fixed various caching issues

app/render/renderframebuffer.h

@@ -27,6 +27,7 @@
 
 class RenderFramebuffer : public QObject
 {
+  Q_OBJECT
 public:
   RenderFramebuffer();
   ~RenderFramebuffer();
@@ -37,8 +38,6 @@ public:
 
   void Create(QOpenGLContext *ctx);
 
-  void Destroy();
-
   bool IsCreated() const;
 
   void Bind();
@@ -53,6 +52,9 @@ public:
 
   const GLuint& buffer() const;
 
+public slots:
+  void Destroy();
+
 private:
   void AttachInternal(GLuint tex);