Default implementation for QPlatformFontDatabase::fallbacksForFamily()

...mainly for platforms that do not provide a native/unified way
to obtain system-defined font fallbacks list
(ie !CoreText && !FontConfig).

Change-Id: I23c5589d79ddecb6311ccc52ec8b29977f06d408
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

src/gui/text/qfontdatabase.cpp

@@ -756,6 +756,46 @@ QString qt_resolveFontFamilyAlias(const QString &alias)
     return alias;
 }
 
+QStringList QPlatformFontDatabase::fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const
+{
+    Q_UNUSED(family);
+    Q_UNUSED(styleHint);
+
+    QStringList retList;
+
+    size_t writingSystem = std::find(scriptForWritingSystem,
+                                     scriptForWritingSystem + QFontDatabase::WritingSystemsCount,
+                                     script) - scriptForWritingSystem;
+    if (writingSystem >= QFontDatabase::WritingSystemsCount)
+        writingSystem = QFontDatabase::Any;
+
+    QFontDatabasePrivate *db = privateDb();
+    for (int i = 0; i < db->count; ++i) {
+        QtFontFamily *f = db->families[i];
+
+        f->ensurePopulated();
+
+        if (writingSystem > QFontDatabase::Any && f->writingSystems[writingSystem] != QtFontFamily::Supported)
+            continue;
+
+        for (int j = 0; j < f->count; ++j) {
+            QtFontFoundry *foundry = f->foundries[j];
+
+            for (int k = 0; k < foundry->count; ++k) {
+                if (style == foundry->styles[k]->key.style) {
+                    if (foundry->name.isEmpty())
+                        retList.append(f->name);
+                    else
+                        retList.append(f->name + QLatin1String(" [") + foundry->name + QLatin1Char(']'));
+                    break;
+                }
+            }
+        }
+    }
+
+    return retList;
+}
+
 QStringList qt_fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script)
 {
     // make sure that the db has all fallback families

src/gui/text/qplatformfontdatabase.cpp

@@ -343,17 +343,15 @@ QFontEngine *QPlatformFontDatabase::fontEngine(const QByteArray &fontData, qreal
 }
 
 /*!
+    \fn QStringList QPlatformFontDatabase::fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const
+
     Returns a list of alternative fonts for the specified \a family and
     \a style and \a script using the \a styleHint given.
+
+    Default implementation returns a list of fonts for which \a style and \a script support
+    has been reported during the font database population.
 */
-QStringList QPlatformFontDatabase::fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const
+// implemented in qfontdatabase.cpp
-{
-    Q_UNUSED(family);
-    Q_UNUSED(style);
-    Q_UNUSED(styleHint);
-    Q_UNUSED(script);
-    return QStringList();
-}
 
 /*!
     Adds an application font described by the font contained supplied \a fontData

src/platformsupport/fontdatabases/basic/qbasicfontdatabase.cpp

@@ -176,15 +176,6 @@ QFontEngine *QBasicFontDatabase::fontEngine(const QByteArray &fontData, qreal pi
     return fe;
 }
 
-QStringList QBasicFontDatabase::fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const
-{
-    Q_UNUSED(family);
-    Q_UNUSED(style);
-    Q_UNUSED(script);
-    Q_UNUSED(styleHint);
-    return QStringList();
-}
-
 QStringList QBasicFontDatabase::addApplicationFont(const QByteArray &fontData, const QString &fileName)
 {
     return addTTFile(fontData,fileName.toLocal8Bit());

src/platformsupport/fontdatabases/basic/qbasicfontdatabase_p.h

@@ -63,7 +63,6 @@ public:
     void populateFontDatabase() Q_DECL_OVERRIDE;
     QFontEngine *fontEngine(const QFontDef &fontDef, void *handle) Q_DECL_OVERRIDE;
     QFontEngine *fontEngine(const QByteArray &fontData, qreal pixelSize, QFont::HintingPreference hintingPreference) Q_DECL_OVERRIDE;
-    QStringList fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const Q_DECL_OVERRIDE;
     QStringList addApplicationFont(const QByteArray &fontData, const QString &fileName) Q_DECL_OVERRIDE;
     void releaseHandle(void *handle) Q_DECL_OVERRIDE;
 

src/plugins/platforms/android/qandroidplatformfontdatabase.cpp

@@ -55,16 +55,7 @@ void QAndroidPlatformFontDatabase::populateFontDatabase()
     QList<QFileInfo> entries = dir.entryInfoList(QStringList() << QStringLiteral("*.ttf") << QStringLiteral("*.otf"), QDir::Files);
     for (int i = 0; i < int(entries.count()); ++i) {
         const QByteArray file = QFile::encodeName(entries.at(i).absoluteFilePath());
-        QSupportedWritingSystems supportedWritingSystems;
+        QBasicFontDatabase::addTTFile(QByteArray(), file);
-        QStringList families = addTTFile(QByteArray(), file, &supportedWritingSystems);
-
-        extern int qt_script_for_writing_system(QFontDatabase::WritingSystem writingSystem);
-        for (int i = 0; i < QFontDatabase::WritingSystemsCount; ++i) {
-            if (i == QFontDatabase::Any || supportedWritingSystems.supported(QFontDatabase::WritingSystem(i))) {
-                QChar::Script script = QChar::Script(qt_script_for_writing_system(QFontDatabase::WritingSystem(i)));
-                m_fallbacks[script] += families;
-            }
-        }
     }
 }
 
