experimental: use wlr_xwayland_surface_offer_focus()

Offer focus by sending WM_TAKE_FOCUS to a client window supporting it.
The client may accept or ignore the offer. If it accepts, the surface will
emit a focus_in signal notifying the compositor that it has received focus.
The compositor should then call wlr_xwayland_surface_activate(surface, true).

This is a more compatible method of giving focus to windows using the
Globally Active input model (see wlr_xwayland_icccm_input_model()) than
calling wlr_xwayland_surface_activate() unconditionally, since there is no
reliable way to know in advance whether these windows want to be focused.

include/view.h

@@ -94,6 +94,7 @@ struct view_impl {
 	struct view_size_hints (*get_size_hints)(struct view *self);
 	/* if not implemented, VIEW_WANTS_FOCUS_ALWAYS is assumed */
 	enum view_wants_focus (*wants_focus)(struct view *self);
+	void (*offer_focus)(struct view *self);
 };
 
 struct view {
@@ -320,6 +321,8 @@ view_is_focusable(struct view *view) {
 	return view_is_focusable_from(view, NULL);
 }
 
+void view_offer_focus(struct view *view);
+
 void view_toggle_keybinds(struct view *view);
 
 void view_set_activated(struct view *view, bool activated);

include/xwayland.h

@@ -34,6 +34,7 @@ struct xwayland_view {
 	struct wl_listener set_decorations;
 	struct wl_listener set_override_redirect;
 	struct wl_listener set_strut_partial;
+	struct wl_listener focus_in;
 
 	/* Not (yet) implemented */
 /*	struct wl_listener set_role; */

src/desktop.c

@@ -67,17 +67,20 @@ desktop_focus_view(struct view *view, bool raise)
 		workspaces_switch_to(view->workspace, /*update_focus*/ false);
 	}
 
-	/*
+	switch (view_wants_focus(view)) {
-	 * Give input focus, even if the view claims not to want it (see
+	case VIEW_WANTS_FOCUS_ALWAYS:
-	 * view->impl->wants_focus). This is a workaround for so-called
+		; /* works around "a label can only be part of a statement" */
-	 * "globally active" X11 views (MATLAB known to be one such)
-	 * that expect to be able to control focus themselves, but can't
-	 * under labwc since it's disallowed at the wlroots level.
-	 */
 		struct seat *seat = &view->server->seat;
 		if (view->surface != seat->seat->keyboard_state.focused_surface) {
 			seat_focus_surface(seat, view->surface);
 		}
+		break;
+	case VIEW_WANTS_FOCUS_OFFER:
+		view_offer_focus(view);
+		break;
+	case VIEW_WANTS_FOCUS_NEVER:
+		break;
+	}
 
 	if (raise) {
 		view_move_to_front(view);

src/view.c

@@ -178,6 +178,15 @@ view_is_focusable_from(struct view *view, struct wlr_surface *prev)
 			&& prev && view_is_related(view, prev)));
 }
 
+void
+view_offer_focus(struct view *view)
+{
+	assert(view);
+	if (view->impl->offer_focus) {
+		view->impl->offer_focus(view);
+	}
+}
+
 /**
  * All view_apply_xxx_geometry() functions must *not* modify
  * any state besides repositioning or resizing the view.

src/xwayland.c

@@ -100,6 +100,12 @@ xwayland_view_wants_focus(struct view *view)
 	return VIEW_WANTS_FOCUS_NEVER;
 }
 
+static void
+xwayland_view_offer_focus(struct view *view)
+{
+	wlr_xwayland_surface_offer_focus(xwayland_surface_from_view(view));
+}
+
 static struct wlr_xwayland_surface *
 top_parent_of(struct view *view)
 {
@@ -280,6 +286,7 @@ handle_destroy(struct wl_listener *listener, void *data)
 	wl_list_remove(&xwayland_view->set_decorations.link);
 	wl_list_remove(&xwayland_view->set_override_redirect.link);
 	wl_list_remove(&xwayland_view->set_strut_partial.link);
+	wl_list_remove(&xwayland_view->focus_in.link);
 
 	view_destroy(view);
 }
@@ -467,6 +474,18 @@ handle_set_strut_partial(struct wl_listener *listener, void *data)
 	}
 }
 
+static void
+handle_focus_in(struct wl_listener *listener, void *data)
+{
+	struct xwayland_view *xwayland_view =
+		wl_container_of(listener, xwayland_view, focus_in);
+	struct view *view = &xwayland_view->base;
+	struct seat *seat = &view->server->seat;
+	if (view->surface != seat->seat->keyboard_state.focused_surface) {
+		seat_focus_surface(seat, view->surface);
+	}
+}
+
 static void
 set_initial_position(struct view *view,
 		struct wlr_xwayland_surface *xwayland_surface)
@@ -790,6 +809,7 @@ static const struct view_impl xwayland_view_impl = {
 	.is_related = xwayland_view_is_related,
 	.get_size_hints = xwayland_view_get_size_hints,
 	.wants_focus = xwayland_view_wants_focus,
+	.offer_focus = xwayland_view_offer_focus,
 };
 
 void
@@ -834,6 +854,7 @@ xwayland_view_create(struct server *server,
 	CONNECT_SIGNAL(xsurface, xwayland_view, set_decorations);
 	CONNECT_SIGNAL(xsurface, xwayland_view, set_override_redirect);
 	CONNECT_SIGNAL(xsurface, xwayland_view, set_strut_partial);
+	CONNECT_SIGNAL(xsurface, xwayland_view, focus_in);
 
 	wl_list_insert(&view->server->views, &view->link);