[Discuss] NVidia 2 screen problem

[tmetro+blu at gmail.com (Tom Metro)]

David Kramer wrote:
> - No matter what I do, some apps refuse to appear on the TV.  No matter
> how I launch them or what I set $DISPLAY to, they always come up on my
> monitor instead of my TV.

Probably some tiny fraction of applications get tested in an environment
where DISPLAY != :0. In fact they probably get more testing with the
display pointed at a remote X server than at an alternate display in the
same machine. So you have something like:
DISPLAY=:1
? You might try variations that include the host:
DISPLAY=localhost:1
DISPLAY=<your LAN IP>:1

(You'll likely have to change permission settings in X to allow remote
connections when using your LAN IP.)

You should definitely file bugs against any applications that fail to
handle this. It should be handled by fairly low-level X libraries that
should be used by all of your X applications.

Another option to experiment with might be to use a VM. It seems like
useless overhead, but to all the applications running within the VM host
they'll think they are talking to the primary display. Now only the VM
host needs to be well behaved in respecting the DISPLAY specification.
(I've read reports that MythTV back-end will behave OK in a VM. The
front-end might as well.)


> A few days ago, I experienced a problem where everything was working as
> before, but no windows on the TV could get keyboard input.  I can work
> them with the mouse, but not the keyboard.

I've seen that happen with simpler setups. Sometimes restarting the
window manager will resolve it. But that can be tricky to do when the
keyboard isn't working.


> ...I set it up the way it used to be, I still had the
> lack-of-keyboard problem...

Oh, it persists even after a reboot? If, as you say, your hardware is
working, then obviously a software update or config change is to blame.
Check your logs to see what packages were updated correlating with the
breakage.


> In desperation, I changed my nVidia settings to use TwinView.  I could
> then move windows between screens which was nice, but:
> - Switching desktops switched both screens, so if I was watching
> mythfrontend on the TV and wanted to switch to another desktop on my
> monitor, the TV would switch away from mythfrontend too.

Cinnamon, under Cinnamon Settings->Workspaces, has an option to "only
use workspaces on primary monitor." The same feature may exist on other
desktops (if you can find it), as most features in Cinnamon are borrowed
or duplicated from other desktops.

As you mention TwinView I assume you're using the proprietary nVidia
drivers. You should give the open source nouveau driver a spin. I
switched to it several months back when I started getting warnings from
Cinnamon that hardware acceleration was no longer working and my CPU
usage was being driven up. Not sure if this was due to a change in the
proprietary driver or in Cinnamon (I'm more likely to suspect Cinnamon,
which gets reved more often), but switching to nouveau cured it. nouveau
 seems to spew warnings into the kernel log regularly, and I experienced
some stability issues initially, but those seem to have settled down. It
seems to handle my multi-monitor setup well.


> I'm willing to go in either direction...

It seems like even before you had this keyboard problem, you had issues
with this multi-monitor setup, and even if you get them resolved, it is
likely to be a fragile arrangement. What happens the next time you
update Kubuntu? You could be weeks getting things reconfigured to get
this unusual setup working again.

I second the recommendation of another poster and suggest you look at
moving the MythTV front-end to dedicated hardware. Have an old laptop?
If not, you can probably source adequate hardware for under $200. That
way you can treat it like an appliance and not worry about it
interacting with your general desktop.

 -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/