Fix memory leaks

* Fix recursive reference memory leak in UIWidget
* Make Event/ScheduledEvent memory-leak safe
* Fix exit crashs by freeing graphics resources before destroying GL context
* Add many asserts to avoid any leak regression

src/framework/graphics/framebuffermanager.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2010-2012 OTClient <https://github.com/edubart/otclient>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+
+#ifndef FRAMEBUFFERMANAGER_H
+#define FRAMEBUFFERMANAGER_H
+
+#include "framebuffer.h"
+
+class FrameBufferManager
+{
+public:
+    void init();
+    void terminate();
+    void clear();
+
+    FrameBufferPtr createFrameBuffer();
+    const FrameBufferPtr& getTemporaryFrameBuffer() { return m_temporaryFramebuffer; }
+
+protected:
+    FrameBufferPtr m_temporaryFramebuffer;
+    std::vector<FrameBufferPtr> m_framebuffers;
+};
+
+extern FrameBufferManager g_framebuffers;
+
+#endif