[Freeglut-developer] FW: [OpenGLUT-devel] Re: Flooding the event queue with mouse moti on

[Fay J. F C. AAC/W. <joh...@eg...>]

Gentlemen,

	The gist of the e-mail chain below is, I think, that our OpenGLUT
brethren are looking into not processing window resize events that follow
one right after the other, and possibly not processing them until just
before a redraw.  I will keep us posted on how it turns out.  Before
recommending it for "freeglut," I would want to look at how GLUT handles it.

John F. Fay
joh...@eg...
850-729-6330 
-----Original Message-----
From: ope...@li...
[mailto:ope...@li...] On Behalf Of Nigel
Stewart
Sent: Thursday, April 21, 2005 8:42 PM
To: ope...@li...
Subject: Re: [OpenGLUT-devel] Re: Flooding the event queue with mouse motion

> In the words of Martin Luther, what does this mean?

	Good question!  I've been fiddling with the
	OpenGLUT event loop, with a particular view
	to opaque resize on KDE.  In this mode a
	steady stream of resize and expose events
	are sent to the window as the user adjusts
	the window size.  It's always looked a bit
	crappy in GLUT and FreeGLUT.

	Qt applications in particular, don't tend
	to flicker or tear the way OpenGLUT
	applications tend to.

	I came across this mouse motion handling,
	which seemed very much in line with
	collapsing mouse motion events.

	Overall, I think it is worth doing some
	additional queue manipulation in OpenGLUT
	due to the fact that when you actually
	trace all the events, it's no wonder that
	the queue can get flooded.

	For example, there is no point calling
	the resize callback if the very next
	event is another resize.  It doesn't
	serve the purpose of efficently draining
	the queue to call the same callback
	1000 times or so.

	In fact, I don't think a resize callback
	is needed until immediately before a
	draw.

Nigel

> ...
> 
>      if ( event->type == MotionNotify ) { // mouse move
>          if (event->xmotion.root != RootWindow(appDpy, x11Screen()) &&
>              ! qt_xdnd_dragging )
>              return FALSE;
> 
>          XMotionEvent lastMotion = event->xmotion;
>          while( XPending( appDpy ) )  { // compres mouse moves
>              XNextEvent( appDpy, &nextEvent );
>              if ( nextEvent.type == ConfigureNotify
>                   || nextEvent.type == PropertyNotify
>                   || nextEvent.type == Expose
>                   || nextEvent.type == NoExpose ) {
>                  qApp->x11ProcessEvent( &nextEvent );
>                  continue;
>              } else if ( nextEvent.type != MotionNotify ||
>                          nextEvent.xmotion.window != 
> event->xmotion.window ||
>                          nextEvent.xmotion.state != event->xmotion.state )
{
>                  XPutBackEvent( appDpy, &nextEvent );
>                  break;
>              }
>              if ( !qt_x11EventFilter(&nextEvent)
>                   && !x11Event( &nextEvent ) ) // send event through
filter
>                  lastMotion = nextEvent.xmotion;
>              else
>                  break;
>          }
>          type = QEvent::MouseMove;
>          pos.rx() = lastMotion.x;
>          pos.ry() = lastMotion.y;
>          globalPos.rx() = lastMotion.x_root;
>          globalPos.ry() = lastMotion.y_root;
> 
> ...


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