2 files changed, 19 insertions, 9 deletions
diff --git a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
index 6347d4d231..237e8a89a5 100644
--- a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
+++ b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
@@ -416,7 +416,19 @@ extern CGAffineTransform qt_transform_from_fontdef(const QFontDef &fontDef);
 template <>
 QFontEngine *QCoreTextFontDatabaseEngineFactory<QCoreTextFontEngine>::fontEngine(const QFontDef &fontDef, void *usrPtr)
 {
-    CTFontDescriptorRef descriptor = static_cast<CTFontDescriptorRef>(usrPtr);
+    QCFType<CTFontDescriptorRef> descriptor = QCFType<CTFontDescriptorRef>::constructFromGet(
+        static_cast<CTFontDescriptorRef>(usrPtr));
+
+    // CoreText will sometimes invalidate information in font descriptors that refer
+    // to system fonts in certain function calls or application states. While the descriptor
+    // looks the same from the outside, some internal plumbing is different, causing the results
+    // of creating CTFonts from those descriptors unreliable. The work-around for this
+    // is to copy the attributes of those descriptors each time we make a new CTFont
+    // from them instead of referring to the original, as that may trigger the CoreText bug.
+    if (m_systemFontDescriptors.contains(descriptor)) {
+        QCFType<CFDictionaryRef> attributes = CTFontDescriptorCopyAttributes(descriptor);
+        descriptor = CTFontDescriptorCreateWithAttributes(attributes);
+    }
 
     // Since we do not pass in the destination DPI to CoreText when making
     // the font, we need to pass in a point size which is scaled to include
@@ -427,14 +439,10 @@ QFontEngine *QCoreTextFontDatabaseEngineFactory<QCoreTextFontEngine>::fontEngine
     qreal scaledPointSize = fontDef.pixelSize;
 
     CGAffineTransform matrix = qt_transform_from_fontdef(fontDef);
-    CTFontRef font = CTFontCreateWithFontDescriptor(descriptor, scaledPointSize, &matrix);
-    if (font) {
-        QFontEngine *engine = new QCoreTextFontEngine(font, fontDef);
-        CFRelease(font);
-        return engine;
-    }
+    if (QCFType<CTFontRef> font = CTFontCreateWithFontDescriptor(descriptor, scaledPointSize, &matrix))
+        return new QCoreTextFontEngine(font, fontDef);
 
-    return NULL;
+    return nullptr;
 }
 
 #ifndef QT_NO_FREETYPE
diff --git a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase_p.h b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase_p.h
index 2b4c4e3ceb..7e41e50a04 100644
--- a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase_p.h
+++ b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase_p.h
@@ -87,12 +87,14 @@ public:
     QFont *themeFont(QPlatformTheme::Font) const;
     const QHash<QPlatformTheme::Font, QFont *> &themeFonts() const;
 
+protected:
+    mutable QSet<CTFontDescriptorRef> m_systemFontDescriptors;
+
 private:
     void populateFromDescriptor(CTFontDescriptorRef font, const QString &familyName = QString());
 
     mutable QString defaultFontName;
 
-    mutable QSet<CTFontDescriptorRef> m_systemFontDescriptors;
     mutable QHash<QPlatformTheme::Font, QFont *> m_themeFonts;
     bool m_hasPopulatedAliases;
 };