lightdm - xrandr command to configure monitors only works once logged in - Ask Ubuntu

i have xrandr command sets monitors required (different scales deal ubuntu's extremely limited hdpi support @ current):

xrandr --fb 7040x2160 --output dp1 --mode 1920x1080 --pos 0x0 --scale 2x2 --output edp1 --mode 3200x1800 --pos 3840x180 --scale 1x1 

if run in terminal after logging in works perfectly. works via startup applications seen in these answers: 1, 2, , 3 (works without sleep). configuration looks this:

screen 0: minimum 8 x 8, current 7040 x 2160, maximum 32767 x 32767 edp1 connected primary 3200x1800+3840+180 (normal left inverted right x axis y axis) 294mm x 165mm    3200x1800     59.98*+  47.99      2880x1620     60.00      2560x1440     60.00      2048x1536     60.00      1920x1440     60.00      1856x1392     60.01      1792x1344     60.01      2048x1152     60.00      1920x1200     59.95      1920x1080     60.00    59.93      1600x1200     60.00      1680x1050     59.95    59.88      1600x1024     60.17      1400x1050     59.98      1600x900      60.00      1280x1024     60.02      1440x900      59.89      1280x960      60.00      1368x768      60.00      1360x768      59.80    59.96      1152x864      60.00      1280x720      60.00      1024x768      60.00      1024x576      60.00      960x540       60.00      800x600       60.32    56.25      864x486       60.00      640x480       59.94      720x405       60.00      640x360       60.00   dp1 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 531mm x 299mm    1920x1080     60.00*+  50.00    59.94      1920x1080i    60.00    50.00    59.94      1600x1200     60.00      1680x1050     59.88      1280x1024     75.02    60.02      1440x900      74.98    59.90      1280x960      60.00      1280x800      59.91      1152x864      75.00      1280x720      60.00    50.00    59.94      1024x768      75.03    70.07    60.00      832x624       74.55      800x600       72.19    75.00    60.32    56.25      720x576       50.00      720x480       60.00    59.94      640x480       75.00    72.81    66.67    60.00    59.94      720x400       70.08   dp2 disconnected (normal left inverted right x axis y axis) hdmi1 disconnected (normal left inverted right x axis y axis) hdmi2 disconnected (normal left inverted right x axis y axis) virtual1 disconnected (normal left inverted right x axis y axis) 

if run same command anywhere in startup process, either garbled configuration in framebuffer size incorrect (with screens placed on top of each other) or no effect @ all. places i've tried .xprofile, lightdm configuration (called display-setup-script, greeter-setup-script, , session-setup-script).

i've logged verbose output command, , time says it's set correct values, output on screens , querying xrandr afterwards says otherwise. how can configure screens further chain (at least greeter displayed correctly)? given x server initialised before then, there way xrandr configuration commands stick?

edit note: question focuses on root of problem "configuring monitors prior once logged in"

my guess during login process, unity tries set screen itself, might 1 of things breaks. if login screen doesn't require configuration, , needed unity session, consider adding command startup applications runs automatically after login. way unity applies changes, override them own command.

what recommend use modified version of command:

bash -c 'sleep 3 && xrandr --fb 7040x2160 --output dp1 --mode 1920x1080 --pos 0x0 --scale 2x2 --output edp1 --mode 3200x1800 --pos 3840x180 --scale 1x1' 

that way there's sufficient delay unity apply changes, , run own