Prevent repeated and unnecessary font population QCoreTextFontDatabase

The platform font database is populated from QFontDatabase, through the
static initializeDb() function, whenever the font database determines
that the platform database has not been initialized (by checking if the
font database is empty).

There are other clients of QPlatformFontDatabase though, such as QFont,
which uses the platform font database to check for the default family.
The CoreText implementation of determining the default family relies
on data that is computed during font population, and hence does an
internal (self-triggered) populate.

To prevent repeated populates as a result of calling QFont::defaultFamily()
we guard the populate by a similar isEmpty() check as QFontDatabase does,
but to ensure that this check works in the case of an invalidated font
database, we need to propagate the font database invalidation down to
the platform font database.

Change-Id: I8d06c6f6fc5da6353c087335859eaca008c2f6a6
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

2 files changed, 30 insertions, 19 deletions

diff --git a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
index 76506d12e9..f37e7a1db2 100644
--- a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
+++ b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
@@ -199,6 +199,12 @@ void QCoreTextFontDatabase::populateFontDatabase()
     [pool release];
 }
 
+void QCoreTextFontDatabase::invalidate()
+{
+    psNameToFamily.clear();
+    familyNameToPsName.clear();
+}
+
 void QCoreTextFontDatabase::populateFromDescriptor(CTFontDescriptorRef font)
 {
     QString foundryName = QStringLiteral("CoreText");
@@ -389,29 +395,31 @@ QStringList QCoreTextFontDatabase::fallbacksForFamily(const QString &family, QFo
             if (fallbackLists.contains(family))
                 return fallbackLists.value(family);
 
-            if (!familyNameToPsName.contains(family))
+            if (familyNameToPsName.isEmpty())
                 const_cast<QCoreTextFontDatabase*>(this)->populateFontDatabase();
 
-            QCFType<CTFontRef> font = CTFontCreateWithName(QCFString(familyNameToPsName[family]), 12.0, NULL);
-            if (font) {
-                NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
-                NSArray *languages = [defaults stringArrayForKey: @"AppleLanguages"];
-
-                QCFType<CFArrayRef> cascadeList = (CFArrayRef) CTFontCopyDefaultCascadeListForLanguages(font, (CFArrayRef) languages);
-                if (cascadeList) {
-                    QStringList fallbackList;
-                    const int numCascades = CFArrayGetCount(cascadeList);
-                    for (int i = 0; i < numCascades; ++i) {
-                        CTFontDescriptorRef fontFallback = (CTFontDescriptorRef) CFArrayGetValueAtIndex(cascadeList, i);
-                        QCFString fallbackFamilyName = (CFStringRef) CTFontDescriptorCopyLocalizedAttribute(fontFallback, kCTFontFamilyNameAttribute, NULL);
-                        fallbackList.append(QCFString::toQString(fallbackFamilyName));
+            if (familyNameToPsName.contains(family)) {
+                QCFType<CTFontRef> font = CTFontCreateWithName(QCFString(familyNameToPsName[family]), 12.0, NULL);
+                if (font) {
+                    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
+                    NSArray *languages = [defaults stringArrayForKey: @"AppleLanguages"];
+
+                    QCFType<CFArrayRef> cascadeList = (CFArrayRef) CTFontCopyDefaultCascadeListForLanguages(font, (CFArrayRef) languages);
+                    if (cascadeList) {
+                        QStringList fallbackList;
+                        const int numCascades = CFArrayGetCount(cascadeList);
+                        for (int i = 0; i < numCascades; ++i) {
+                            CTFontDescriptorRef fontFallback = (CTFontDescriptorRef) CFArrayGetValueAtIndex(cascadeList, i);
+                            QCFString fallbackFamilyName = (CFStringRef) CTFontDescriptorCopyLocalizedAttribute(fontFallback, kCTFontFamilyNameAttribute, NULL);
+                            fallbackList.append(QCFString::toQString(fallbackFamilyName));
+                        }
+                        fallbackLists[family] = fallbackList;
                     }
-                    fallbackLists[family] = fallbackList;
                 }
-            }
 
-            if (fallbackLists.contains(family))
-                return fallbackLists.value(family);
+                if (fallbackLists.contains(family))
+                    return fallbackLists.value(family);
+            }
         }
 #endif
     }
@@ -425,7 +433,8 @@ QStringList QCoreTextFontDatabase::fallbacksForFamily(const QString &family, QFo
     if (!didPopulateStyleFallbacks) {
 #if defined(Q_OS_MACX)
         // Ensure we have the psNameToFamily mapping set up
-        const_cast<QCoreTextFontDatabase*>(this)->populateFontDatabase();
+        if (psNameToFamily.isEmpty())
+            const_cast<QCoreTextFontDatabase*>(this)->populateFontDatabase();
 
         NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
         NSArray *languages = [defaults stringArrayForKey: @"AppleLanguages"];
diff --git a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase_p.h b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase_p.h
index 1560d36644..5b2fc2ed7e 100644
--- a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase_p.h
+++ b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase_p.h
@@ -72,6 +72,8 @@ public:
     QCoreTextFontDatabase();
     ~QCoreTextFontDatabase();
     void populateFontDatabase();
+    void invalidate() Q_DECL_OVERRIDE;
+
     QFontEngine *fontEngine(const QFontDef &fontDef, void *handle);
     QFontEngine *fontEngine(const QByteArray &fontData, qreal pixelSize, QFont::HintingPreference hintingPreference);
     QStringList fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const;