On Thu, 2009-07-09 at 11:10 +0530, Mustafizur Rahaman wrote:
> Hi,
> 
> I am playing with OpenGL 2.0 on TI OMAP's 3430 ZOOM device with
> clutter. One of the surprising thing i noticed was when the hands are
> normally rotating, i am getting FPS of arouns 40, but if i just press
> my finger on the screen/stage area, the frame rate drops to 30FPS or
> even less, even though i am not doing anything on touch event.
> 
> I have a made gtk-clutter test app exactly similar to test-actor and
> there i am not listenning to any input event, still i see the same
> behavior. Does any one has seen similar behavior? Do we have anything
> in clutter itself that we intentionally drops the FPS, where there is
> any input event detected?

I'd guess what is happening is that your hand isn't completely still, so
when you are touching the screen, Clutter gets a constant stream of
motion events.

When a motion event is received between the two frames, then Clutter
will draw the scene twice:

 - Draw the scene in "pick mode", find the actor that should receive
   the event with glReadPixels()
 - Do the motion event
 - Draw the scene again

If you don't have excess graphics power available, then that may well
cause a frame rate drop.

- Owen


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