Cannot go back to higher resolution after setting virtual resolution

Binary package hint: gnome-control-center

The following happened to me today while attemping to use my laptop (compaq nc6220, intel 915 graphics) with a video projector. I attached the projector, opened the screen resolution capplet, selected the projector and turned its output on, and checked the "mirror screens" box. The highest common resolution was 1024x768. I pressed "apply".

The "virtual resolution" dialog appeared telling me that the virtual resolution had to be changed. That was surprising, since, up to this point, the laptop had been operating at 1280x1024. Since answering "no" here wouldn't apply the changes, and I had to do a presentation in a few minutes, I ended up accepting the change. After logging out and in again, everything worked as expected.

After the presentation, I disconnected the projector and tried to go back to my usual 1280x1024, but that resolution simply wasn't offered anymore, and a reboot didn't help to bring it back. Further inspection showed that the following lines had been inserted into my xorg.conf:

        SubSection "Display"
                Virtual 2304 1024
        EndSubSection

First, I wonder how the 2304 was calculated. Second, the capplet obviously won't offer any resolutions that don't fit into the virtual resolution. It should offer them, though, and should also offer to increase the virtual resolution accordingly. My workaround was to delete the lines from xorg.conf, but a less knowledgable user will be completely lost in this case.

This bug is probably related to bug #287062, but I decided to report that separately since it can be triggered in a different way. It is also clearly not the same as bug #224229.

I was using the capplet under intrepid beta (gnome-control-center 2.24.0.1).