xserver 1.6 branch and mouse position zapping

Colin Guthrie gmane at colin.guthr.ie
Fri Dec 26 07:25:48 PST 2008

'Twas brillig, and Peter Hutterer at 26/12/08 00:25 did gyre and gimble:
> 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.

It's really hard to describe! Speed of movement doesn't seem to make 
much odds but I have narrowed down the behaviour to the "Snapping 
Windows" compiz plugin. Disabling this makes things a lot more stable 
but there are still some issues.

Every time I move the cube face, either with a window drag to the edge, 
or with a keystroke, the mouse pointer zaps to the top left.

I can't duplicate the behaviour in metacity, but I've not tried in Kwin4 

I'm not 100% certain it's a xserver issue here and perhaps compiz is 
hooking into something it shouldn't be, but it's certainly a regression 
of sorts.

Not really sure how to give you better info to help diagnose :(

I'll try asking on compiz IRC to see if anyone else is experiencing the 
same issues.

>> 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

Thanks Peter. The patck on #19086 appears to be working nicely for me.



Colin Guthrie

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