Don't use the QGLSignalProxy to clean up the thread-local shaders.

After much back and forth I think we can use this approach for cleaning
up thread-local, shared resources. Main problem has been dealing with
dangling pointers and references, but they should be solved now.

3 files changed, 43 insertions, 17 deletions

diff --git a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
index 7d6d8a6..0ba324d 100644
--- a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
+++ b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
@@ -48,42 +48,59 @@
 
 QT_BEGIN_NAMESPACE
 
-class QGLThreadLocalShaders : public QObject
+
+// Handling the cleanup and creation of the thread-local shader cache
+// differes from other QGLContextResources. The cache needs to be
+// cleaned up when the thread exits, or when its group context is
+// destroyed.
+
+static void qt_gl_free_shared_shaders(void *value);
+
+class QGLThreadLocalShaders
 {
-    Q_OBJECT
 public:
     QGLThreadLocalShaders(const QGLContext *context, QGLEngineSharedShaders *shaders)
         : m_context(context), m_shaders(shaders)
     {
-        connect(QGLSignalProxy::instance(), SIGNAL(aboutToDestroyContext(const QGLContext*)),
-                SLOT(contextDestroyed(const QGLContext*)));
+        m_resource = new QGLContextResource(qt_gl_free_shared_shaders);
+        m_resource->insert(context, this);
     }
     ~QGLThreadLocalShaders() {
+        qDebug() << "Thread exit:";
         qDebug() << "~QGLThreadLocalShaders() for thread:" << hex << QThread::currentThread();
         qDebug() << "  -> deleting shader cache:" << hex << m_shaders;
         delete m_shaders;
+        // remove the resource from the group's resource list, so that
+        // the cleanup function is not called when the context is destroyed
+        m_resource->remove(m_context);
+        delete m_resource;
     }
     const QGLContext *m_context;
     QGLEngineSharedShaders *m_shaders;
-
-private slots:
-    void contextDestroyed(const QGLContext * context) {
-        if (context == m_context) {
-            qDebug() << "QGLThreadLocalShaders::contextDestroyed():";
-            qDebug() << "  -> cleaning up shader cache for thread:" << hex << QThread::currentThread();
-            qDebug() << "  -> shaders:" << hex << m_shaders;
-            m_shaders->cleanupBeforeDestruction();
-        }
-    }
+    QGLContextResource *m_resource;
 };
 
+static void qt_gl_free_shared_shaders(void *value)
+{
+    QGLThreadLocalShaders *local = reinterpret_cast<QGLThreadLocalShaders *>(value);
+    qDebug() << "Context destroyed:";
+    qDebug() << " -> deleting shader cache" << hex << local->m_shaders;
+    delete local->m_shaders;
+    local->m_shaders = 0;
+
+    // this function is called when the context group for the context
+    // we have ref'ed is deleted - that means our context ptr is no
+    // longer valid
+    local->m_context = 0;
+}
+
 class QGLShaderStorage
 {
 public:
     QGLEngineSharedShaders *shadersForThread(const QGLContext *context) {
         QGLThreadLocalShaders *shaders = m_storage.localData();
         if (!shaders) {
-            qDebug() << "new shader cache for thread:" << hex << QThread::currentThread();
+            qDebug() << "New shader cache for thread:" << hex << QThread::currentThread();
             QGLShareContextScope scope(context);
             shaders = new QGLThreadLocalShaders(context, new QGLEngineSharedShaders(context));
             qDebug() << "  -> context:" << context;
@@ -840,5 +857,3 @@ bool QGLEngineShaderManager::useCorrectShaderProg()
 }
 
 QT_END_NAMESPACE
-
-#include "qglengineshadermanager.moc"
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 995e753..1223552 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -5377,6 +5377,15 @@ void QGLContextResource::cleanup(const QGLContext *ctx, void *value)
     active.deref();
 }
 
+void QGLContextResource::remove(const QGLContext *ctx)
+{
+    if (ctx) {
+        QGLContextGroup *group = QGLContextPrivate::contextGroup(ctx);
+        group->m_resources.remove(this);
+        active.deref();
+    }
+}
+
 void QGLContextGroup::cleanupResources(const QGLContext *ctx)
 {
     // If there are still shares, then no cleanup to be done yet.
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 9b862eb..d5083e9 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -624,6 +624,8 @@ public:
     void *value(const QGLContext *key);
     // Cleanup 'value' in response to a context group being destroyed.
     void cleanup(const QGLContext *ctx, void *value);
+    // Remove this resource from the group's resource list.
+    void remove(const QGLContext *ctx);
 private:
     FreeFunc free;
     QAtomicInt active;