seat: use focus_change event to update focused/active view

- Connect to wlr_seat_keyboard_state's focus_change event.
- Add view_from_wlr_surface(), which does what the name says.
- Use focus_change event along with view_from_wlr_surface() to update
  server->focused_view and set SSD states via view_set_activated().
- Eliminate desktop_focused_view() since server->focused_view should be
  reliably up-to-date now.
- Eliminate view_focus/defocus() since we can now just call
  seat_focus_surface() directly.

include/labwc.h

@@ -167,6 +167,7 @@ struct seat {
 	struct wl_client *active_client_while_inhibited;
 	struct wl_list inputs;
 	struct wl_listener new_input;
+	struct wl_listener focus_change;
 
 	struct wl_listener cursor_motion;
 	struct wl_listener cursor_motion_absolute;
@@ -247,11 +248,8 @@ struct server {
 
 	/* SSD state */
 	/*
-	 * Currently focused view (cached value). This pointer is used
-	 * primarily to track which view is being drawn with "active"
-	 * SSD coloring. We consider it a bug if this gets out of sync
-	 * with the actual keyboard focus (according to wlroots). See
-	 * also desktop_focused_view().
+	 * Currently focused view. Updated with each "focus change"
+	 * event. This view is drawn with "active" SSD coloring.
 	 */
 	struct view *focused_view;
 	struct ssd_hover_state *ssd_hover_state;
@@ -395,14 +393,6 @@ enum lab_cycle_dir {
  */
 struct view *desktop_cycle_view(struct server *server, struct view *start_view,
 	enum lab_cycle_dir dir);
-/**
- * desktop_focused_view - return the view that is currently focused
- * (determined on-the-fly from the wlroots keyboard focus). The return
- * value should ideally match server->focused_view (we consider it a
- * bug otherwise) but is guaranteed to be up-to-date even if
- * server->focused_view gets out of sync.
- */
-struct view *desktop_focused_view(struct server *server);
 void desktop_focus_topmost_mapped_view(struct server *server);
 
 void keyboard_cancel_keybind_repeat(struct keyboard *keyboard);

include/view.h

@@ -186,6 +186,12 @@ enum lab_view_criteria {
 	LAB_VIEW_CRITERIA_NO_SKIP_WINDOW_SWITCHER = 1 << 2,
 };
 
+/**
+ * view_from_wlr_surface() - returns the view associated with a
+ * wlr_surface, or NULL if the surface has no associated view.
+ */
+struct view *view_from_wlr_surface(struct wlr_surface *surface);
+
 /**
  * for_each_view() - iterate over all views which match criteria
  * @view: Iterator.
@@ -257,8 +263,7 @@ bool view_isfocusable(struct view *view);
 bool view_inhibits_keybinds(struct view *view);
 void view_toggle_keybinds(struct view *view);
 
-void view_focus(struct view *view);
-void view_defocus(struct view *view);
+void view_set_activated(struct view *view, bool activated);
 void view_set_output(struct view *view, struct output *output);
 void view_close(struct view *view);
 

src/action.c

@@ -503,7 +503,7 @@ view_for_action(struct view *activator, struct server *server,
 		return ctx.view;
 	}
 	default:
-		return desktop_focused_view(server);
+		return server->focused_view;
 	}
 }
 

src/cursor.c

@@ -602,7 +602,7 @@ create_constraint(struct wl_listener *listener, void *data)
 	constraint->destroy.notify = destroy_constraint;
 	wl_signal_add(&wlr_constraint->events.destroy, &constraint->destroy);
 
-	struct view *view = desktop_focused_view(server);
+	struct view *view = server->focused_view;
 	if (view && view->surface == wlr_constraint->surface) {
 		constrain_cursor(server, wlr_constraint);
 	}

src/desktop.c

@@ -74,7 +74,10 @@ desktop_focus_view(struct view *view, bool raise)
 		workspaces_switch_to(view->workspace, /*update_focus*/ false);
 	}
 
