KDE plasma second monitor issues after latest update

[Duncan]

CS DBA posted on Mon, 04 Jan 2016 12:38:06 -0700 as excerpted:

> Sorry if this is a duplicate - email issues...

It is, but... understood.

> I applied the latest updates today, second monitor capability is still
> broken;
> 
> I plug in the HDMI cable, go to system settings --> Display and it only
> show the laptop screen.
> 
> The Cinnamon desktop continues to work flawlessly per auto-adding the
> second monitor as soon as I plug the HDMI cable in, thus seemingly
> confirming it's a KDE issue and not a Kernel issue.  I do prefer KDE
> Plasma over Cinnamon, but I need the second monitor to work. Anyone have
> any thoughts on debugging this?


Still not on plasma5 myself, tho last I tried I got close enough to see 
that it was working on my triple monitor setup just fine... at least for 
initial setup.  It was another bug that had me revert to kde4...

But, I don't know why I didn't think of and post this before... but 
there's a generic X commandline XRandR client called... xrandr.  After 
installing it if necessary, try reading its manpage, and then running it 
from a terminal window (konsole or the like).

Your lspci output says Intel graphics, which is well supported with open 
drivers and indeed, I don't believe there's proprietary drivers even 
available, so it shouldn't be a problem there.

Just running xrandr without any options should give you a listing of the 
outputs available and active or not, possible resolutions, etc.  From the 
manpage you can figure out how to issue commands to try to activate 
inactive outputs, etc.

Of course the plasma/kde utilities _should_ allow you do do the same 
thing in a GUI, but from my own experience, they've been bugged out and 
broken in some way or another more of the time than they actually work.  
If you can figure out how to run the cinnamon display configurator in kde/
plasma, you /may/ be able to use it to activate the second monitor even 
in plasma, but I've not run cinnamon so I don't know for sure and can't 
help you with it.

But the xrandr commandline option is very likely to work if it's possible 
to do what you need with RandR at all.  I know it has worked very well 
for me when kde's tools don't.  It's just that you have to use the 
command line to do it then, and using the commandline to configure what 
is by definition a GUI setting, just seems... unnatural... and shouldn't 
be necessary.  But unfortunately, I've had to keep it around, because as 
I said, kde's tools seem to be broken more than not.


The one good thing about xrandr is that if you're comfortable doing shell 
scripting, once you figure out the commands you need to get the setup you 
want, it's quite simple to put them in a script, which you can call 
whenever you need. =:^)


If xrandr isn't seeing the second output/monitor either, then it's likely 
a bug deeper than RandR itself, and you'd need other tools.  But since 
cinnamon works, were I to bet, xrandr should be able to handle it too, 
provided of course that you can figure out how to work xrandr at the 
command line, something that was easy for me, but won't necessarily be so 
easy for some.

-- 
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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