On 2022-01-20 13:59:21 +0100, Vincent Lefevre wrote: > The second point is that there is a race condition in the detection of > the monitors on startup, so that the behavior varies. > > This issue is actually also now reproducible with systemd 250.2, but > the systemd version seems to have an effect of the possible behaviors > (A, B and C below): > > With systemd 250.2: > A. 2 monitors detected, the greeter appears. > B. 2 monitors detected, the greeter does not appear. > > With systemd 250.3: > B. 2 monitors detected, the greeter does not appear. > C. 1 monitor detected (the laptop screen), the greeter appears on > this monitor. > > Case C is actually like a one-monitor setup (it could occur in the > past, perhaps still currently with systemd 250.2, but I haven't > done many tests with this version, mainly focusing on 250.3). > Note that when 2 monitors are detected, they are always mirrored. > > Case B has never appeared before (I was always in case A or C), > while my monitor setup hasn't changed. 2 things have changed on > my laptop in the last few days: [...]
I now have a better workaround than setting active-monitor=1 (which has issues with the menu as I've said, perhaps because the knowledge of lightdm about the connected monitors and their configuration is inconsistent due to the race condition): delay the setup in order to avoid the race condition. Adding a script /etc/lightdm/display-setup-script with "sleep 1" and setting display-setup-script=/etc/lightdm/display-setup-script in /etc/lightdm/lightdm.conf seems to solve the problem. Note: this does not have any effect on the detected monitors, i.e. one may still have randomly 1 or 2 detected monitors[*], but in the case of 2 detected monitors, the greeter is visible. [*] This is probably taken into account when lightdm starts X (which occurs before, as seen in the lightdm.log debug log). If one wants to fix that, one could do that with xrandr (not tested). In short, even though there is a good workaround, the greeter should do its best to display its menu bar and dialogs at a position where there will be visible. Finally, I don't know about the other greeters, but if they have a similar issue, this workaround should also work since it is on the lightdm level. -- Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
