GDM/Gnome confused about screen size

[Marius Gedminas]

On Thu, Jul 23, 2009 at 09:14:33AM +0100, Alex Bennee wrote:
> Since I finally got a working KMS build I have one final problem. GDM
> gets confused about what the screen size actually is. Although there
> is a display across the whole screen the menu bar and background image
> take up the top 3/4 of the screen.
>
> When Gnome starts it's menubars are both shorter and the bottom menu
> bar doesn't sit at the bottom of the physical screen. Interestingly if
> I drag the menu bar lower it actually expands it's width to fill the
> screen. I'm wondering if this is due to having my second monitor
> plugged in (but turned off) to the VGA port. xrandr reports:

Yes, GNOME is trying to make sure you can see both panels in both monitors.

> 09:07 alex at danny/x86_64 [linux-2.6-stable.git] >xrandr
> Screen 0: minimum 320 x 200, current 1680 x 1050, maximum 4096 x 4096
> VGA1 connected 1440x900+0+0 (normal left inverted right x axis y axis)
> 408mm x 255mm
>    1440x900       59.9*+
>    1280x1024      75.0
>    1024x768       75.1     70.1     60.0
>    832x624        74.6
>    800x600        72.2     75.0     60.3     56.2
>    640x480        72.8     75.0     66.7     60.0
>    720x400        70.1
> DVI1 connected 1680x1050+0+0 (normal left inverted right x axis y
> axis) 459mm x 296mm
>    1680x1050      59.9*+
>    1280x1024      75.0
>    1152x864       75.0
>    1024x768       75.1     70.1     60.0
>    832x624        74.6
>    800x600        72.2     75.0     60.3     56.2
>    640x480        72.8     75.0     66.7     60.0
>    720x400        70.1

Turn off VGA via the GNOME Display Preferences (or with xrandr -o VGA
--off) and GNOME will reposition the panels to align with the larger
remaining screen.

> I'm willing to raise a bug but I'm not sure what it should be against.
> Certainly both GDM and Gnome work fine when KMS is not enabled but is
> it likely their bug or with the X side of things? How does Gnome
> interrogate X to find out about these things?

It either uses the RANDR or Xinerama extension to learn about the
existence and position of various monitors.

> Any ideas?

Marius Gedminas
-- 
As a rule of thumb, I reckon Python to be an order of magnitude more wasteful
of CPU cycles and memory than my favourite low-level language, C++.
                -- Thomas Guest
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