How to setup dual monitor in kde?

Duncan 1i5t5.duncan at
Fri May 25 03:40:53 BST 2012

Marcelo Magno T. Sales posted on Thu, 24 May 2012 08:53:15 -0300 as

> Hello,
> I would like to extend my desktop to my second monitor. KDE defaults to
> clone the image of the main monitor on the secondary monitor.
> I can setup the desktop the way I want, with the secondary monitor above
> the primary one, using KDE System Settings. However, this setup does not
> survive a reboot and every time I turn on the computer, I have to setup
> the desktop again.
> Is there a way to make the dual monitors configuration to stick using
> KDE's GUI tools or do I need to create a xorg.conf file and edit it
> manually?
> I'm running Kubuntu 12.04 (Precise Pangolin).

I was debating where in-thread to post, but decided to punt and start a 
new top-level sub-thread...

Most direct answer:  Try starting krandrtray, and setting it to start 
with kde.  AFAIK, that's the bit that actually applies the default 
display profile on kde startup, so if it's not started with kde, you 
won't get the display profile applied.

(Depending on what you have the kde session manager set to do, it may 
simply restart krandrtray if it was running when kde was last shutdown, 
or you may have to add it to the memorized session that's restarted, or 
you can set krandrtray in the autostart configuration.  I have mine there 
but have it disabled as I don't need it, normally.)

Meanwhile, keep in mind that it was only with kde 4.4 or 4.5 that kde 
display settings actually started working.  They had never worked at all, 
since they were introduced back in the kde3 era, for many users, and at 
one point in IIRC kde 4.3, just opening the applet (via either kcontrol 
or krandrtray) would seriously screw up the display, just opening it, not 
even changing anything or hitting apply!  You had to really be careful 
browsing kcontrol (aka kde settings) not to hit that applet, during that 

Even now, kde's display setting ability is limited to a small subset of 
xrandr.  Setting a larger desktop than display, with configurable 
panning, isn't properly supported, for instance, let alone keystoning, 

As a result, many users had to use other display setup methods, xorg.conf 
(now a file in xorg.conf.d) as I do for my X startup config, xrandr 
scripts as I use to handle resolution switching while keeping the larger 
desktop and enabling panning, etc.  Since they already had that setup and 
working, many people prefer to continue using those solutions to the 
rather limited solution kde offers, even if kde's solution isn't as 
horribly broken as it used to be, especially because once you've seen the 
flexibility of the other solutions, kde's solution remains quite limited 
in comparison.

Meanwhile, addressing the poster (bjorn.ballard) who asked (essentially) 
about the possibility of saving both a laptop-only and a laptop-plus-
external profile, while that has been discussed and multiple display 
profile support is planned for the future, AFAIK, it's not available in 
current kde.  There's currently only a single profile stored, and storing 
a second one erases the first.

So for displays that come and go, if you're using the internal when you 
use the external too, you could try setting it up in xorg.conf.d, which 
if it's missing the one, will just setup the one it has, and it'll still 
work with both if X is started with both.  (That should also work with 
multiple external displays, BTW, as long as X can tell them apart.  It 
will just configure the ones it sees when it starts, and ignore the 

Alternatively (as nowardev suggested), setup some xrandr scripts and 
simply call the one you want to setup the config you want.  That should 
work for hotplugged monitors too, while the xorg.conf option only works 
(for now, they're working on it...) when you start X.

What I'd do (umm, actually have done...) is setup xorg.conf so it gets it 
right for what I have plugged in when it starts, with xrandr scripts that 
I can invoke if I want to change the setup while X is running.

Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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