cursor: process layer subsurfaces in cursor_button_press() and fix a layer-surface bug in get_cursor_context()

[johanmalm]

...to give keyboard focus to layer-shell clients if exclusive or on-demand interactivity is set, so that menu popups can be navigated with the keyboard. This still only works if the client is in top (or overlay) layers. Support for bottom and background to be done as a separate patch set.

Revert 06b19f0 to process layer-shell subsurfaces in cursor_button_press(), but only when their parent layer-shell surface has keyboard interactivity.

In get_cursor_context() process layer-surfaces and layer-subsurfaces from surfaces rather than nodes.

Background:

Commit 06b19f0 (issue #1131) disabled processing of layer-shell subsurfaces in cursor_button_press() because when pressing a task in Waybar (Gtk panel using layer-shell subsurfaces) the foreign-toplevel minimize-raise action did not work correctly as the action logic relied on the recipient window being activated and by clicking on the panel, the panel itself was both surface-focusd and activated (and thus the window de-activated).

The un-intended consequence was that by not responding to layer-subsurface cursor buttons presses, layer-shell clients (such as panels) were not given keyboard focus if they indeed wanted it by setting exclusive or on-demand keyboard interactivity.

The good news is that that following @jlindgren90's refactoring (various) the only place where we call view_set_actived() is in focus_change_notify() in seat.c and we now only do it for views (bb8f0bc).

Another side-effect (positive) of 06b19f0 was that a Waybar dnd bug was fixed (pointer-serial-number validation failure).

Have tested with sfwbar, waybar and tint (test-panel) the following results:

• Minimize-raise works even when on-demand keyboard interactivity is set
• Keyboard interactivity is given popup-menus (sfwbar and tint) when the panels are in the top layer (support for bottom will be as a separate patch set)
• Waybar dnd still works (even when hard-coding keyboard-interactivity)

References:

• bb8f0bc

• labwc/src/seat.c

  Lines 481 to 483 in 40ce95a

  	if (surface && !view) {
  	return;
  	}

• labwc/src/dnd.c

  Line 24 in 40ce95a

  wlr_log(WLR_ERROR, "wrong source for drag request");

• https://github.com/johanmalm/tint

Fixes: #1572

[stefonarch]

Tested with lxqt-panel (after changing KeyboardInteractivityNone to KeyboardInteractivityOnDemand) and pcmanfm-qt --desktop (this worked with the patch) - looks working fine.

Thanks!

[Tamaranch]

Looks like it would also fix #1554 :)

[Tamaranch]

I can also confirm that it does allow you to navigate xfce4-panel menus via the keyboard (internal plugins in the panel surface, or external plugins on their own layer-shell surface in overlay), and that it also solves that old problem of not being able to close the menu via the Escape key (we must have talked about this somewhere, but I can't remember where :)).

[johanmalm]

Thanks both for testing.
Have refactored a bit following conversation with @Consolatis
Ready for final review + merge.

[Consolatis]

Had a quick test nested and it improves things quite a bit, thanks for your work on this :)