QFontCache: Centralize the engine type safety check

We depend on the assumption QFontCache::findEngine(key) for key.multi=1
returns a font engine of type QFontEngine::Multi;
guarantee that by checking it in a single place.

Change-Id: I287da4fd62deb22fc5520cde5b0505bc44547609
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

3 files changed, 9 insertions, 4 deletions

diff --git a/src/gui/text/qfont.cpp b/src/gui/text/qfont.cpp
index bc9da5b564..2c5a0c74fc 100644
--- a/src/gui/text/qfont.cpp
+++ b/src/gui/text/qfont.cpp
@@ -2809,6 +2809,10 @@ QFontEngine *QFontCache::findEngine(const Key &key)
     EngineCache::Iterator it = engineCache.find(key),
                          end = engineCache.end();
     if (it == end) return 0;
+
+    Q_ASSERT(it.value().data != Q_NULLPTR);
+    Q_ASSERT(key.multi == (it.value().data->type() == QFontEngine::Multi));
+
     // found... update the hitcount and timestamp
     updateHitCountAndTimeStamp(it.value());
 
@@ -2829,6 +2833,9 @@ void QFontCache::updateHitCountAndTimeStamp(Engine &value)
 
 void QFontCache::insertEngine(const Key &key, QFontEngine *engine, bool insertMulti)
 {
+    Q_ASSERT(engine != Q_NULLPTR);
+    Q_ASSERT(key.multi == (engine->type() == QFontEngine::Multi));
+
 #ifdef QFONTCACHE_DEBUG
     FC_DEBUG("QFontCache: inserting new engine %p, refcount %d", engine, engine->ref.load());
     if (!insertMulti && engineCache.contains(key)) {
diff --git a/src/gui/text/qfontdatabase.cpp b/src/gui/text/qfontdatabase.cpp
index c41b3d2c18..333f1d2bb0 100644
--- a/src/gui/text/qfontdatabase.cpp
+++ b/src/gui/text/qfontdatabase.cpp
@@ -935,7 +935,6 @@ QFontEngine *loadSingleEngine(int script,
             engine = fontCache->findEngine(key);
             key.script = script;
             if (engine) {
-                Q_ASSERT(engine->type() != QFontEngine::Multi);
                 // Also check for OpenType tables when using complex scripts
                 if (Q_UNLIKELY(!engine->supportsScript(QChar::Script(script)))) {
                     qWarning("  OpenType support missing for script %d", script);
@@ -958,7 +957,6 @@ QFontEngine *loadSingleEngine(int script,
 
         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);
@@ -986,7 +984,7 @@ QFontEngine *loadEngine(int script, const QFontDef &request,
                         QtFontStyle *style, QtFontSize *size)
 {
     QFontEngine *engine = loadSingleEngine(script, request, family, foundry, style, size);
-    Q_ASSERT(!engine || engine->type() != QFontEngine::Multi);
+
     if (engine && !(request.styleStrategy & QFont::NoFontMerging) && !engine->symbol) {
         QPlatformFontDatabase *pfdb = QGuiApplicationPrivate::platformIntegration()->fontDatabase();
         QFontEngineMulti *pfMultiEngine = pfdb->fontEngineMulti(engine, QChar::Script(script));
diff --git a/tests/auto/gui/text/qfontcache/tst_qfontcache.cpp b/tests/auto/gui/text/qfontcache/tst_qfontcache.cpp
index 272827e57b..c92b7eed58 100644
--- a/tests/auto/gui/text/qfontcache/tst_qfontcache.cpp
+++ b/tests/auto/gui/text/qfontcache/tst_qfontcache.cpp
@@ -110,7 +110,7 @@ void tst_QFontCache::clear()
         fontEngine->ref.ref();
 
         // cache the engine once again; there is a special case when the engine is cached more than once
-        QFontCache::instance()->insertEngine(QFontCache::Key(QFontDef(), 0, 0), fontEngine);
+        QFontCache::instance()->insertEngine(QFontCache::Key(QFontDef(), 0, 1), fontEngine);
     }
 
     // use it: