[ubuntu][xrandr] Autodetect Display

cant get to work, use autorandr instead
https://github.com/phillipberndt/autorandr
config file on ~/.config/autorandr/ just in case some error(like what happened to me), just edit some parameter on those files that make errors,

taken from https://unix.stackexchange.com/a/11891 with fix and personal customization

I'm using this simple (homemade) script that keeps polling RandR and switches between LVDS1 and VGA1 when VGA gets connected/disconnected. (For HDMI outputs, in the following script file, change all the VGA1 to HDMI1)

It's a dirty solution, yet it's working just fine.

It's customized for my setup: you'll most likely need to change RandR output names (LVDS-1 and VGA-1) and unlike me you'll probably be fine with your RandR default mode for VGA.

Add Missing Resolution

Check display name

• type xrandr in console

Check parameter to -newmode

• type cvt [res diagonal] [res vertical]
  • ie: cvt 1360 768
• you will see

  # 1360x768 59.80 Hz (CVT) hsync: 47.72 kHz; pclk: 84.75 MHz
  Modeline "1360x768_60.00"   84.75  1360 1432 1568 1776  768 771 781 798 -hsync +vsync

• add string after Modeline to xrander --newmode

  xrandr --newmode "1360x768-60.00"  84.75  1360 1432 1568 1776  768 771 781 798 $

• then xrandr --addmode

  xrandr --addmode VGA-1 1360x768-60.00

  Auto detect display connected and auto change xrandr mode

1. Make file into profile.d

   sudo nano /etc/profile.d/xrandr_external_monitor.sh

   fill with below code, this code is customized, you can change xrandr --output whatever you need

   #!/bin/bash
   
   # setting up new mode for my VGA
   xrandr --newmode "1360x768-60.00"  84.75  1360 1432 1568 1776  768 771 781 798 $
   
   xrandr --addmode VGA-1 1360x768-60.00
   
   # default monitor is LVDS-1
   MONITOR=LVDS-1
   
   # functions to switch from LVDS1 to VGA and vice versa
   function ActivateVGA {
       echo "Switching to VGA-1"
       xrandr --output VGA-1 --mode 1360x768-60.00 --dpi 160 --output LVDS-1 --off
       MONITOR=VGA-1
   }
   function DeactivateVGA {
       echo "Switching to LVDS1"
       xrandr --output VGA-1 --off --output LVDS-1 --auto
       MONITOR=LVDS-1
   }
   
   # functions to check if VGA is connected and in use
   function VGAActive {
       [ $MONITOR = "VGA-1" ]
   }
   function VGAConnected {
       ! xrandr | grep "^VGA-1" | grep disconnected
   }
   
   # actual script
   while true
   do
       if ! VGAActive && VGAConnected
       then
        ActivateVGA
       elif VGAActive && ! VGAConnected
       then
          DeactivateVGA
       else
           xrandr --auto
       fi
   
       sleep 1s
   done
   

2. Make the .sh file executable by typing the following command in the terminal

   chmod +x /etc/profile.d/xrandr_external_monitor.sh

3. reboot to see the effect