If the sync flag is set in GraphicsWindow, end_frame flushes the pipe,

but doesn't swap buffers.  To swap buffers, call GraphicsWindow.swap()

panda/src/display/graphicsWindow.I

@@ -288,3 +288,26 @@ get_button_event(int device) {
   return _input_devices[device].get_button_event();
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: GraphicsWindow::set_sync
+//       Access: Public
+//  Description: Sets flag for whether the buffer swap is done 
+//               implicitely at the end of each frame, or done
+//               explicitely for the purpose of synchronization.
+////////////////////////////////////////////////////////////////////
+INLINE void GraphicsWindow::
+set_sync(const bool b) {
+  _is_synced = b;
+}
+
+////////////////////////////////////////////////////////////////////
+//     Function: GraphicsWindow::get_sync
+//       Access: Public
+//  Description: Returns whether buffer swap is done explicitely by
+//               call to swap() method.
+////////////////////////////////////////////////////////////////////
+INLINE bool GraphicsWindow::
+get_sync() const {
+  return _is_synced;
+}
+

panda/src/display/graphicsWindow.cxx

@@ -140,6 +140,7 @@ GraphicsWindow(GraphicsPipe *pipe) : Configurable() {
   _idle_callback = NULL;
   _resize_callback = NULL;
   _frame_number = 0;
+  _is_synced = false;
 }
 
 ////////////////////////////////////////////////////////////////////
@@ -157,6 +158,7 @@ GraphicsWindow(GraphicsPipe *pipe,
   _draw_callback = NULL;
   _idle_callback = NULL;
   _resize_callback = NULL;
+  _is_synced = false;
 }
 
 ////////////////////////////////////////////////////////////////////
@@ -601,6 +603,16 @@ void GraphicsWindow::read_priorities(void) {
   }
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: GraphicsWindow::swap
+//       Access: Public
+//  Description: Swaps buffers explicitely as synchronization 
+//               mechanism. 
+////////////////////////////////////////////////////////////////////
+void GraphicsWindow::
+swap() {
+}
+
 void GraphicsWindow::deactivate_window(void) { return; }
 void GraphicsWindow::reactivate_window(void) { return; }
 

panda/src/display/graphicsWindow.h

@@ -121,6 +121,11 @@ PUBLISHED:
   INLINE void set_frame_number(const int);
   INLINE int get_frame_number() const;
 
+  INLINE void set_sync(const bool);
+  INLINE bool get_sync() const;
+
+  virtual void swap();
+
 public:
   virtual void resized(const int, const int);
 
@@ -196,6 +201,8 @@ protected:
   vfnii _resize_function;
   int _frame_number;
 
+  bool _is_synced;
+
 protected:
 
   Callback *_draw_callback;

panda/src/glxdisplay/glxGraphicsWindow.cxx

@@ -673,12 +673,18 @@ void glxGraphicsWindow::end_frame( void )
 
   {
     PStatTimer timer(_swap_pcollector);
-    glXSwapBuffers(_display, _xwindow);
+    if(_is_synced)glFinish();
+    else glXSwapBuffers(_display, _xwindow);
   }
 
   GraphicsWindow::end_frame();
 }
 
+void glxGraphicsWindow::swap()
+{
+    if(_is_synced) glXSwapBuffers(_display, _xwindow);
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: handle_reshape
 //       Access:

panda/src/glxdisplay/glxGraphicsWindow.h

@@ -55,6 +55,8 @@ public:
   virtual void update(void);
   virtual void end_frame( void );
 
+  virtual void swap(void);
+
   INLINE Window get_xwindow(void) { return _xwindow; }
 
   virtual TypeHandle get_gsg_type() const;

panda/src/wgldisplay/wglGraphicsWindow.cxx

@@ -1022,11 +1022,21 @@ void wglGraphicsWindow::end_frame(void) {
 
   {
     PStatTimer timer(_swap_pcollector);
-    SwapBuffers(_hdc);
+	 if(_is_synced) glFinish();
+	 else SwapBuffers(_hdc);
   }
   GraphicsWindow::end_frame();
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: swap
+//       Access:
+//  Description: Swaps the front and back buffers explicitly.
+////////////////////////////////////////////////////////////////////
+void wglGraphicsWindow::swap(void) {
+    if(_is_synced)SwapBuffers(_hdc);
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: handle_reshape
 //       Access:

panda/src/wgldisplay/wglGraphicsWindow.h

@@ -66,6 +66,7 @@ public:
   virtual bool supports_update() const;
   virtual void update(void);
   virtual void end_frame( void );
+  virtual void swap( void );
 
   virtual TypeHandle get_gsg_type() const;
   static GraphicsWindow* make_wglGraphicsWindow(const FactoryParams &params);