External monitor on Linux

Aug 12, 2019

1. On each connect

Short command to set the correct resolution and scaling for an external monitor.
I've decided to write this down because the --scale-from parameter seems to be uncommon. Most suggestions on the internet only use --scale, which I find less intuitive to use.

# XPS 13 with full hd display
xrandr --output DP1 --primary --mode 1920x1080 --scale-from 1920x1080 --same-as eDP1
# XPS 15 with 4k display on an external WQHD display
xrandr --output DP1 --primary --mode 2560x1440 --scale-from 3840x2160 --same-as eDP1

2. Automate it by using autorandr

sudo pacman -S autorandr
sudo systemctl enable --now autorandr.service

I've created two profiles.

First, I connect no external monitor.
Then I run autorandr --save default.
Next, connect the external monitor.
Run the fitting xrandr command above. Check everything looks nice.
Run autorandr --save docked.

autorandr should switch to the correct mode automatically (hence the name) from now on.

What's neat: If you close the lid while the notebook is connected to the external monitor, it doesn't go into sleep mode.

Problems with autorandr

I now had two different laptops where autorandr caused problems. After connecting to a screen I had no output (not even on the laptop screen) and xrandr commands were "ignored": It returned immediately, but didn't change anything.

I don't know a good alternative, so I will keep custom xrandr scripts for my different displays. :(

I might try xlayoutdisplay in future, although it works a bit differently.

Update: This doesn't seem to be a problem of autorandr, but rather some display driver issue, even though I've experienced this issue on two different devices. I had the same problem with autorandr uninstalled and using xrandr directly now.