Use the lazily-queried families for all QPA multi font engines.

This is the approach introduced together with the  WebKit "backdoor"
that lets us use QRawFont with QTextLayout. We could use it all
over the place and share more code.

Change-Id: Ie1963679755f37ba9204d67554a163f1d1115604
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>

11 files changed, 53 insertions, 40 deletions

diff --git a/src/gui/text/qfontdatabase_qpa.cpp b/src/gui/text/qfontdatabase_qpa.cpp
index 1a1f08f73d..0014efc450 100644
--- a/src/gui/text/qfontdatabase_qpa.cpp
+++ b/src/gui/text/qfontdatabase_qpa.cpp
@@ -207,7 +207,9 @@ QFontEngine *loadEngine(int script, const QFontDef &request,
             fallbacks = family->fallbackFamilies;
 
         QPlatformFontDatabase *pfdb = QGuiApplicationPrivate::platformIntegration()->fontDatabase();
-        engine = pfdb->fontEngineMulti(engine, QUnicodeTables::Script(script), fallbacks);
+        QFontEngineMulti *pfMultiEngine = pfdb->fontEngineMulti(engine, QUnicodeTables::Script(script));
+        pfMultiEngine->setFallbackFamiliesList(fallbacks);
+        engine = pfMultiEngine;
 
         // Cache Multi font engine as well in case we got the FT single
         // font engine when we are actually looking for a Multi one
diff --git a/src/gui/text/qfontengine.cpp b/src/gui/text/qfontengine.cpp
index 364a356b96..5c18ddeef8 100644
--- a/src/gui/text/qfontengine.cpp
+++ b/src/gui/text/qfontengine.cpp
@@ -1366,6 +1366,7 @@ bool QFontEngineMulti::stringToCMap(const QChar *str, int len,
     if (!engine(0)->stringToCMap(str, len, glyphs, &ng, flags))
         return false;
 
+    const_cast<QFontEngineMulti *>(this)->ensureFallbackFamiliesQueried();
     int glyph_pos = 0;
     for (int i = 0; i < len; ++i) {
         bool surrogate = (str[i].isHighSurrogate() && i < len-1 && str[i+1].isLowSurrogate());
diff --git a/src/gui/text/qfontengine_p.h b/src/gui/text/qfontengine_p.h
index 1114cdf12c..4741de3000 100644
--- a/src/gui/text/qfontengine_p.h
+++ b/src/gui/text/qfontengine_p.h
@@ -395,12 +395,14 @@ public:
     }
 
     virtual bool shouldLoadFontEngineForCharacter(int at, uint ucs4) const;
+    virtual void setFallbackFamiliesList(const QStringList &) {}
 
 protected:
     friend class QPSPrintEnginePrivate;
     friend class QPSPrintEngineFontMulti;
     friend class QRawFont;
     virtual void loadEngine(int at) = 0;
+    virtual void ensureFallbackFamiliesQueried() {}
     QVector<QFontEngine *> engines;
 };
 
diff --git a/src/gui/text/qfontengine_qpa.cpp b/src/gui/text/qfontengine_qpa.cpp
index 48679824a4..d12e2d651c 100644
--- a/src/gui/text/qfontengine_qpa.cpp
+++ b/src/gui/text/qfontengine_qpa.cpp
@@ -674,6 +674,7 @@ QFontEngineMultiQPA::QFontEngineMultiQPA(QFontEngine *fe, int _script)
     , script(_script)
     , fallbacksQueried(false)
 {
+    fallbackFamilies << QString();
     init(fe);
 }
 
@@ -688,36 +689,43 @@ void QFontEngineMultiQPA::init(QFontEngine *fe)
 
