Make QWindowsMultiFontEngine support deferred fallback families query

This finishes 800232e1d3ebfbac28d07014a3c646ea00fcf6ad, which encovered
a tricky issue in QFontEngineMultiQPA::createMultiFontEngine().

Task-number: QTBUG-37836
Change-Id: I6d432e09e755f5d9ded09752c4c092f4857ad224
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

3 files changed, 9 insertions, 33 deletions

diff --git a/src/plugins/platforms/windows/qwindowsfontdatabase.cpp b/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
index 8f9ddc2168..1432dfdcd9 100644
--- a/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
+++ b/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
@@ -1040,8 +1040,7 @@ QWindowsFontDatabase::~QWindowsFontDatabase()
 
 QFontEngineMulti *QWindowsFontDatabase::fontEngineMulti(QFontEngine *fontEngine, QChar::Script script)
 {
-    Q_UNUSED(script)
-    return new QWindowsMultiFontEngine(fontEngine, QStringList());
+    return new QWindowsMultiFontEngine(fontEngine, script);
 }
 
 QFontEngine * QWindowsFontDatabase::fontEngine(const QFontDef &fontDef, void *handle)
diff --git a/src/plugins/platforms/windows/qwindowsfontengine.cpp b/src/plugins/platforms/windows/qwindowsfontengine.cpp
index c3774064e3..4f3a007bd7 100644
--- a/src/plugins/platforms/windows/qwindowsfontengine.cpp
+++ b/src/plugins/platforms/windows/qwindowsfontengine.cpp
@@ -1278,35 +1278,14 @@ void QWindowsFontEngine::initFontInfo(const QFontDef &request,
 
     Will probably be superseded by a common Free Type font engine in Qt 5.X.
 */
-
-QWindowsMultiFontEngine::QWindowsMultiFontEngine(QFontEngine *first, const QStringList &fallbacks)
-    : QFontEngineMulti(fallbacks.size() + 1),
-      fallbackFamilies(fallbacks)
-{
-    engines[0] = first;
-    first->ref.ref();
-    fontDef = engines[0]->fontDef;
-    cache_cost = first->cache_cost;
-}
-
-void QWindowsMultiFontEngine::setFallbackFamiliesList(const QStringList &fallbacks)
+QWindowsMultiFontEngine::QWindowsMultiFontEngine(QFontEngine *fe, int script)
+    : QFontEngineMultiQPA(fe, script)
 {
-    // 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)
 {
+    ensureFallbackFamiliesQueried();
     Q_ASSERT(at < engines.size());
     Q_ASSERT(engines.at(at) == 0);
 
@@ -1329,7 +1308,7 @@ void QWindowsMultiFontEngine::loadEngine(int at)
         data = fe->fontEngineData();
     }
 
-    const QString fam = fallbackFamilies.at(at-1);
+    const QString fam = fallbackFamilyAt(at - 1);
     memcpy(lf.lfFaceName, fam.utf16(), sizeof(wchar_t) * qMin(fam.length() + 1, 32));  // 32 = Windows hard-coded
 
 #ifndef QT_NO_DIRECTWRITE
diff --git a/src/plugins/platforms/windows/qwindowsfontengine.h b/src/plugins/platforms/windows/qwindowsfontengine.h
index 7d93484220..7a0803830c 100644
--- a/src/plugins/platforms/windows/qwindowsfontengine.h
+++ b/src/plugins/platforms/windows/qwindowsfontengine.h
@@ -53,7 +53,7 @@
 // We mean it.
 //
 
-#include <QtGui/private/qfontengine_p.h>
+#include <QtGui/private/qfontengine_qpa_p.h>
 
 #include <QtGui/QImage>
 #include <QtCore/QSharedPointer>
@@ -166,15 +166,13 @@ private:
     mutable int designAdvancesSize;
 };
 
-class QWindowsMultiFontEngine : public QFontEngineMulti
+
+class QWindowsMultiFontEngine : public QFontEngineMultiQPA
 {
 public:
-    QWindowsMultiFontEngine(QFontEngine *first, const QStringList &fallbacks);
+    explicit QWindowsMultiFontEngine(QFontEngine *fe, int script);
 
-    void setFallbackFamiliesList(const QStringList &fallbacks);
     void loadEngine(int at);
-
-    QStringList fallbackFamilies;
 };
 
 QT_END_NAMESPACE