GTK3 breaking key grab rules?

[Chris Dekter <cdekter gmail com>]

Hi list,

I am the developer of an application named AutoKey. One of the features 
of AutoKey is allowing the user to create hotkeys. The hotkeys are 
grabbed using the xlib window.grab_key() function. In all other desktop 
environments to date, grabbing a hotkey in the root window using this 
method causes that hotkey to no longer be received by any other 
application, which is exactly what I want. However, in Gnome Shell, with 
GTK3 applications, for some reason this breaks down. Hotkeys grabbed in 
the root window are still received by other GTK3 applications, unless I 
specifically grab the hotkey in every window in the tree. KDE 
applications running under Gnome Shell are not affected by this issue.

I have tried implementing various nasty workarounds but they are slow 
and unreliable. Ideally I'd like to understand what GTK3 is doing that 
is causing this behaviour and see if there is another way around it.

Thanks,
Chris Dekter