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92 lines
3.1 KiB
Markdown
92 lines
3.1 KiB
Markdown
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---
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title: Dual-headed X11
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layout: default
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created: 2008-08-11 18:10:56 +0200
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updated: 2009-07-23 12:44:36 +0200
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toc: false
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tags:
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- know-how
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- software
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- linux
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- display
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- x11
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---
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per user
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========
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The native screen-size detection doesn't work for dual-head installations. To let X11 handle both screens as one large
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display, find the section `Screen` in the `/etc/X11/xorg.conf` and add the following lines:
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~~~
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SubSection "Display"
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Virtual 2560 1024
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EndSubSection
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~~~
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This is for two 1280x1024 displays side-by-side (1280+1280 = 2560). Now you can use `xrandr` to set displays.
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xrandr -q
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Shows all available displays. Usually it will show the devices `VGA-0` and `LVDS`. To change the output of the external
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display to be left of the internal LCD panel, use something like
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xrandr --output VGA-0 --left-of LVDS
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You might also have to use *System* → *Preferences* → *Screen Resolution* to configure the location of the displays.
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Fix screen order
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----------------
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Under *Intrepid*, it often happens to me that my screenorder is wrong after login. This is shown by a mirrored output on
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the left display, but the system thinks that there's a left workspace. On rare occassions, I even have the wrong order
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(i.e. if I move the mouse to the right on the right workspace, it appears on the left display's workspace.) This is
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quickly fixed by switching the order around:
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{% highlight bash %}
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#!/bin/sh
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echo Switching position of displays
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xrandr --output VGA-0 --right-of LVDS
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echo Switching off ext. display
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xrandr --output VGA-0 --off
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echo Switching back to normal
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xrandr --output VGA-0 --mode 1280x1024 --rate 75 --left-of LVDS
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{% endhighlight %}
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After calling the script, my displays are showing the correct workspaces.
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system-wide
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===========
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To configure dual-head system-wide (for Desktop computers), there is a great manual at [UbuntuForums](http://ph.ubuntuforums.com/showthread.php?t=826717).
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1. Use `xrandr -q` to get the output device's names (for me it was `VGA-0` and `DVI-0`)
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1. open the `/etc/X11/xorg.conf` in your favorite editor
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1. find the section `Device` and add 2 lines so that it looks like this:
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Section "Device"
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Identifier "Configured Video Device"
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Option "monitor-VGA-0" "right"
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Option "monitor-DVI-0" "left"
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EndSection
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1. The device names have to be prefixed with `monitor-`. The names after that are for you to choose.
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1. find the `Monitor` section and change the identifier to one of the names. (e.g. `right`)
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1. add another `Monitor` section below and change the identifier to the other name. (`left`) Also add the
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line `Option "LeftOf" "right"` in between.
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1. now the both monitor sections should look like this:
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Section "Monitor"
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Identifier "right"
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EndSection
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Section "Monitor"
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Identifier "left"
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Option "LeftOf" "right"
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EndSection
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1. find the `Screen` section and add the following line to define the default display.
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Monitor "right"
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1. add a `SubSection "Display"` and the `Virtual` line as with the per-user configuration
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1. save the file and restart X
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