State of Zaphod dual screen support

Simon Thum simon.thum at
Wed Mar 3 02:48:00 PST 2010

Peter Hutterer wrote:
> On Mon, Mar 01, 2010 at 12:41:02AM -0700, David Mohr wrote:
>> On Sun, Feb 28, 2010 at 11:37 PM, Peter Hutterer
>> <peter.hutterer at> wrote:
>>> On Sun, Feb 28, 2010 at 11:29:12PM -0700, David Mohr wrote:
>>>> I'm part of the minory who currently uses a Zaphod style dual monitor
>>>> setup with separate X screens for every monitor. When I recently
>>>> upgraded from 7.4 to 7.5, some utilites which I adopted[1] which
>>>> manipulate the mouse cursor started malfunctioning. My two X screens
>>>> are setup to be "apart" so that the mouse does not pass between them,
>>>> and I use my utilities to move the mouse between the two screens. But
>>>> with 7.5 every now and then a condition is triggered where the mouse
>>>> cursor will just continually jump from screen to screen, keeping the X
>>>> server at 100% CPU. I cannot even shut it down using
>>>> CTRL-ALT-Backspace.
>>>> I've noticed comments in other threads on this mailing list that
>>>> Zaphod mode is not really supported any more (for completeness' sake,
>>>> I'm using the binary Nvidia drivers). So my question is, is there
>>>> value in trying to track down the bug in Xorg which causes the mouse
>>>> to jump back and forth?
>>> yes. I've seen this myself and I have not yet identified the issue. it's a
>>> server bug and unrelated to the binary driver. If you can help track this
>>> issue down, it would be much appreciated.
>> Ok. Unfortunately I have not been able to find reliable conditions for
>> triggering the bug. I'll try again and see what I can find.
> i found using a wacom tablet with a xinerama setup and then switch back and
> forth triggers it eventually. the problem is the "eventually" bit...
I don't have an idea whether it's related, but maybe you can add code
which always clears the pointer's remainder fields, so 'eventually' may
become something more specific.

>> Is there any way to get good information out of the running X instance
>> once the bug has been triggered? I can only think of sending a signal
>> to get a core dump, but then I'm not sure how much useful information
>> that would contain.
> once it happens, gdb in and single-stepping may be the only approach. a
> backtrace would be great already, just to make sure if you're seeing the
> same problem as I am.
> Cheers,
>   Peter
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