Guarantee QPFDB::fontEngine() always return non-multi font engine

After QPA refactoring, QWindowsFontDatabase::fontEngine() was returning
a multi font engine w/o any particular reason.
This makes the code more obvious and opens the road to further improvements.

Change-Id: I4858026ddf774d3159c89357b1c905f5112b1c51
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/gui/text/qfontdatabase.cpp

@@ -790,6 +790,7 @@ QFontEngine *loadSingleEngine(int script,
     if (!engine) {
         engine = pfdb->fontEngine(def, size->handle);
         if (engine) {
+            Q_ASSERT(engine->type() != QFontEngine::Multi);
             // Also check for OpenType tables when using complex scripts
             if (!engine->supportsScript(QChar::Script(script))) {
                 qWarning("  OpenType support missing for script %d", script);
@@ -809,12 +810,10 @@ QFontEngine *loadEngine(int script, const QFontDef &request,
                         QtFontFamily *family, QtFontFoundry *foundry,
                         QtFontStyle *style, QtFontSize *size)
 {
-
     QFontEngine *engine = loadSingleEngine(script, request, foundry, style, size);
+    Q_ASSERT(!engine || engine->type() != QFontEngine::Multi);
+    if (engine && !(request.styleStrategy & QFont::NoFontMerging) && !engine->symbol) {
         // make sure that the db has all fallback families
-    if (engine && engine->type() != QFontEngine::Multi
-        && !(request.styleStrategy & QFont::NoFontMerging) && !engine->symbol ) {
-
         if (family && !family->askedForFallback) {
             QFont::Style fontStyle = QFont::Style(style->key.style);
             QFont::StyleHint styleHint = QFont::StyleHint(request.styleHint);

src/plugins/platforms/windows/qwindowsfontdatabase.cpp

@@ -1038,11 +1038,17 @@ QWindowsFontDatabase::~QWindowsFontDatabase()
     removeApplicationFonts();
 }
 
+QFontEngineMulti *QWindowsFontDatabase::fontEngineMulti(QFontEngine *fontEngine, QChar::Script script)
+{
+    Q_UNUSED(script)
+    return new QWindowsMultiFontEngine(fontEngine, QStringList());
+}
+
 QFontEngine * QWindowsFontDatabase::fontEngine(const QFontDef &fontDef, void *handle)
 {
-    QFontEngine *fe = QWindowsFontDatabase::createEngine(QChar::Script_Common, fontDef,
+    QFontEngine *fe = QWindowsFontDatabase::createEngine(fontDef, 0,
-                                              0, QWindowsContext::instance()->defaultDPI(), false,
+                                                         QWindowsContext::instance()->defaultDPI(),
-                                              QStringList(), sharedFontData());
+                                                         false, sharedFontData());
     qCDebug(lcQpaFonts) << __FUNCTION__ << "FONTDEF" << fontDef << fe << handle;
     return fe;
 }
@@ -1087,12 +1093,12 @@ QFontEngine *QWindowsFontDatabase::fontEngine(const QByteArray &fontData, qreal
             QFontDef request;
             request.family = uniqueFamilyName;
             request.pixelSize = pixelSize;
-            request.styleStrategy = QFont::NoFontMerging | QFont::PreferMatch;
+            request.styleStrategy = QFont::PreferMatch;
             request.hintingPreference = hintingPreference;
 
-            fontEngine = QWindowsFontDatabase::createEngine(QChar::Script_Common, request, 0,
+            fontEngine = QWindowsFontDatabase::createEngine(request, 0,
-                    QWindowsContext::instance()->defaultDPI(), false, QStringList(),
+                                                            QWindowsContext::instance()->defaultDPI(),
-                    sharedFontData());
+                                                            false, sharedFontData());
 
             if (fontEngine) {
                 if (request.family != fontEngine->fontDef.family) {
@@ -1623,9 +1629,8 @@ QStringList QWindowsFontDatabase::fallbacksForFamily(const QString &family, QFon
 }
 
 
-QFontEngine *QWindowsFontDatabase::createEngine(int script, const QFontDef &request,
+QFontEngine *QWindowsFontDatabase::createEngine(const QFontDef &request,
                                                 HDC fontHdc, int dpi, bool rawMode,
-                                                const QStringList &family_list,
                                                 const QSharedPointer<QWindowsFontEngineData> &data)
 {
     LOGFONT lf;
@@ -1769,17 +1774,6 @@ QFontEngine *QWindowsFontDatabase::createEngine(int script, const QFontDef &requ
         directWriteFont->Release();
 #endif
 
