Screen Resolution applet's Virtual line can break compiz

[michal kralik]

Binary package hint: compiz

Today I connected my Samsung 40" LCD to Thinkpad T60 and lost compiz too.

You connect external display, open screen resolution dialog which properly recognizes Samsung 40", enable it, configure resolution and hit apply.
Then it says, it has to edit the file directly to enable display.

Once applied, compiz is disabled, even the Normal visual effects don't work.
If you disconnect external display, reboot, compiz still doesn't work.
I noticed there is backup of my /etc/X11/xorg.conf. Here is the diff

21,24d20
< Section "Device"
< Identifier "Configured Video Device"
< EndSection
<
32a29,31
> SubSection "Display"
> Virtual 2760 1050
> EndSubSection
33a33,37
>
> Section "Device"
> Identifier "Configured Video Device"
> EndSection
>

I replaced the xorg.conf with backed up and it all works fine.

Ubuntu 8.10
uname -a: Linux ninjacat 2.6.27-11-generic #1 SMP Thu Jan 29 19:24:39 UTC 2009 i686 GNU/Linux
compiz version: 0.7.8

[michal kralik (ceecko)]

lspci
00:02.0 VGA compatible controller: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller (rev 03)
00:02.1 Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03)

[Chris Halse Rogers (raof)]

 affects ubuntu/compiz
 status invalid

 affects ubuntu/gnome-control-center
 importance wishlist
 status confirmed
 summary "Screen Resolution applet's Virtual line can break compiz"

So, this isn't a compiz bug. The problem is that your Intel card can't
do DRI with a framebuffer (total display resolution of all monitors
combined) greater than 2048 in either dimension. Since the combined
x-resolution of your two screens is 2760, you're hitting this limit.

Opening a task against gnome-control centre (where the Screen Resolution
capplet lives). It would be nice if the capplet could mention this when
writing the Virtual (framebuffer size) line to your Xorg.conf.
Something like "This hardware/driver does not support 3D with a screen
size > 2048x2048. Enabling this monitor would expand the screen size to
$BAR. Do you want to continue", sort of thing.

[michal kralik (ceecko)]

Thank you,

please note also that disabling the external display, returning back to "normal" resolution doesn't solve the problem.
User has to manually replace xorg.conf, or remove the Virtual section.

[Sebastien Bacher (seb128)]

reassigning to screen-resolution-extra which does this change

[Chris Halse Rogers (raof)]

This is no longer valid; we (a) no longer ship screen-resolution-extra, and (b) the X server no longer requires a Virtual line to handle dual-head properly.