Comment 99 for bug 1308105

Looking at Sean's comment of 2015-02-19, it appears that a functional patch is still being sought. I am experiencing the problem of the display not coming back when it is reconnected. I'm posting this in hopes that it assists the maintainers of the code in resolving the issue. With the 4.12 branch from git, I was able to reproduce this bug with just a regular desktop (non HDMI) by disconnecting and reconnecting the monitor. When the monitor was reconnected, the screen does not resume.

In the xfce_displays_helper_screen_on_event function in the top section it has the condition of the disconnection of the monitor. In that section it is calling a forced disable of the crtc via

  crtc->mode = None;
  xfce_displays_helper_disable_crtc (helper, crtc->id);

However, in the else condition below where it is adding in new outputs, the crtc is still in a disabled status when this gets executed after the cable has been reattached. (mode = None, width=0, etc)

I think that the proper solution is to get the crtc re-enabled/refreshed upon reconnection and I'm hoping that those that actually know this code would know how to do this (I tried a couple of options across various functions but they did not work).

The interim "hack" solution that seems to work for me is to comment out the code that is disabling the crtc. This doesn't seem to spawn additional displays but may other regression problems. And since it is a true hack rather than a correct solution, I'm not attaching it as a patch.

Hope this helps, let me know if testing is needed or if you can point me to the proper method of getting the crtc information refreshed.