Prevent crash in QGLGlyphCache due to dangling context references.

We need to clear the context from the cache when it's destroyed even if
it doesn't belong to a widget.

Task-number: QTBUG-13622
Reviewed-by: Trond
(cherry picked from commit cb764eaf91e3a8ef30b280671d5c991ec926d14c)

1 files changed, 5 insertions, 3 deletions

diff --git a/src/opengl/qpaintengine_opengl.cpp b/src/opengl/qpaintengine_opengl.cpp
index 15fb932f4d..e954e1d88f 100644
--- a/src/opengl/qpaintengine_opengl.cpp
+++ b/src/opengl/qpaintengine_opengl.cpp
@@ -4737,9 +4737,11 @@ void QGLGlyphCache::cacheGlyphs(QGLContext *context, const QTextItemInt &ti,
         font_cache = new QGLFontGlyphHash;
 //         qDebug() << "new context" << context << font_cache;
         qt_context_cache.insert(context, font_cache);
-        if (context->isValid() && context->device()->devType() == QInternal::Widget) {
-            QWidget *widget = static_cast<QWidget *>(context->device());
-            connect(widget, SIGNAL(destroyed(QObject*)), SLOT(widgetDestroyed(QObject*)));
+        if (context->isValid()) {
+            if (context->device()->devType() == QInternal::Widget) {
+                QWidget *widget = static_cast<QWidget *>(context->device());
+                connect(widget, SIGNAL(destroyed(QObject*)), SLOT(widgetDestroyed(QObject*)));
+            }
             connect(QGLSignalProxy::instance(),
                     SIGNAL(aboutToDestroyContext(const QGLContext*)),
                     SLOT(cleanupContext(const QGLContext*)));