Laptop external screen resolution wrong

[J.A. Watson]

Binary package hint: xorg

Running on a Fujitsu Lifebook S6510, with a port replicator and an external Acer LCD display. Using 8.04.1 this was handled reasonably well; when booted with the external display connected, the initial resolution was 1280x1024, and when booted with only the laptop display, initial resolution was 1280x800. Using 8.10 Alpha-6, when booted with the external display connected the initial resolution is 1024x768 (when booting with only the laptop display the resolution is correct, 1280x800).

Examining the /var/log/Xorg.0.log file, I see that the server does in fact properly detect the Acer display, and reads the available modes, including 1280x1024. However, in the log file on 8.10 there is a line which reads:

/var/log/Xorg.0.log:(II) intel(0): Using fuzzy aspect match for initial modes

When the external display is not connected, the corresponding line in the log file reads:

/var/log/Xorg.0.log.old:(II) intel(0): Using exact sizes for initial modes

There is no such line in the log file under 8.04.1.

Also, when I try to adjust the screen resolution there are no values higher than 1024x768 listed.

Thanks.

ProblemType: Bug
Architecture: i386
DistroRelease: Ubuntu 8.10
Package: xorg 1:7.4~2ubuntu4
ProcEnviron:
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersion: Linux version 2.6.27-3-generic (buildd@vernadsky) (gcc version 4.3.2 (Ubuntu 4.3.2-1ubuntu6) ) #1 SMP Wed Sep 10 16:02:00 UTC 2008

SourcePackage: xorg
Uname: Linux 2.6.27-3-generic i686
xkbcomp:

[J.A. Watson (j-a-watson)]

I have done quite a bit more testing and experimentation with the Intrepid Beta release, and compared the way this works with Ubuntu Hardy Heron and Mandriva 2009 RC1. I think that what Intrepid is doing is very close to being "correct", and is considerably better than it was with Hardy.

- With and external display capable of 1280x1024 resolution connected, and the laptop display capable of 1280x800, by default Intrepid sets these two displays to "mirror", but with a maximum resolution of 1024x768. This is similar to what Hardy did, and what Mandriva does, except both of them offer 1280x1024 resolution, and then "clip" the image on the laptop display accordingly. Basically, the problem is that Intrepid not only doesn't choose a default resolution of 1280x1024 when the two displays are mirrored, but that it doesn't even off this resolution as an option in "mirrored" mode.

- If I remove "Mirror Screens" in the Monitor Resolution Settings, I am then able to select 1280x1024 on the external display, and 1280x800 on the laptop display, and I can change the relative positions of the two displays to anywhere around each other - but I still can't overlay them, as they would be if they were correctly "mirrored".

From this it appears to me that the problem is not with the detection, resolution or handling of the two displays, it is with the selection of the resolution when they are "mirrored".

jw

[Bryce Harrington (bryce)]

Hmm. I don't think this is actually an xserver bug.

If you look at your xrandr output, you can see that a wide range of resolutions have been properly detected. "Mirror" means that the system should use the highest resolution common to both displays, and you can see in the xrandr output that the only resolution higher than 1024x768 that the LVDS supports is 1280x800. The VGA doesn't support that mode, so 1024x768 is the highest resolution they can both display.

It's certainly possible to configure a "clipped" display like you describe with the xrandr command line tool, so both the things you describe in your previous comment can be done with Xorg. So maybe what you want to do is file a Wishlist bug against Screen Resolution (package gnome-control-center) to have such features added to the GUI.

[Andreas Schildbach (schildbach)]

Another solution would be to add quirks for the monitors that are obviously capable of displaying standard resolutions (in my case: 1280 x 768) but do not report these resolutions. Where would this need to be configured?

Whatever solution is chosen to resolve this regression, it should affect not only the current user but also GDM and the default of new users (e.g. guest session).