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I have a custom xrandr script which enables my external monitors and disables my laptop's monitor. When I disconnect my external monitor, I can't enable the monitor because my screen is blank.

I'd love to be able to access my console tty (ctrl-alt-f1), and trigger xrandr to go on (i.e. xrandr --output eDP1 --auto). Running that in my tty says "Can't open display". Any tips for how I can do that?

Jacob Vlijm
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Justin Abrahms
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1 Answers1

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No need to go into console, you could achieve the same by adding a custom keyboard shortcut to re- enable your internal screen.

Choose System Settings > Keyboard > Shortcuts > Custom Shortcuts, click the + and add the command to a shortcut of your choice:

xrandr --output <screenname> --auto

Just tested it on my system (laptop, 15.10); switched off my screen and successfully re- enabled it with the keyboard shortcut, running the command :)

Alternatively

You could use an edited version of this script. The version below (small background script, is checking once per four seconds if an external screen is connected) makes sure your internal screen is switched on

#!/usr/bin/env python3
import subprocess
import time
# --- set your internal screen below (the example is my primary screen)
internal = "DVI-I-1"
#---

# don't change anything below
scr_info1 = 0

while True:
    time.sleep(4)
    # read the current screen setup from xrandr
    get_screens = subprocess.check_output("xrandr").decode("utf-8").splitlines()
    scr_data = [l for l in get_screens if " connected " in l]
    # count the number of connected screens
    scr_info2  = len(scr_data)
    # if the number of connected screens changes, 
    # switch off the internal one if there are two screens
    if scr_info2 != scr_info1:
        if scr_info2 == 2:
            ext = [s.split()[0] for s in scr_data if not internal in s][0]
            subprocess.Popen(["xrandr", "--output", internal, "--off", "--output", ext, "--auto"])
        else:
            subprocess.Popen(["xrandr", "--output", internal, "--auto"])

    scr_info1 = scr_info2

How to setup

  1. Copy the script above into an empty file, save it as switch_screens.py
  2. In the head section of your script, set the name of your internal screen. To find out, open a terminal window and run the command xrandr (no external screen connected) The line with "connected" in it shows the name of your screen in the first string, looking like: VGA-1 or something like that.

  3. Test- run it by opening a terminal window and typ the command:

    python3 /path/to/switch_screens.py

    While the script runs, connect your external screen, wait for you internal screen to switch of and disconnect again.

  4. If all works fine, add the command below to Startup Applications: open Dash > Startup Applications > Add. Add the command:

    /bin/bash -c "sleep 15 && python3 /path/to/switch_screens.py"

Log out and back in. Now your internal screen is switched off automatically if an external screen is connected, re- enabling it if you disconnect.

The script adds no noticeable burden at all to your system.

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Jacob Vlijm
  • 85,475