-    if ((script == QChar::Script_Common || script == QChar::Script_Han)
-            && !(request.styleStrategy & QFont::NoFontMerging)) {
-        const QStringList extraFonts = QWindowsFontDatabase::extraTryFontsForFamily(request.family);
-        if (extraFonts.size()) {
-            QStringList list = family_list;
-            list.append(extraFonts);
-            QFontEngine *mfe = new QWindowsMultiFontEngine(fe, list);
-            mfe->fontDef = fe->fontDef;
-            fe = mfe;
-        }
-    }
     return fe;
 }
 

src/plugins/platforms/windows/qwindowsfontdatabase.h

@@ -78,6 +78,7 @@ public:
     ~QWindowsFontDatabase();
 
     virtual void populateFontDatabase();
+    virtual QFontEngineMulti *fontEngineMulti(QFontEngine *fontEngine, QChar::Script script);
     virtual QFontEngine *fontEngine(const QFontDef &fontDef, void *handle);
     virtual QFontEngine *fontEngine(const QByteArray &fontData, qreal pixelSize, QFont::HintingPreference hintingPreference);
     virtual QStringList fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const;
@@ -92,9 +93,8 @@ public:
 
     static QFont systemDefaultFont();
 
-    static QFontEngine *createEngine(int script, const QFontDef &request,
+    static QFontEngine *createEngine(const QFontDef &request,
                                      HDC fontHdc, int dpi, bool rawMode,
-                                     const QStringList &family_list,
                                      const QSharedPointer<QWindowsFontEngineData> &data);
 
     static HFONT systemFont();

src/plugins/platforms/windows/qwindowsfontengine.cpp

@@ -1233,15 +1233,11 @@ QFontEngine *QWindowsFontEngine::cloneWithSize(qreal pixelSize) const
     if (!uniqueFamilyName.isEmpty())
         request.family = uniqueFamilyName;
     request.pixelSize = pixelSize;
-    // Disable font merging, as otherwise createEngine will return a multi-engine
-    // instance instead of the specific engine we wish to clone.
-    request.styleStrategy |= QFont::NoFontMerging;
 
     QFontEngine *fontEngine =
-        QWindowsFontDatabase::createEngine(QChar::Script_Common, request, 0,
+        QWindowsFontDatabase::createEngine(request, 0,
                                            QWindowsContext::instance()->defaultDPI(),
-                                           false,
+                                           false, m_fontEngineData);
-                                           QStringList(), m_fontEngineData);
     if (fontEngine) {
         fontEngine->fontDef.family = actualFontName;
         if (!uniqueFamilyName.isEmpty()) {
@@ -1285,18 +1281,28 @@ void QWindowsFontEngine::initFontInfo(const QFontDef &request,
 
 QWindowsMultiFontEngine::QWindowsMultiFontEngine(QFontEngine *first, const QStringList &fallbacks)
     : QFontEngineMulti(fallbacks.size() + 1),
-          fallbacks(fallbacks)
+      fallbackFamilies(fallbacks)
 {
-    qCDebug(lcQpaFonts) << __FUNCTION__ << engines.size() << first << first->fontDef.family << fallbacks;
     engines[0] = first;
     first->ref.ref();
     fontDef = engines[0]->fontDef;
     cache_cost = first->cache_cost;
 }
 
-QWindowsMultiFontEngine::~QWindowsMultiFontEngine()
+void QWindowsMultiFontEngine::setFallbackFamiliesList(const QStringList &fallbacks)
 {
-    qCDebug(lcQpaFonts) << __FUNCTION__;
+    // Original FontEngine to restore after the fill.
+    QFontEngine *fe = engines[0];
+    fallbackFamilies = fallbacks;
+    if (!fallbackFamilies.isEmpty()) {
+        engines.fill(0, fallbackFamilies.size() + 1);
+        engines[0] = fe;
+    } else {
+        // Turns out we lied about having any fallback at all.
+        fallbackFamilies << fe->fontDef.family;
+        engines[1] = fe;
+        fe->ref.ref();
+    }
 }
 
 void QWindowsMultiFontEngine::loadEngine(int at)
@@ -1323,7 +1329,7 @@ void QWindowsMultiFontEngine::loadEngine(int at)
         data = fe->fontEngineData();
     }
 
-    const QString fam = fallbacks.at(at-1);
+    const QString fam = fallbackFamilies.at(at-1);
     memcpy(lf.lfFaceName, fam.utf16(), sizeof(wchar_t) * qMin(fam.length() + 1, 32));  // 32 = Windows hard-coded
 
 #ifndef QT_NO_DIRECTWRITE

src/plugins/platforms/windows/qwindowsfontengine.h

@@ -170,10 +170,11 @@ class QWindowsMultiFontEngine : public QFontEngineMulti
 {
 public:
     QWindowsMultiFontEngine(QFontEngine *first, const QStringList &fallbacks);
-    virtual ~QWindowsMultiFontEngine();
+
+    void setFallbackFamiliesList(const QStringList &fallbacks);
     void loadEngine(int at);
 
-    QStringList fallbacks;
+    QStringList fallbackFamilies;
 };
 
 QT_END_NAMESPACE