-	view_focus(view);
+	struct seat *seat = &server->seat;
+	if (view->surface != seat->seat->keyboard_state.focused_surface) {
+		seat_focus_surface(seat, view->surface);
+	}
 
 	if (raise) {
 		view_move_to_front(view);
@@ -147,7 +150,7 @@ desktop_cycle_view(struct server *server, struct view *start_view,
 
 	if (!start_view) {
 		start_view = first_view(server);
-		if (!start_view || start_view != desktop_focused_view(server)) {
+		if (!start_view || start_view != server->focused_view) {
 			return start_view;  /* may be NULL */
 		}
 	}
@@ -206,32 +209,6 @@ desktop_topmost_mapped_view(struct server *server)
 	return NULL;
 }
 
-struct view *
-desktop_focused_view(struct server *server)
-{
-	struct seat *seat = &server->seat;
-	struct wlr_surface *focused_surface =
-		seat->seat->keyboard_state.focused_surface;
-	struct view *focused_view = NULL;
-
-	if (focused_surface) {
-		struct view *view;
-		wl_list_for_each(view, &server->views, link) {
-			if (view->surface == focused_surface) {
-				focused_view = view;
-				break;
-			}
-		}
-	}
-
-	/* warn so we can identify cases where this occurs */
-	if (focused_view != server->focused_view) {
-		wlr_log(WLR_ERROR, "server->focused_view is out of sync");
-	}
-
-	return focused_view;
-}
-
 void
 desktop_focus_topmost_mapped_view(struct server *server)
 {
@@ -242,12 +219,8 @@ desktop_focus_topmost_mapped_view(struct server *server)
 		/*
 		 * Defocus previous focused surface/view if no longer
 		 * focusable (e.g. unmapped or on a different workspace).
-		 * Note than a non-view surface may have been focused.
 		 */
 		seat_focus_surface(&server->seat, NULL);
-		if (server->focused_view) {
-			view_defocus(server->focused_view);
-		}
 	}
 }
 

src/keyboard.c

@@ -94,7 +94,7 @@ handle_keybinding(struct server *server, uint32_t modifiers, xkb_keysym_t sym, x
 			continue;
 		}
 		if (server->seat.nr_inhibited_keybind_views
-				&& view_inhibits_keybinds(desktop_focused_view(server))
+				&& view_inhibits_keybinds(server->focused_view)
 				&& !actions_contain_toggle_keybinds(&keybind->actions)) {
 			continue;
 		}

src/seat.c

@@ -11,6 +11,7 @@
 #include "common/mem.h"
 #include "key-state.h"
 #include "labwc.h"
+#include "view.h"
 
 static void
 input_device_destroy(struct wl_listener *listener, void *data)
@@ -335,6 +336,26 @@ new_virtual_keyboard(struct wl_listener *listener, void *data)
 	seat_add_device(seat, input);
 }
 
+static void
+focus_change_notify(struct wl_listener *listener, void *data)
+{
+	struct seat *seat = wl_container_of(listener, seat, focus_change);
+	struct wlr_seat_keyboard_focus_change_event *event = data;
+	struct server *server = seat->server;
+	struct view *view = event->new_surface ?
+		view_from_wlr_surface(event->new_surface) : NULL;
+
+	if (view != server->focused_view) {
+		if (server->focused_view) {
+			view_set_activated(server->focused_view, false);
+		}
+		if (view) {
+			view_set_activated(view, true);
+		}
+		server->focused_view = view;
+	}
+}
+
 void
 seat_init(struct server *server)
 {
@@ -353,6 +374,10 @@ seat_init(struct server *server)
 	seat->new_input.notify = new_input_notify;
 	wl_signal_add(&server->backend->events.new_input, &seat->new_input);
 
+	seat->focus_change.notify = focus_change_notify;
+	wl_signal_add(&seat->seat->keyboard_state.events.focus_change,
+		&seat->focus_change);
+
 	seat->virtual_pointer = wlr_virtual_pointer_manager_v1_create(
 		server->wl_display);
 	wl_signal_add(&seat->virtual_pointer->events.new_virtual_pointer,
@@ -382,6 +407,7 @@ seat_finish(struct server *server)
 {
 	struct seat *seat = &server->seat;
 	wl_list_remove(&seat->new_input.link);
+	wl_list_remove(&seat->focus_change.link);
 
 	struct input *input, *next;
 	wl_list_for_each_safe(input, next, &seat->inputs, link) {

src/view.c

@@ -2,6 +2,7 @@
 #include <assert.h>
 #include <stdio.h>
 #include <strings.h>
+#include <wlr/xwayland.h>
 #include "common/mem.h"
 #include "common/scene-helpers.h"
 #include "labwc.h"
@@ -19,6 +20,34 @@
 #define LAB_FALLBACK_WIDTH  640
 #define LAB_FALLBACK_HEIGHT 480
 
