Bug 1213113

I reckon this is a mutter issue.

mutter seems to have a "grab" on Super, and it won't pass events down to Wayland for those, meaning that Xwayland will not be notified of Super key press events and therefore won't apply the modifier mask accordingly.

This is in mutter/core/events.c:

https://git.gnome.org/browse/mutter/tree/src/core/events.c#n310  

155 static gboolean
156 meta_display_handle_event (MetaDisplay        *display,
157                            const ClutterEvent *event)
158 {
[...]
302   /* If the compositor has a grab, don't pass that through to Wayland */
303   if (display->event_route == META_EVENT_ROUTE_COMPOSITOR_GRAB)
304     bypass_wayland = TRUE;
305 
306   /* If a Wayland client has a grab, don't pass that through to Clutter */
307   if (display->event_route == META_EVENT_ROUTE_WAYLAND_POPUP)
308     bypass_clutter = TRUE;
309 
310 #ifdef HAVE_WAYLAND
311   if (compositor /* && !bypass_wayland */)
312     {
313       if (meta_wayland_compositor_handle_event (compositor, event))
314         bypass_clutter = TRUE;
315     }
316 #endif

When pressing the "Super" key, bypass_wayland is TRUE and meta_wayland_compositor_handle_event() is not called.

As a proof of concept, for debugging purpose, removing that "!bypass_wayland" fixes the issue, Xwayland correctly report the modifier mask in the button press/release events - Obviously, this is not the correct fix, but it shows the issue is not in control-center nor in Xwayland.

Moving to mutter for further investigation.

Confirming, this is real and messing with the workstation setup. I'm currently on gnome-3.18, did anything with this bug improve perhaps as a side-effect in gnome-3.20 or later?

In gnome 3.20 (gnome-shell-3.20.2-1.fc24.x86_64) this seems to be improved. Behaviour is still slightly erratic: some bindings are successfully created in the "Keyboard" dialog, others aren't. I think that if there is an existing binding, it gets executed before "Keyboard" sees it. I would expect instead to see a notification that this binding is already bound. Nevertheless, situation is greatly improved, I'd say that this is 80% fixed.

Fedora 22 changed to end-of-life (EOL) status on 2016-07-19. Fedora 22 is
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This is still a problem in Fedora 24. I have emacs bindings to super-e and super-q and emacs is just seeing e and q.

It looks like Super_R is getting through, but not Super_L. I would guess bypass_wayland isn't being set not because of a grab, but because of something inside the call to meta_keybindings_process_event, maybe process_key_event -> process_overlay_key, since Super_L is the overlay key.

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Seems even better in F26... I think it's OK to let this go EOL.

... or even to just close it.