 void QFontEngineMultiQPA::loadEngine(int at)
 {
-    bool canLoadFallbackEngine = true;
-    if (!fallbacksQueried) {
-        // Original FontEngine to restore after the fill.
-        QFontEngine *fe = engines[0];
-        fallbackFamilies = QGuiApplicationPrivate::instance()->platformIntegration()->fontDatabase()->fallbacksForFamily(fe->fontDef.family, QFont::Style(fe->fontDef.style)
-                                                                                                                         , QFont::AnyStyle, QUnicodeTables::Script(script));
-        if (fallbackFamilies.size() > 1) {
-            engines.fill(0, fallbackFamilies.size() + 1);
-            engines[0] = fe;
-        } else {
-            // Turns out we lied about having any fallback at all.
-            canLoadFallbackEngine = false;
-            engines[1] = fe;
-        }
-        fallbacksQueried = true;
-    }
+    ensureFallbackFamiliesQueried();
     Q_ASSERT(at < engines.size());
     Q_ASSERT(engines.at(at) == 0);
     QFontDef request = fontDef;
-    if (canLoadFallbackEngine) {
-        request.styleStrategy |= QFont::NoFontMerging;
-        request.family = fallbackFamilies.at(at-1);
-        engines[at] = QFontDatabase::findFont(script,
-                                              /*fontprivate = */0,
-                                              request, /*multi = */false);
-    }
+    request.styleStrategy |= QFont::NoFontMerging;
+    request.family = fallbackFamilies.at(at-1);
+    engines[at] = QFontDatabase::findFont(script,
+                                          /*fontprivate = */0,
+                                          request, /*multi = */false);
     Q_ASSERT(engines[at]);
     engines[at]->ref.ref();
     engines[at]->fontDef = request;
 }
+void QFontEngineMultiQPA::ensureFallbackFamiliesQueried()
+{
+    if (fallbacksQueried)
+        return;
+    QStringList fallbacks = QGuiApplicationPrivate::instance()->platformIntegration()->fontDatabase()->fallbacksForFamily(engine(0)->fontDef.family, QFont::Style(engine(0)->fontDef.style)
+                                                                                                                     , QFont::AnyStyle, QUnicodeTables::Script(script));
+    setFallbackFamiliesList(fallbacks);
+}
+
+void QFontEngineMultiQPA::setFallbackFamiliesList(const QStringList &fallbacks)
+{
+    // 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;
+    }
+    fallbacksQueried = true;
+}
 
 /*
   This is used indirectly by QtWebKit when using QTextLayout::setRawFont
@@ -750,7 +758,7 @@ QFontEngine* QFontEngineMultiQPA::createMultiFontEngine(QFontEngine *fe, int scr
         it++;
     }
     if (!engine) {
-        engine = new QFontEngineMultiQPA(fe, script);
+        engine = QGuiApplicationPrivate::instance()->platformIntegration()->fontDatabase()->fontEngineMulti(fe, QUnicodeTables::Script(script));
         QFontCache::instance()->insertEngine(key, engine, /* insertMulti */ !faceIsLocal);
     }
     Q_ASSERT(engine);
diff --git a/src/gui/text/qfontengine_qpa_p.h b/src/gui/text/qfontengine_qpa_p.h
index 16991ad2ca..e6907149b2 100644
--- a/src/gui/text/qfontengine_qpa_p.h
+++ b/src/gui/text/qfontengine_qpa_p.h
@@ -247,6 +247,7 @@ class Q_GUI_EXPORT QFontEngineMultiQPA : public QFontEngineMulti
 {
 public:
     QFontEngineMultiQPA(QFontEngine *fe, int script, const QStringList &fallbacks);
+    QFontEngineMultiQPA(QFontEngine *fe, int script);
 
     void loadEngine(int at);
     static QFontEngine* createMultiFontEngine(QFontEngine *fe, int script);
@@ -254,13 +255,15 @@ public:
     int fallbackFamilyCount() const { return fallbackFamilies.size(); }
     QString fallbackFamilyAt(int at) const { return fallbackFamilies.at(at); }
 
+    virtual void ensureFallbackFamiliesQueried();
+    virtual void setFallbackFamiliesList(const QStringList &fallbacks);
+
 private:
-    QFontEngineMultiQPA(QFontEngine *fe, int script);
     void init(QFontEngine *fe);
 
-    QStringList fallbackFamilies;
+    mutable QStringList fallbackFamilies;
     int script;
-    bool fallbacksQueried;
+    mutable bool fallbacksQueried;
 };
 
 QT_END_NAMESPACE
diff --git a/src/gui/text/qplatformfontdatabase_qpa.cpp b/src/gui/text/qplatformfontdatabase_qpa.cpp
index 47a9fe5ab1..6bd8284fa0 100644
--- a/src/gui/text/qplatformfontdatabase_qpa.cpp
+++ b/src/gui/text/qplatformfontdatabase_qpa.cpp
@@ -276,10 +276,9 @@ void QPlatformFontDatabase::populateFontDatabase()
     a certain character.
 */
 QFontEngineMulti *QPlatformFontDatabase::fontEngineMulti(QFontEngine *fontEngine,
-                                                         QUnicodeTables::Script script,
-                                                         const QStringList &fallbacks)
+                                                         QUnicodeTables::Script script)
 {
-    return new QFontEngineMultiQPA(fontEngine, script, fallbacks);
+    return new QFontEngineMultiQPA(fontEngine, script);
 }
 
