Created attachment 26141 [details] Xorg configuration file GDM displays its login box on the wrong monitor ("wrong" in the sense that it's not what I want.) It seems that there are three things that may influence this: the display geometry and arrangement, xrandr CRTC ordering, or xinerama screen ordering. I'm not at all clear on what the last two are about, or their relationship to one another. I'm assuming that the xrandr CRTC ordering is the way to go. I've looked around extensively and there seems to be no way to modify xorg.conf in order to specify the xrandr primary output. This is the default configuration: rah@myrtle:~$ xrandr --verbose -q | egrep 'DVI-[[:digit:]] connected|CRTC' DVI-1 connected 1920x1200+1280+0 (0x4d) normal (normal left inverted right x axis y axis) 519mm x 324mm CRTC: 1 CRTCs: 0 1 DVI-0 connected 1280x1024+0+0 (0x4f) normal (normal left inverted right x axis y axis) 380mm x 300mm CRTC: 0 CRTCs: 0 1 I have added the following to /etc/gdm/Init/Default: xrandr --output DVI-1 --primary this changes the configuration to: rah@myrtle:~$ xrandr --verbose -q | egrep 'DVI-[[:digit:]] connected|CRTC' DVI-1 connected 1920x1200+1280+0 (0x4d) normal (normal left inverted right x axis y axis) 519mm x 324mm CRTC: 0 CRTCs: 1 0 DVI-0 connected 1280x1024+0+0 (0x4f) normal (normal left inverted right x axis y axis) 380mm x 300mm CRTC: 1 CRTCs: 1 0 I presume that this should be enough for GDM to but it's evidently not as the login box still displays on the wrong monitor. This could be a bug in GDM but it highlights the fact that there is no way to specify the primary output in xorg.conf, and that definitely seems like a bug in X.
Created attachment 26142 [details] Xorg log
(In reply to comment #0) > DVI-1 connected 1920x1200+1280+0 (0x4d) normal (normal left inverted right x > axis y axis) 519mm x 324mm > CRTC: 1 > CRTCs: 0 1 > xrandr --output DVI-1 --primary > DVI-1 connected 1920x1200+1280+0 (0x4d) normal (normal left inverted right x > axis y axis) 519mm x 324mm > CRTC: 0 > CRTCs: 1 0 Looking at this output more closely, the issue is obviously with the "CRTCs:" line. Running "xrandr ... --primary" evidently does not change the order of the CRTCs (and nor is there a way to specify it in xorg.conf.)
The same is true for at least KDM and XDM, it is not a GDM issue. The problem is that the radeon driver and others as well always use the left most monitor for displaying the login screen, it is not the "first" one in the sense of connectors. In contrast the radeonhd driver seems to do this by connector and uses the monitor that is connected to the "proposed" primary connector. In most cases this will be DVI-0. The behavior of radeon in this case should really be fixed. For multihead (using multiple monitors for the "desktop") this would just be a nice-to-have but for those using other connectors for e.g. TV or beamer output it should be configurable somehow. Of course there is always the "workaround" of just changing the position of the monitors inside the large virtual screen so that the monitor that should get the login screen is on the left but what if you like to have the login on the middle monitor in a three-seat environment (latest Radeon HD 5XXX support up to three separate displays per card)?
Mass closure: This bug has been untouched for more than six years, and is not obviously still valid. Please file a new report if you continue to experience issues with a current server.
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