[2024-feb-29] Sad news: Eric Layton aka Nocturnal Slacker aka vtel57 passed away on Feb 26th, shortly after hospitalization. He was one of our Wiki's most prominent admins. He will be missed.

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Dual Monitors

Known to work on Slackware 14.1 and XFCE

If you are running XFCE and your secondary monitor isn't working, check and make sure it's enabled in XFCE's SETTINGS:

SETTINGS > SETTING MANAGER > DISPLAY > display name in column on left > USE THIS OUTPUT

Mirror Monitors

By default, XFCE (the WM I use) seems to do this by default.

Extend Desktop To Second Monitor

To extend the desktop to a second monitor (as opposed to mirror the desktop), you need to use xrandr to move the desk top over X number of pixels. Where X = your LEFT monitor's X resolution.

1) Make sure your video card's output is being 'seen' by the system and get the output names:

 xrandr -q 

( Make note of the name of your secondary monitor. )

2) Move the secondary monitor over to the right

 xrandr --output HDMI-0 --pos 1024x0 # to move the VGA screen 1024 pixels to the right. 

EXAMPLE: Here's my machine. DVI-I-2 is my LEFT monitor and HDMI-0 is my RIGHT monitor.

[arfon@darkstar ~]$ xrandr -q
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
DVI-I-0 disconnected (normal left inverted right x axis y axis)
DVI-I-1 disconnected (normal left inverted right x axis y axis)
DVI-I-2 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 336mm
   1920x1080      60.0*+
   1680x1050      60.0  
   1440x900       59.9  
   1280x1024      75.0     60.0  
   1280x960       60.0  
   1280x800       59.8  
   1280x720       60.0  
   1152x864       75.0  
   1024x768       75.0     70.1     60.0  
   800x600        75.0     72.2     60.3     56.2  
   640x480        75.0     72.8     59.9  
HDMI-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 521mm x 293mm
   1920x1080      60.0*+   59.9     60.1     60.0  
   1440x480       60.1  
   1280x720       60.0     59.9  
   1024x768       75.0     70.1     60.0  
   800x600        75.0     60.3  
   720x480        59.9     60.1  
   640x480        75.0     59.9     59.9  
DVI-I-3 disconnected (normal left inverted right x axis y axis)
[arfon@darkstar ~]$ xrandr --output HDMI-0 --pos 1920x0

Cool Switching Scripts

Here's a script I wrote to toggle between extended dual monitors and a single monitor-

#!/bin/bash
vPRIMARYMONITOR="DVI-I-0" # <--- CHANGE THIS.  Find using "xrandr -q"
vLOC="--right" # <--- Change this if you want the second monitor in another position. CHOICES: --above  --below  --left  --right
vEXT=$(xrandr -q | grep " connected" | grep -v $vPRIMARYMONITOR | awk '{print $1}' | head -n 1 )
vOnOff=$(xrandr -q | grep $vEXT | sed 's/primary//g' | awk '{print $3}'| sed 's/[0-9]*x[0-9]*+[0-9]*+[0-9]*/ON/g' )
[ "$vOnOff" != "ON" ] && vOnOff="OFF"
if [ "$vOnOff" = "OFF" ]; then
        /usr/bin/xrandr --output $vEXT --auto $vLOC $vPRIMARYMONITOR
        else
        /usr/bin/xrandr --output $vEXT --off
        fi

Script to toggle a mirrored monitor-

#!/bin/bash
vPRIMARYMONITOR="DVI-I-0" # <--- CHANGE THIS.  Find using "xrandr -q"
vEXT=$(xrandr -q | grep " connected" | grep -v $vPRIMARYMONITOR | awk '{print $1}' | head -n 1 )
vOnOff=$(xrandr -q | grep $vEXT | sed 's/primary//g' | awk '{print $3}'| sed 's/[0-9]*x[0-9]*+[0-9]*+[0-9]*/ON/g' )
[ "$vOnOff" != "ON" ] && vOnOff="OFF"
if [ "$vOnOff" = "OFF" ]; then
	/usr/bin/xrandr --output $vEXT --auto
	else
	/usr/bin/xrandr --output $vEXT --off
	fi

Sources

 howtos:window_managers:dual_monitors ()