make mirroring displays the default in gnome

Question

I use gnome with multiple displays. I use these in a mirroring setup. However, whenever my external display reconnects (whether by plugging in or by powering on the display), it seems to forget that i preferred for it to mirror.

Is there any way i can set this as the default somehow?

Answer 1

When an external display connect, we need to trigger a shell script We can do this by using udev

First, if you don't have udev on your Ubuntu

Run the following command:

sudo apt install udev

Monitor (output) UDEV events with udevadm

This step will be most important for each user. Run udevadm monitor --environment --udev. Then connect your HDMI cable.

udev rule

Based on the output from the above command, the user created this udev rule at /etc/udev/rules.d/95-monitor-hotplug.rules.

KERNEL=="card0", SUBSYSTEM=="drm", ENV{DISPLAY}=":0", ENV{XAUTHORITY}="/home/YOUR_USER_NAME_GOES_HERE/.Xauthority", RUN+="/usr/local/bin/hotplug_monitor.sh"

Where YOUR_USER_NAME_GOES_HERE is your username.

You may want to adjust the xrandr options to suit your needs.

First run xrandr to detect your current screens:

$ xrandr
Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 8192 x 8192
LVDS1 connected (normal left inverted right x axis y axis)
   1600x900       60.0*+   40.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9
HDMI3 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 521mm x 293mm
   1920x1080      60.0*+
   1600x1200      60.0  
   1680x1050      59.9  
   1680x945       60.0
   [...]

To Set the displays so that the external monitor will mirror the current display:

$ xrandr --output HDMI3 --same-as LVDS1 

Check your screen display names (LVDS1 etc..).

xrandr script to put at /usr/local/bin/hotplug_monitor.sh:

#! /usr/bin/bash
export DISPLAY=:0
export XAUTHORITY=/home/YOUR_USER_NAME_GOES_HERE/.Xauthority
function connect(){
  xrandr --output HDMI3 --same-as LVDS1

}
function disconnect(){
  xrandr --output HDMI3 --off
}
xrandr | grep "HDMI3 connected" &> /dev/null && connect || disconnect