+struct view *
+view_from_wlr_surface(struct wlr_surface *surface)
+{
+	assert(surface);
+	/*
+	 * TODO:
+	 * - find a way to get rid of xdg/xwayland-specific stuff
+	 * - look up root/toplevel surface if passed a subsurface?
+	 */
+	if (wlr_surface_is_xdg_surface(surface)) {
+		struct wlr_xdg_surface *xdg_surface =
+			wlr_xdg_surface_from_wlr_surface(surface);
+		if (xdg_surface) {
+			return xdg_surface->data;
+		}
+	}
+#if HAVE_XWAYLAND
+	if (wlr_surface_is_xwayland_surface(surface)) {
+		struct wlr_xwayland_surface *xsurface =
+			wlr_xwayland_surface_from_wlr_surface(surface);
+		if (xsurface) {
+			return xsurface->data;
+		}
+	}
+#endif
+	return NULL;
+}
+
 static bool
 matches_criteria(struct view *view, enum lab_view_criteria criteria)
 {
@@ -174,9 +203,10 @@ view_discover_output(struct view *view)
 		view->current.y + view->current.height / 2);
 }
 
-static void
-_view_set_activated(struct view *view, bool activated)
+void
+view_set_activated(struct view *view, bool activated)
 {
+	assert(view);
 	ssd_set_active(view->ssd, activated);
 	if (view->impl->set_activated) {
 		view->impl->set_activated(view, activated);
@@ -187,52 +217,6 @@ _view_set_activated(struct view *view, bool activated)
 	}
 }
 
-/*
- * Give the view keyboard focus and mark it active. This function should
- * only be called by desktop_focus_view(), which contains additional
- * checks to make sure it's okay to give focus.
- */
-void
-view_focus(struct view *view)
-{
-	assert(view);
-	/* Update seat focus */
-	struct seat *seat = &view->server->seat;
-	if (view->surface != seat->seat->keyboard_state.focused_surface) {
-		seat_focus_surface(seat, view->surface);
-	}
-	/* Update active view */
-	if (view != view->server->focused_view) {
-		if (view->server->focused_view) {
-			_view_set_activated(view->server->focused_view, false);
-		}
-		_view_set_activated(view, true);
-		view->server->focused_view = view;
-	}
-}
-
-/*
- * Take keyboard focus from the view and mark it inactive. It's rarely
- * necessary to call this function directly; usually it's better to
- * focus a different view instead by calling something like
- * desktop_focus_topmost_mapped_view().
- */
-void
-view_defocus(struct view *view)
-{
-	assert(view);
-	/* Update seat focus */
-	struct seat *seat = &view->server->seat;
-	if (view->surface == seat->seat->keyboard_state.focused_surface) {
-		seat_focus_surface(seat, NULL);
-	}
-	/* Update active view */
-	if (view == view->server->focused_view) {
-		_view_set_activated(view, false);
-		view->server->focused_view = NULL;
-	}
-}
-
 void
 view_set_output(struct view *view, struct output *output)
 {
@@ -408,7 +392,6 @@ _minimize(struct view *view, bool minimized)
 	view->minimized = minimized;
 	if (minimized) {
 		view->impl->unmap(view, /* client_request */ false);
-		view_defocus(view);
 	} else {
 		view->impl->map(view);
 	}

src/workspaces.c

@@ -287,7 +287,7 @@ workspaces_switch_to(struct workspace *target, bool update_focus)
 	 * Only refocus if the focus is not already on an always-on-top view.
 	 */
 	if (update_focus) {
-		struct view *view = desktop_focused_view(server);
+		struct view *view = server->focused_view;
 		if (!view || !view_is_always_on_top(view)) {
 			desktop_focus_topmost_mapped_view(server);
 		}