(oneiric) greeter screen displayed incorrectly with external monitor during login

[Jane Silber]

I am running up to date (as of 15 Sept) Oneirc beta on a laptop with an external monitor. When booting with the monitor plugged in, I see the following:

- what appears to be the default greeter/sign in screen displayed correctly for a second or two
- a white flash
- that same sign in screen re-displayed but this time it is only in the top 2/3 of the laptop screen, with the bottom third of that screen blank.

It works (i.e., I can log in), but looks shoddy.

[Jane Silber (silbs)]

Photographic evidence.... :)

http://ubuntuone.com/2mtu72aL9iryaLmhUoqp9x - the login screen when external monitor is attached. When there is no external monitor, it appropriately files the whole screen

http://ubuntuone.com/0bTzkojNHiO3AYwKcoJVV6 - the external monitor during login (i.e., after entering password, before getting to desktop)

http://ubuntuone.com/2JOne4QI2c0PsaTVHgSm5k - the laptop screen during login (i.e,. after entering password, before getting to desktop)

[Bryce Harrington (bryce)]

Hi Jane,

Actually the three photos represent (at least) two distinct bugs. The first one was a lightdm problem which we believe is now resolved. This bug was originally just marked a dupe of that issue.

The other two, where you see some improperly drawn screen temporarily during the login process, are still relevant issues that need further investigation. I am unduping this bug so we can focus on those problems.

[Bryce Harrington (bryce)]

Essentially, the problem is that during login the screen resolution is resized but the screen isn't cleared; gnome-settings-daemon (or *possibly the GPU) just fills the undefined space with snippets from the framebuffer.

We could just insert a blank before beginning the login, and then unblank after, however this would cause an undesirable flicker for normal cases, where the screen resolution does not need to be changed.

Perhaps a better approach would be to alter gnome-settings-daemon such that when it does a mode change during login, to either blank or scale the existing framebuffer, rather than the ugly tiling.

[Bryce Harrington (bryce)]

Adding design team, because the decision about whether to blank, tile, or scale for the transition between login session and user session when resolutions don't match will require design team input.

[Bryce Harrington (bryce)]

Added bug to multi-monitor specification.
https://blueprints.launchpad.net/ubuntu/+spec/desktop-p-multi-monitor

[Bryce Harrington (bryce)]

Confirmed still affecting precise. Still awaiting word from Design.

[Stewart Wilson (stewartw)]

Hi Bryce,

As a temporary solution for Precise, can we please blank the framebuffer in the transition between the login session and the user session, where the display resolutions do not match.

Going forwards, we will display login screens on each display at their native/last-used resolutions:
See related bug: https://bugs.launchpad.net/ubuntu/+source/unity/+bug/924759
See multi-monitor spec: https://docs.google.com/a/canonical.com/document/d/1aHvJ-iIw-59bXTYBmIhQqEx0za2h9jpFE_RhZ2VOvJc/edit#bookmark=id.48eaevlgunt0

Upon login, it is then planned to use a cross-fade transition between the login session and user session.

[Robert Ancell (robert-ancell)]

Unity Greeter 0.2.2 now understands multi-monitors so I'd expect the layout to be more correct (please confirm Jane when it hits the archive). But it only uses the default behaviour that X/gnome-settings-daemon chooses which is mirror on my system. This is fine for first login but once the user changes their session to span monitors then there is the mismatch.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Christian González (droetker)]

I have the same problem here. As additional hint: During my user session, my monitors are layouted correctly (Laptop monitor right, external left, as configured in Unity Control Center), but lightdm doesn't respect that (as ~/.config/monitors.xml isn't read by lightdm I suppose), so during login the external monitor is on the right.

The display resolutions are the same during login and user session.

This seems to lead to the problem that the display buffer needs to change because the monitors are going to be switched. Could it "solve" (optically) the problem if lightdm would just accept the multi monitor setting of the user?

This seems to need another setting in Unity Control Center/Display like "Use this settings for login screen" (needs to be "unlocked" like in user settings too).