gpd-display-scaler rescales any 1920x1200 display, not just the internal panel

[alexmbird]

Steps to reproduce:

• GPD Pocket 2 (amber black in this case)
• External 1920x1200 HDMI display connected via adapter. I have mine set as primary but doubt that makes a difference.
• Reboot, login and let gpd-display-scaler run
• Marvel at the comically big fonts on your external monitor :(

Looking at the output of xrandr it seems the Pocket's internal display is always listed as eDP1 and the external is always DP1.

A second, possibly-related problem sometimes occurs when I disconnect then reconnect the HDMI monitor. It starts out at 1:1 scaling but upon reconnection is set to the same 0.64x0.64 as the built-in panel. If the DP1 and eDP1 names are static it might therefore make sense to reset it whenever gpd-display-scaler runs.

My "fixed" script looks like:

# If internal display is present & set to high res, scale it
if [ xrandr | egrep --quiet "^eDP1 connected" ]; then
  if [ "${PANEL_RESOLUTION}" == "1920x1200" ]; then
    xrandr --output eDP1 --scale 0.64x0.64
  fi
fi

# (re)set external display as 1x1 as scale can be forgotten upon reconnect
if [ xrandr | egrep --quiet "^DP1 connected" ]; then
  xrandr --output DP1 --scale 1x1
fi

The check for eDP1 being 1920x1200 might now be superfluous. I can't think of any situations where it would be running at another res where scaling isn't desired, but maybe I'm missing somebody else's use case.

I'd submit this as a PR but I don't have any other GPD Pockets to test it on so my assumption about monitor names may be flawed. Best if somebody with access to more devices can test it first.