Fix possible crash in glyph cache when deleting and creating contexts

The freeResource(), used in the glyph cache as a notifier of when the
owner context of the cache disappears, is never called if the context
is in a group with other contexts that share its resources. This
implements a second notifier function instead which can be used to
invalidate the glyph cache when its context is destroyed.

Task-number: QTBUG-22324
Reviewed-by: Samuel

3 files changed, 15 insertions, 1 deletions

diff --git a/src/opengl/gl2paintengineex/qtextureglyphcache_gl_p.h b/src/opengl/gl2paintengineex/qtextureglyphcache_gl_p.h
index 83ca06d040..1a8bb0bb71 100644
--- a/src/opengl/gl2paintengineex/qtextureglyphcache_gl_p.h
+++ b/src/opengl/gl2paintengineex/qtextureglyphcache_gl_p.h
@@ -144,6 +144,10 @@ public:
 
     void clear();
 
+    void contextDeleted(const QGLContext *context) {
+        if (ctx == context)
+            ctx = 0;
+    }
     void freeResource(void *) { ctx = 0; }
 
 private:
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 423fa08a1f..eaaf9a8569 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -5722,6 +5722,11 @@ void QGLContextGroupResourceBase::cleanup(const QGLContext *ctx)
     }
 }
 
+void QGLContextGroupResourceBase::contextDeleted(const QGLContext *ctx)
+{
+    Q_UNUSED(ctx);
+}
+
 void QGLContextGroupResourceBase::cleanup(const QGLContext *ctx, void *value)
 {
 #ifdef QT_GL_CONTEXT_RESOURCE_DEBUG
@@ -5737,12 +5742,16 @@ void QGLContextGroupResourceBase::cleanup(const QGLContext *ctx, void *value)
 
 void QGLContextGroup::cleanupResources(const QGLContext *context)
 {
+    // Notify all resources that a context has been deleted
+    QHash<QGLContextGroupResourceBase *, void *>::ConstIterator it;
+    for (it = m_resources.begin(); it != m_resources.end(); ++it)
+        it.key()->contextDeleted(context);
+
     // If there are still shares, then no cleanup to be done yet.
     if (m_shares.size() > 1)
         return;
 
     // Iterate over all resources and free each in turn.
-    QHash<QGLContextGroupResourceBase *, void *>::ConstIterator it;
     for (it = m_resources.begin(); it != m_resources.end(); ++it)
         it.key()->cleanup(context, it.value());
 }
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index de349a759d..b6fc96a55c 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -725,6 +725,7 @@ public:
     void cleanup(const QGLContext *context);
     void cleanup(const QGLContext *context, void *value);
     virtual void freeResource(void *value) = 0;
+    virtual void contextDeleted(const QGLContext *ctx);
 
 protected:
     QList<QGLContextGroup *> m_groups;