That's it. Fifo present mode halts until the next time the screen is refreshed. Mailbox will replace the lined up image if the refresh period has not been reached

src/main.rs

@@ -175,7 +175,8 @@ fn main() {
         //canvas.draw(&compu_sprite1);
         {
             let g = hprof::enter("Run");
-            (frame_future) = processor.run(&surface, frame_future,
+            processor.run(&surface,
+                                           //frame_future,
                                            canvas,
                                            compu_frame);
         }