fixed various caching issues

app/render/rendertexture.h

@@ -26,13 +26,9 @@
 
 #include "pixelformat.h"
 
-// FIXME: Test code
-#include <QMutex>
-extern QMutex m;
-// End test code
-
 class RenderTexture : public QObject
 {
+  Q_OBJECT
 public:
   enum Type {
     kSingleBuffer,
@@ -51,8 +47,6 @@ public:
 
   bool IsCreated() const;
 
-  void Destroy();
-
   void Bind();
 
   void Release();
@@ -73,6 +67,9 @@ public:
 
   uchar *Download() const;
 
+public slots:
+  void Destroy();
+
 private:
   void CreateInternal(GLuint *tex, void *data = nullptr);