Media keys (ctrl-alt-t, brightness, play/pause) don't work randomly after logging

[Will Cooke]

I've installed 15.10 and I can't open a terminal using ctrl-alt-t or use any other media keys. All system shorcuts as well don't work.

Note that this started at least in 14.10.

Restarting Unity "fixes" it (or logging out/logging back), so it seems a race between Unity and settings daemon at startup.

[Will Cooke (willcooke)]

This looks like a race condition. It works now?!

[Didier Roche (didrocks)]

I'm getting it for a couple of releases. It was one on 10 login before. It seems recently, it's one every 4 of them, so quite high in term of frequency.

monitoring and pressing a media key gives:
signal time=1443171424.483295 sender=:1.28 -> destination=(null destination) serial=7116 path=/org/gnome/Shell; interface=org.gnome.Shell; member=AcceleratorActivated
   uint32 33
   uint32 0
   uint32 9782134

So, the signal is sent.

I checked, and I have u-s-d running.

[Lars Karlitski (larsu)]

Problem figured out by Trevinho and didrocks on irc: unity only emits AcceleratorActivated() for the first id returned by GrabAccelerator() and doesn't watch the unique name of the grabbing process. Thus, when something other than unity-settings-daemon grabs the key before it, or u-s-d crashes, those keys it grabbed at the very beginning can never be regrabbed.

After a couple of rounds of testing and some code review, I can't make unity-settings-daemon subscribe to the same accelerator twice and thus getting into that situation itself. Feel free to reassign it to u-s-d once unity is fixed but this problem still persists.