@@ -73,15 +64,16 @@ QStringList QAndroidPlatformFontDatabase::fallbacksForFamily(const QString &fami
                                                              QFont::StyleHint styleHint,
                                                              QChar::Script script) const
 {
-    Q_UNUSED(family);
+    QStringList result;
-    Q_UNUSED(style);
-
     if (styleHint == QFont::Monospace || styleHint == QFont::Courier)
-        return QString(qgetenv("QT_ANDROID_FONTS_MONOSPACE")).split(";") + m_fallbacks[script];
+        result.append(QString(qgetenv("QT_ANDROID_FONTS_MONOSPACE")).split(";"));
     else if (styleHint == QFont::Serif)
-        return QString(qgetenv("QT_ANDROID_FONTS_SERIF")).split(";") + m_fallbacks[script];
+        result.append(QString(qgetenv("QT_ANDROID_FONTS_SERIF")).split(";"));
+    else
+        result.append(QString(qgetenv("QT_ANDROID_FONTS")).split(";"));
+    result.append(QPlatformFontDatabase::fallbacksForFamily(family, style, styleHint, script));
 
-    return QString(qgetenv("QT_ANDROID_FONTS")).split(";") + m_fallbacks[script];
+    return result;
 }
 
 QT_END_NAMESPACE

src/plugins/platforms/android/qandroidplatformfontdatabase.h

@@ -47,9 +47,6 @@ public:
                                            QFont::Style style,
                                            QFont::StyleHint styleHint,
                                            QChar::Script script) const;
-
-private:
-    QHash<QChar::Script, QStringList> m_fallbacks;
 };
 
 QT_END_NAMESPACE

src/plugins/platforms/windows/qwindowsfontdatabase.cpp

@@ -1080,11 +1080,7 @@ QWindowsFontDatabase::~QWindowsFontDatabase()
 
 QFontEngineMulti *QWindowsFontDatabase::fontEngineMulti(QFontEngine *fontEngine, QChar::Script script)
 {
-    if (script == QChar::Script_Common)
     return new QWindowsMultiFontEngine(fontEngine, script);
-    // ### as long as fallbacksForFamily() does not take script parameter into account,
-    // prefer QFontEngineMulti's loadEngine() implementation for complex scripts
-    return QPlatformFontDatabase::fontEngineMulti(fontEngine, script);
 }
 
 QFontEngine * QWindowsFontDatabase::fontEngine(const QFontDef &fontDef, void *handle)
@@ -1666,11 +1662,10 @@ QString QWindowsFontDatabase::familyForStyleHint(QFont::StyleHint styleHint)
 
 QStringList QWindowsFontDatabase::fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const
 {
-    QStringList result = QPlatformFontDatabase::fallbacksForFamily(family, style, styleHint, script);
+    QStringList result;
-    if (!result.isEmpty())
-        return result;
     result.append(QWindowsFontDatabase::familyForStyleHint(styleHint));
     result.append(QWindowsFontDatabase::extraTryFontsForFamily(family));
+    result.append(QPlatformFontDatabase::fallbacksForFamily(family, style, styleHint, script));
 
     qCDebug(lcQpaFonts) << __FUNCTION__ << family << style << styleHint
         << script << result;

src/plugins/platforms/windows/qwindowsfontdatabase_ft.cpp

@@ -661,9 +661,7 @@ QFontEngine *QWindowsFontDatabaseFT::fontEngine(const QByteArray &fontData, qrea
 
 QStringList QWindowsFontDatabaseFT::fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const
 {
-    QStringList result = QPlatformFontDatabase::fallbacksForFamily(family, style, styleHint, script);
+    QStringList result;
-    if (!result.isEmpty())
-        return result;
 
     result.append(QWindowsFontDatabase::familyForStyleHint(styleHint));
 
@@ -679,6 +677,8 @@ QStringList QWindowsFontDatabaseFT::fallbacksForFamily(const QString &family, QF
 
     result.append(QWindowsFontDatabase::extraTryFontsForFamily(family));
 
+    result.append(QPlatformFontDatabase::fallbacksForFamily(family, style, styleHint, script));
+
     qCDebug(lcQpaFonts) << __FUNCTION__ << family << style << styleHint
         << script << result;