I have a weird issues that has been bothering me for a week or two.

  • I have two accounts on a Xubuntu 18.04 (recently updated)
  • When I log in either of thoses accounts, screen resolution is working perfectly (on login screen too)
  • If I "lock screen" (that is, just going back to login w/o logging out), screen stops being recognized and uses a very small resolution. This bug affect the login screen AND the other account.
  • If I go back to the first connected account, screen still works perfectly.
  • If I log out from the first account (instead of using "lock screen"), there is no bug

Any idea what could be causing this ? I've search on google but to no avail so far.

Thanks !

EDIT: it seems the screen stops being recognized altogether when the bug happens.

BEFORE the bug :

~ xrandr             
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
DVI-I-0 disconnected (normal left inverted right x axis y axis)
DVI-I-1 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 299mm
   1920x1080     60.00*+  59.99    59.94    50.00    60.05    60.00    50.04  
   1680x1050     59.95  
   1600x1200     60.00  
   1440x900      59.89  
   1366x768      59.79  
   1280x1024     75.02    60.02  
   1280x960      60.00  
   1280x720      60.00    59.94    50.00  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   800x600       75.00    72.19    60.32    56.25  
   720x576       50.00  
   720x480       59.94  
   640x480       75.00    72.81    59.94    59.93  
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DVI-D-0 disconnected (normal left inverted right x axis y axis)

AFTER the bug :

~ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 480, current 640 x 480, maximum 640 x 480
default connected 640x480+0+0 0mm x 0mm
   640x480       73.00* 

I had the same issue on Ubuntu 18.04 with GNOME. check the monitors.xml file for inconsistencies. I had two times the "same" monitor listed with different settings. Delete everything except for one.

nano .config/monitors.xml

my file looks like this now:

<monitors version="2">
          <product>DELL U2515H</product>

I hope this helps.

  • Xfce doesn't seem to use .config/monitors.xml. I tried what would be the equivalent ($HOME/.config/xfce4/xfconf/xfce-perchannel-xml/display.xml) but no issue in this file :( – Stoh Jul 10 '18 at 7:51

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