[ubuntu-x] Default behaviour for dual head with different resolutions

[Geir Ove Myhr]

Hi everyone,

I have seen this happen for the -intel driver, but I'm not sure if
this is specific to that or if it is a change that happened somewhere
else in xorg:

Somewhere between Hardy and Intrepid the behaviour for two different
mirrored monitors in a dual-head setup changed. In Hardy both monitors
would use their native resolution, but the "Desktop size" would be
limited to what both monitors could show. A screenshot of the login
screen is at [1] and a screenshot of the desktop is at [2]. From
Intrepid on, the resolution has been set to the lowest that both
monitors could handle which sometimes would lead to one of the
monitors using its native resolution and sometimes both would use a
lower one. I actually liked the old behaviour better, and so does the
reporters of bugs [3] and [4]. Of course it would be even better if
the "active" desktop area was centered on the monitor instead of being
located in the upper left corner.

With KMS the current behaviour is even more unfortunate, since one of
its advantages is fewer mode changes. Currently, the monitors are
assigned their native resolution on boot and then changes to the lower
resolution once gdm starts. If the monitors are set up to be used with
an extended desktop the mode changes again when the user logs in.

1. In which xorg component did this change occur?
2. Is there any record of the rationale behind this change?
3. What do you think would be the proper behaviour?

[1] http://launchpadlibrarian.net/17844487/importdump.jpg
[2] http://launchpadlibrarian.net/12354400/screen.png
[3] https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/286001
[4] https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/404919