xserver 1.6 branch and mouse position zapping

[Peter Hutterer]

On Wed, Dec 24, 2008 at 11:41:10AM +0000, Colin Guthrie wrote:
> > Just built the 1.6 branch + recent mesa snapshot and other such stuff.
> > 
> > It seems to be stable enough just now, but one thing that's been 
> > affected is how the mouse positions itself to top-left after a certain 
> > operations.
> > 
> > So far I've found odd behaviour when doing:
> >   * Compiz cube dragging (ctrl+alt+click and drag)
> >   * Compiz window moving (alt+click and drag)
> >   * Compiz window moving (click and drag on title bar)
> > 
> > When this happens the mouse just jumps to the top left, but not always 
> > immediately.


> > While this could easily be a compiz issue (I certainly cannot reproduce 
> > in metacity), I'm guessing it's related to the xserver change. I have 
> > also updated to the latest input-proto and other such stuff too.
> > 
> > Is there an obvious starting point to look further into this? Or perhaps 
> > it's a known issue?

can you reproduce this with any other client too? It's most likely an X server
issue, but a good reproduceable behaviour in a client other than compiz makes
it easier for me to find the bug.
My first guess is that event replay after synchronous grabs have the wrong
coordinates.
You say it doesn't always happen immediately: try to move particularly fast or
slow to see if that can trigger it.
 
> I'm thinking that there is *something* up with mouse moves generally. 
> Simple things like hovering the mouse over a link in firefox is also a 
> bit odd. Hard to describe really but it seems that the "hover" event (in 
> web/js event terminology) only happens when the mouse is actually 
> *moving* not when it's just settled over the link.

A NotifyInferior event sent when moving the mouse from the menu bars into the
main window has the wrong subwindow information. This causes some internal
state in firefox to go nuts. Attributed to the wrong enter/leave model, see
also

http://lists.freedesktop.org/archives/xorg/2008-December/041696.html
http://bugs.freedesktop.org/show_bug.cgi?id=19086

Cheers,
  Peter