QCoreTextRawFontEngine : public QCoreTextFontEngine
+{
+public:
+    QCoreTextRawFontEngine(CGFontRef font, const QFontDef &def, const QByteArray &fontData)
+        : QCoreTextFontEngine(font, def)
+        , m_fontData(fontData)
+    {}
+    QByteArray m_fontData;
+};
+
+QCoreTextFontEngine *QCoreTextFontEngine::create(const QByteArray &fontData, qreal pixelSize, QFont::HintingPreference hintingPreference)
+{
+    Q_UNUSED(hintingPreference);
+
+    QCFType<CFDataRef> fontDataReference = fontData.toRawCFData();
+    QCFType<CGDataProviderRef> dataProvider = CGDataProviderCreateWithCFData(fontDataReference);
+
+    // Note: CTFontCreateWithGraphicsFont (which we call from the  QCoreTextFontEngine
+    // constructor) has a bug causing it to retain the CGFontRef but never release it.
+    // The result is that we are leaking the CGFont, CGDataProvider, and CGData, but
+    // as the CGData is created from the raw QByteArray data, which we deref in the
+    // subclass above during destruction, we're at least not leaking the font data,
+    // (unless CoreText copies it internally). http://stackoverflow.com/questions/40805382/
+    QCFType<CGFontRef> cgFont = CGFontCreateWithDataProvider(dataProvider);
+
+    if (!cgFont) {
+        qWarning("QCoreTextFontEngine::create: CGFontCreateWithDataProvider failed");
+        return nullptr;
+    }
+
+    QFontDef def;
+    def.pixelSize = pixelSize;
+    def.pointSize = pixelSize * 72.0 / qt_defaultDpi();
+    return new QCoreTextRawFontEngine(cgFont, def, fontData);
+}
+
 QCoreTextFontEngine::QCoreTextFontEngine(CTFontRef font, const QFontDef &def)
     : QFontEngine(Mac)
 {