 /*!
diff --git a/src/gui/text/qplatformfontdatabase_qpa.h b/src/gui/text/qplatformfontdatabase_qpa.h
index 5a5a8f321f..3810b75dbf 100644
--- a/src/gui/text/qplatformfontdatabase_qpa.h
+++ b/src/gui/text/qplatformfontdatabase_qpa.h
@@ -89,7 +89,7 @@ class Q_GUI_EXPORT QPlatformFontDatabase
 public:
     virtual ~QPlatformFontDatabase();
     virtual void populateFontDatabase();
-    virtual QFontEngineMulti *fontEngineMulti(QFontEngine *fontEngine, QUnicodeTables::Script script, const QStringList &fallbacks);
+    virtual QFontEngineMulti *fontEngineMulti(QFontEngine *fontEngine, QUnicodeTables::Script script);
     virtual QFontEngine *fontEngine(const QFontDef &fontDef, QUnicodeTables::Script script, void *handle);
     virtual QStringList fallbacksForFamily(const QString family, const QFont::Style &style, const QFont::StyleHint &styleHint, const QUnicodeTables::Script &script) const;
     virtual QStringList addApplicationFont(const QByteArray &fontData, const QString &fileName);
diff --git a/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp b/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp
index 28a99cfd17..a4d2778ba6 100644
--- a/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp
+++ b/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp
@@ -472,10 +472,9 @@ void QFontconfigDatabase::populateFontDatabase()
 }
 
 QFontEngineMulti *QFontconfigDatabase::fontEngineMulti(QFontEngine *fontEngine,
-                                                       QUnicodeTables::Script script,
-                                                       const QStringList &fallbacks)
+                                                       QUnicodeTables::Script script)
 {
-    return new QFontEngineMultiFontConfig(fontEngine, script, fallbacks);
+    return new QFontEngineMultiFontConfig(fontEngine, script);
 }
 
 QFontEngine *QFontconfigDatabase::fontEngine(const QFontDef &f, QUnicodeTables::Script script, void *usrPtr)
diff --git a/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase_p.h b/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase_p.h
index d4742167e9..df62ddeb0b 100644
--- a/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase_p.h
+++ b/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase_p.h
@@ -51,7 +51,7 @@ class QFontconfigDatabase : public QBasicFontDatabase
 {
 public:
     void populateFontDatabase();
-    QFontEngineMulti *fontEngineMulti(QFontEngine *fontEngine, QUnicodeTables::Script script, const QStringList &fallbacks);
+    QFontEngineMulti *fontEngineMulti(QFontEngine *fontEngine, QUnicodeTables::Script script);
     QFontEngine *fontEngine(const QFontDef &fontDef, QUnicodeTables::Script script, void *handle);
     QStringList fallbacksForFamily(const QString family, const QFont::Style &style, const QFont::StyleHint &styleHint, const QUnicodeTables::Script &script) const;
     QStringList addApplicationFont(const QByteArray &fontData, const QString &fileName);
diff --git a/src/platformsupport/fontdatabases/fontconfig/qfontenginemultifontconfig.cpp b/src/platformsupport/fontdatabases/fontconfig/qfontenginemultifontconfig.cpp
index 2016500767..31828ef01f 100644
--- a/src/platformsupport/fontdatabases/fontconfig/qfontenginemultifontconfig.cpp
+++ b/src/platformsupport/fontdatabases/fontconfig/qfontenginemultifontconfig.cpp
@@ -46,9 +46,8 @@
 
 QT_BEGIN_NAMESPACE
 
-QFontEngineMultiFontConfig::QFontEngineMultiFontConfig(QFontEngine *fe, int script,
-                                                       const QStringList &fallbacks)
-    : QFontEngineMultiQPA(fe, script, fallbacks)
+QFontEngineMultiFontConfig::QFontEngineMultiFontConfig(QFontEngine *fe, int script)
+    : QFontEngineMultiQPA(fe, script)
 {
 }
 
diff --git a/src/platformsupport/fontdatabases/fontconfig/qfontenginemultifontconfig_p.h b/src/platformsupport/fontdatabases/fontconfig/qfontenginemultifontconfig_p.h
index 260a9b5c70..046d63c190 100644
--- a/src/platformsupport/fontdatabases/fontconfig/qfontenginemultifontconfig_p.h
+++ b/src/platformsupport/fontdatabases/fontconfig/qfontenginemultifontconfig_p.h
@@ -51,7 +51,7 @@ class QFontEngineMultiFontConfig : public QFontEngineMultiQPA
 {
     Q_OBJECT
 public:
-    explicit QFontEngineMultiFontConfig(QFontEngine *fe, int script, const QStringList &fallbacks);
+    explicit QFontEngineMultiFontConfig(QFontEngine *fe, int script);
 
     ~QFontEngineMultiFontConfig();