xRandr and dual screen

(~2 minutes)

As always when you have to study an exam, you notice something on your computer that doesn’t work … Today was the easy way to connect an external display and use it to … hum … work.

As I don’t use fancy desktop environment, no gui tools are available. That’s not a problem, you just have to do it the easy way: Some obscure key bindings that will launch a script that will do what you wanted.

The program used for display “manipulations” is xrandr. Very useful, simple, does what it claims to do … and command line ! Perfect, let’s do our little script :

#!/bin/bash
RESOLUTION="800x600"
INTERNAL="LVDS1"
EXTERNAL="VGA1"
touch /tmp/xrandr
loop=`cat /tmp/xrandr`
case "$loop" in
	vga_right)
		xrandr --output $INTERNAL --auto --output $EXTERNAL --auto --left-of $INTERNAL
		echo "vga_left" > /tmp/xrandr
		;;
	vga_left)
		xrandr --output $INTERNAL --mode $RESOLUTION --output $EXTERNAL --mode $RESOLUTION --same-as $INTERNAL
		echo "vga_double" > /tmp/xrandr
		;;
	vga_double)
		xrandr --output $INTERNAL --auto --output $EXTERNAL --off
		echo "vga_off" > /tmp/xrandr
		;;
	*)
		xrandr --output $INTERNAL --auto --output $EXTERNAL --auto --right-of $INTERNAL
		echo "vga_right" > /tmp/xrandr
		;;
esac

To be able to use it, just modify the internal and external display name. You can find them just by typing:

$ xrandx -q
</pre>
The output should tell you the names: 
<pre>
Screen 0: minimum 320 x 200, current 2880 x 1200, maximum 8192 x 8192
VGA1 connected 1600x1200+1280+0 (normal left inverted right x axis y axis) 408mm x 306mm
   1600x1200      60.0*+
   1280x1024      75.0     60.0  
[...]
LVDS1 connected 1280x800+0+0 (normal left inverted right x axis y axis) 286mm x 179mm
   1280x800       59.9*+
   1024x768       85.0     75.0     70.1     60.0  
[...]
TV1 disconnected (normal left inverted right x axis y axis)