some render cache adjustments

app/node/processor/renderer/rendererthreadbase.h

@@ -46,13 +46,11 @@ public:
   virtual void run() override;
 
 public slots:
-  void Cancel();
+  virtual void Cancel() = 0;
 
 protected:
   virtual void ProcessLoop() = 0;
 
-  bool Cancelled();
-
   QWaitCondition wait_cond_;
 
   QMutex mutex_;
@@ -62,8 +60,6 @@ protected:
 private:
   QOpenGLContext* share_ctx_;
 
-  bool cancelled_;
-
   const int& width_;
 
   const int& height_;