I usually connect an external display to my laptop. Since I do not have an inverter at my home, whenever the electricity goes off, I cannot use my external display. In that case, I cannot view the windows that are there on the external display. In order for those to be visible on the laptop's screen, I have to disconnect the HDMI cable from my laptop.
Usually there won't be much of power outages in my area. Even if it is there, it will come back with in a few minutes. In those instances, rather than disconnecting the HDMI cable, I prefer to take rest till electricity come back. If I was working on anything interesting, I would disconnect the HDMI and work in my laptop.
But, recently due to heavy rainfall, the frequency of power outages increased in my area. So, either I have to take complete rest or I have to keep on connecting and disconnecting the HDMI cable. I cannot opt for the first option because I have to pay my bills 😜. So, I started searching for ways to reduce the effort of doing the second option.
I came across a tool called xrandr which can be used to set the size, orientation or reflection of the outputs for a screen. I found that this tool can also be used to disable and enable the displays. That's what I wanted.
Running xrandr without any arguments will show the current state of all the display devices. Here's the output of xrandr command:
Screen 0: minimum 320 x 200, current 3926 x 1440, maximum 16384 x 16384
eDP-1 connected 1366x768+2560+472 (normal left inverted right x axis y axis) 309mm x 173mm
1366x768 60.00*+
1360x768 59.80 59.96
1280x720 60.00 59.99 59.86 59.74
1024x768 60.04 60.00
960x720 60.00
928x696 60.05
896x672 60.01
1024x576 59.95 59.96 59.90 59.82
960x600 59.93 60.00
960x540 59.96 59.99 59.63 59.82
800x600 60.00 60.32 56.25
840x525 60.01 59.88
864x486 59.92 59.57
800x512 60.17
700x525 59.98
800x450 59.95 59.82
640x512 60.02
720x450 59.89
700x450 59.96 59.88
640x480 60.00 59.94
720x405 59.51 58.99
684x384 59.88 59.85
680x384 59.80 59.96
640x400 59.88 59.98
576x432 60.06
640x360 59.86 59.83 59.84 59.32
512x384 60.00
512x288 60.00 59.92
480x270 59.63 59.82
400x300 60.32 56.34
432x243 59.92 59.57
320x240 60.05
360x202 59.51 59.13
320x180 59.84 59.32
HDMI-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
2560x1440 59.95*+
1920x1080 60.00 50.00 59.94
1680x1050 59.88
1600x900 60.00
1280x1024 75.02 60.02
1440x900 59.90
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
This shows that we've two output display devices named eDP-1 (laptop's screen) and HDMI-1 (external display). Also it shows other information such as the available resolutions and currently active resolution etc.
We can disable any output by making use of --off flag. For example, if I wanted to disable HDMI-1 output:
xrandr --output HDMI-1 --off
To enable the output, we can make use of --auto flag. To make one display as the primary display, we can make use of --primary flag. If I wanted to enable both displays and make the external display as the primary one, I can make use of the following command:
xrandr \
--output HDMI-1 --primary --auto \
--output eDP-1 --auto
Yes. You can configure multiple displays in a single command.
My use case was to toggle HDMI display. That involves checking whether the display is already disabled or not.
I searched a lot and couldn't find a way to do this. Then, while looking at the xrandr output, I found that for the enabled output, it will show the resolution along with the 'connected' information. ex:
eDP-1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 173mm
To check whether HDMI-1 is enabled, I can make use of grep to do some pattern matching.
xrandr | grep "HDMI-1 connected" | grep -Pq "\\dx\\d";
#!/bin/sh
if xrandr | grep "HDMI-1 connected" | grep -Pq "\\dx\\d"; then
xrandr \
--output eDP-1 --auto --primary \
--output HDMI-1 --off
else
xrandr \
--output HDMI-1 --primary --auto \
--output eDP-1 --auto --right-of HDMI-1
fi
I saved this script in a location and using the keyboard shortcut manager I created a keyboard shortcut (Mod+0) to call this script.
Now, whenever the power goes or comes, instead of physically disconnecting or connecting HDMI cable, I just need to press Mod (windows key) + 0 🤷♂️