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/hardwarebuffer.cpp

@@ -0,0 +1,43 @@
+/*
+ * 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.
+ */
+
+#include "hardwarebuffer.h"
+#include "graphics.h"
+
+#include <framework/application.h>
+#include <framework/core/logger.h>
+
+HardwareBuffer::HardwareBuffer(Type type)
+{
+    m_type = type;
+    m_id = 0;
+    glGenBuffers(1, &m_id);
+    if(!m_id)
+        g_logger.fatal("Unable to create hardware buffer.");
+}
+
+HardwareBuffer::~HardwareBuffer()
+{
+    assert(!g_app->isTermianted());
+    if(g_graphics.ok())
+        glDeleteBuffers(1, &m_id);
+}