blank screen after external HDMI monitor switch back to laptop

Problems with hardware & laptops not being detected or supported during or after install.
mybrid
Posts: 1
Joined: Fri Mar 29, 2019 3:26 pm

blank screen after external HDMI monitor switch back to laptop

Postby mybrid » Fri Mar 29, 2019 3:39 pm

Hi!

I use my laptop to watch TV. This means I plug in an external HDMI monitor and turn off my laptop display. After I was done watching I unplugged the HDMI cable and closed the laptop lid. When I opened up the laptop the next morning then after I logged in I got a blank screen until I plugged in the external monitor again.

It took me three hours to figure this out because searching the web these days is terrible, bad google, and documentation is poor.

1. lxrandr man page does not specify the save configuration file used. Here it is:
.config/autostart/lxrandr-autostart.desktop
2. I searched on all kinds of "LXDE blank screen" and came up with just installation and hardware issues.
3. sudo xrandr would come back with "Can't open display" when I used 'Cntr-Alt-F1' to get console. So I could not reset manually.
4. lxrandr is just a gui for xrandr, no help.

I keep a previous day backup on an external drive. I diffed all the files under ~/.config until I came up with this:

GOOD:
2019-03-29 11:20:28 % cat .config/autostart/lxrandr-autostart.desktop
[Desktop Entry]
Type=Application
Name=LXRandR autostart
Comment=Start xrandr with settings done in LXRandR
Exec=sh -c 'xrandr --output eDP-1-1 --mode 1920x1080'
OnlyShowIn=LXDE

BAD:
2019-03-29 11:21:26 % cat /1tb/ffh/snapshot/home/mybridlocal/.config/autostart/lxrandr-autostart.desktop
[Desktop Entry]
Type=Application
Name=LXRandR autostart
Comment=Start xrandr with settings done in LXRandR
Exec=sh -c 'xrandr --output eDP-1-1 --off --output DP-1 --auto --same-as eDP-1-1'
OnlyShowIn=LXDE

I fixed the problem by deleting .config/autostart/lxrandr-autostart.desktop and performing a "Save" in lxrandr.

If you are having problem switching monitors and logging back in then remove this file and recreate it using lxrandr.

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