Bug 1056251

+++ This bug was initially created as a clone of Bug #840913 +++

Description of problem:
In System Settings - Displays I'm able to active 3 displays (1 laptop built-in, 2 external), but my graphic card/drive supports only 2 displays, so it causes X server freeze

Version-Release number of selected component (if applicable):
kscreen-1.0.1-6.el7.x86_64
kernel-3.3.0-0.17.el7.x86_64
xorg-x11-drv-nouveau-0.0.16-36.20120306gitf5d1cd2.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Have 2 external displays connected + 1 laptop built-in
2. In System Settings - Displays click to the inactive one and activate it
3. Apply
  
Actual results:
There are no rendering artifacts in KDE nor crash either.

But System Settings KScreen behavior is also buggy. It shows second external monitor as enabled and doesn't warn user about unsupported by HW setup.

Expected results:
Any message that I'm not able to do that, it's not supported or something like that; no freeze

--- Additional comment from Martin Holec on 2014-01-16 12:22:24 EST ---

I confirm there is no crash on latest RHEL7.

I have HD3000 GPU, T420s laptop display + external monitor setup. When I connect second monitor and enable it in control-center I got following error:

"Failed to apply configuration: %s
Timeout was reached"

You can see this on the screenshot.

control-center shows second monitor miniature as enabled, but monitor stays actually off.

There is an artifact in Gnome Shell: Left half of left screen is rendered in the center of middle screen. Going into activities hides artifact temporally, going back shows it again. This seems to be like compositing issue.

No error in Xorg.log.0, dmesg or journalctl.

--- Additional comment from Martin Holec on 2014-01-16 12:34:13 EST ---

There are no rendering artifacts in KDE nor crash either.

But System Settings Display behavior is also buggy. It shows second external monitor as enabled and doesn't warn user about unsupported by HW setup.

I see 2 problems here:

1) Integration between Xorg and both Gnome/KDE desktops for unsupported screen configurations.
2) gnome-shell or DRM (kernel) rendering/compositing issue.**

**TODO: File separate bug, after we decided which component is buggy.

--- Additional comment from Dan Vrátil on 2014-01-17 08:56:21 EST ---

(In reply to Martin Holec from comment #7)
> 1) Integration between Xorg and both Gnome/KDE desktops for unsupported
> screen configurations.

Can't speak for the kernel/driver part, but on KDE/Gnome side we can detect maximum number of configured screens by counting available CRTCs, which is exposed via XRandR extension.

Could you file a bug for KScreen if you think we should handle the situation there too?