How do I find out what program 'owns' a hotkey?

Question

I'm running XFCE 4.12 on top of Gentoo with a 4.2.0 kernel. My PlayPause button on my keyboard used to work as a global hotkey for VLC. Now VLC won't even recognize the key. It does see "Alt + Media Play Pause" but not the key alone.

Is there a way to see if and what program might be capturing that key?

When I run xdotool key "XF86LogGrabInfo" the tail /var/log/Xorg.0.log file reads

[ 10138.690] (II) Printing all currently active device grabs:
[ 10138.690] (II) End list of active device grabs

Answer 1

To find out which app/program grabbed your key use the debug keysym XF86LogGrabInfo. Use xdotool to press keys + XF86LogGrabInfo at the same time e.g. in a terminal run

KEY=XF86AudioPlay
xdotool keydown ${KEY}; xdotool key XF86LogGrabInfo; xdotool keyup ${KEY} 

Then check for output with tail /var/log/Xorg.0.log
Note that with gnome 3/gdm and systemd this is no longer logged to Xorg.0.log (it's instead logged to the journal). In that case you could run

journalctl -f

and then in another terminal run the xdotool commands. Switch to the first terminal and you'll see something like

/usr/lib/gdm/gdm-x-session[629]: Active grab 0x40c0a58e (xi2) on device 'Virtual core keyboard' (3):
/usr/lib/gdm/gdm-x-session[629]: client pid 708 /usr/bin/gnome-shell
/usr/lib/gdm/gdm-x-session[629]: at 32595124 (from passive grab) (device frozen, state 6)
/usr/lib/gdm/gdm-x-session[629]: xi2 event mask for device 3: 0xc000
/usr/lib/gdm/gdm-x-session[629]: passive grab type 2, detail 0xac, activating key 172

In the above example the program (the client) that grabbed the key is gnome-shell.