Triple monitor, one card; xrandr => xorg.conf

[Alex Deucher]

On Wed, May 29, 2013 at 1:20 AM, Nick Urbanik <nicku at nicku.org> wrote:
> Dear Alex,
>
> Thank you so much for taking the time to make a thoughtful reply.
>
> On 29/05/13 00:21 -0400, Alex Deucher wrote:
>>
>> On Sat, May 25, 2013 at 9:00 AM, Nick Urbanik <nicku at nicku.org> wrote:
>> You can skip the above lines if you just change the monitor
>> identifiers to match your output names.  Also, I'm not sure that
>> having relative locations for every monitor will work correctly.  For
>> the farthest left one, leave out the orientation.
>>
>>> EndSection
>>
>>
>> Try something like this:
>>
>>
>> Section "Device"
>>  Identifier "ati-5450"
>> EndSection
>>
>> Section "Monitor"
>>   Identifier "DVI-0"
>> EndSection
>>
>> Section "Monitor"
>>   Identifier "DisplayPort-0"
>>   Option "RightOf" "DVI-0"
>> EndSection
>
>
> Yes, that works for when lightdm starts: the screens are in the right
> order.  Its simplicity is beautiful (the xorg.conf you wrote).
>
> But when I log into XFCE 4.10, then it does as described in my last
> post on this topic: VGA-0 on the left, then DVI-0, then at 1900 pixels
> from the left of VGA-0, which takes us into the territory of DVI-0,
> then DisplayPort-0 continues, mirroring DVI-0 for all but 150 pixels
> on the left and 150 on the right.  Is it XFCE being naughty?
>
> As before, my xrandr command makes everything pop into the right place
> and behave properly, but I'd like to have things "just work".
>
> As a probably unrelated side issue, neither gdm nor Gnome 3 start up,
> regardless of presence or shape of xorg.conf.

If X comes up ok without a display manager or desktop environment,
your config should be working fine.  Different display managers and
desktop environments try and remember your display configuration in
various ways and I suspect you are running into issues with them
conflicting with your xorg.conf.  If there is a monitor config gui for
your desktop environment, I'd suggest removing your xorg.conf and
using the gui to set up and remember your monitor configuration.
Hopefully that should use the desktop specific mechanisms to remember
your configuration.

Alex