desktop: enforce followMouse focus policy more strictly

When followMouse=yes, prevent stealing focus from another view under
the cursor. The requested view *is* allowed to take focus if it ends up
under the cursor after raising, or if there is no view under the cursor
at all. (Non-view surfaces aren't currently considered.)

v2: allow focusing a new/raised view appearing under the cursor
v3: allow focusing a sub-view/sibling of the requested view
v4: fix new xdg-shell views under mouse not being focused
v5: allow focus if no other view is focused; rebase

include/labwc.h

@@ -476,10 +476,12 @@ void xdg_shell_finish(struct server *server);
 void desktop_focus_view(struct view *view, bool raise);
 
 /**
- * desktop_focus_view_or_surface() - like desktop_focus_view() but can
+ * desktop_focus_for_cursor_update() - like desktop_focus_view() but can
- * also focus other (e.g. xwayland-unmanaged) surfaces
+ * also focus other (e.g. xwayland-unmanaged) surfaces.
+ *
+ * Used only for cursor-driven focus updates.
  */
-void desktop_focus_view_or_surface(struct seat *seat, struct view *view,
+void desktop_focus_for_cursor_update(struct seat *seat, struct view *view,
 	struct wlr_surface *surface, bool raise);
 
 void desktop_arrange_all_views(struct server *server);

src/desktop.c

@@ -58,8 +58,8 @@ set_or_offer_focus(struct view *view)
 	}
 }
 
-void
+static void
-desktop_focus_view(struct view *view, bool raise)
+_desktop_focus_view(struct view *view, bool raise, bool for_cursor_update)
 {
 	assert(view);
 	/*
@@ -100,6 +100,28 @@ desktop_focus_view(struct view *view, bool raise)
 		view_move_to_front(view);
 	}
 
+	/*
+	 * When followMouse=yes, prevent stealing focus from another
+	 * view under the cursor. The requested view *is* allowed to
+	 * take focus if it ends up under the cursor after raising, or
+	 * if there is no view under the cursor at all.
+	 *
+	 * If view_move_to_front() also raised child/sibling views,
+	 * then focus the sibling that's under the cursor.
+	 */
+	if (rc.focus_follow_mouse && !for_cursor_update) {
+		struct cursor_context ctx = get_cursor_context(view->server);
+		if (ctx.view && view_get_root(ctx.view) == view_get_root(view)) {
+			view = ctx.view;
+		} else if (ctx.view) {
+			/*
+			 * Do not steal focus from an unrelated view.
+			 * TODO: consider non-view surfaces also?
+			 */
+			return;
+		}
+	}
+
 	/*
 	 * If any child/sibling of the view is a modal dialog, focus
 	 * the dialog instead. It does not need to be raised separately
@@ -109,14 +131,20 @@ desktop_focus_view(struct view *view, bool raise)
 	set_or_offer_focus(dialog ? dialog : view);
 }
 
+void
+desktop_focus_view(struct view *view, bool raise)
+{
+	_desktop_focus_view(view, raise, /*for_cursor_update*/ false);
+}
+
 /* TODO: focus layer-shell surfaces also? */
 void
-desktop_focus_view_or_surface(struct seat *seat, struct view *view,
+desktop_focus_for_cursor_update(struct seat *seat, struct view *view,
 		struct wlr_surface *surface, bool raise)
 {
 	assert(view || surface);
 	if (view) {
-		desktop_focus_view(view, raise);
+		_desktop_focus_view(view, raise, /*for_cursor_update*/ true);
 #if HAVE_XWAYLAND
 	} else {
 		struct wlr_xwayland_surface *xsurface =

src/input/cursor.c

@@ -639,7 +639,7 @@ cursor_process_motion(struct server *server, uint32_t time, double *sx, double *
 		 * If followMouse=yes, update the keyboard focus when the
 		 * cursor enters a surface
 		 */
-		desktop_focus_view_or_surface(seat,
+		desktop_focus_for_cursor_update(seat,
 			view_from_wlr_surface(new_focused_surface),
 			new_focused_surface, rc.raise_on_focus);
 	}
@@ -659,7 +659,7 @@ _cursor_update_focus(struct server *server)
 		 * Always focus the surface below the cursor when
 		 * followMouse=yes and followMouseRequiresMovement=no.
 		 */
-		desktop_focus_view_or_surface(&server->seat, ctx.view,
+		desktop_focus_for_cursor_update(&server->seat, ctx.view,
 			ctx.surface, rc.raise_on_focus);
 	}
 
@@ -1102,7 +1102,7 @@ cursor_process_button_press(struct seat *seat, uint32_t button, uint32_t time_ms
 		}
 #ifdef HAVE_XWAYLAND
 	} else if (ctx.type == LAB_SSD_UNMANAGED) {
-		desktop_focus_view_or_surface(seat, NULL, ctx.surface,
+		desktop_focus_for_cursor_update(seat, NULL, ctx.surface,
 			/*raise*/ false);
 #endif
 	}

src/view-impl-common.c

@@ -11,7 +11,6 @@
 void
 view_impl_map(struct view *view)
 {
-	desktop_focus_view(view, /*raise*/ true);
 	view_update_title(view);
 	view_update_app_id(view);
 	if (!view->been_mapped) {

src/xdg.c

@@ -217,8 +217,18 @@ handle_commit(struct wl_listener *listener, void *data)
 	}
 
 	if (update_required) {
+		bool was_empty = wlr_box_empty(current);
 		view_impl_apply_geometry(view, size.width, size.height);
 
+		/*
+		 * Try to focus the view once it has a valid surface
+		 * size. Before this point, the under-mouse checks in
+		 * desktop_focus_view() may fail.
+		 */
+		if (was_empty && !wlr_box_empty(&size)) {
+			desktop_focus_view(view, /*raise*/ true);
+		}
+
 		/*
 		 * Some views (e.g., terminals that scale as multiples of rows
 		 * and columns, or windows that impose a fixed aspect ratio),

src/xwayland.c

@@ -826,14 +826,14 @@ xwayland_view_map(struct view *view)
 
 	/*
 	 * If the view was focused (on the xwayland server side) before
-	 * being mapped, update the seat focus now. Note that this only
+	 * being mapped, just update the seat focus. Otherwise, try to
-	 * really matters in the case of Globally Active input windows.
+	 * focus the view now.
-	 * In all other cases, it's redundant since view_impl_map()
-	 * results in the view being focused anyway.
 	 */
 	if (xwayland_view->focused_before_map) {
 		xwayland_view->focused_before_map = false;
 		seat_focus_surface(&view->server->seat, view->surface);
+	} else {
+		desktop_focus_view(view, /*raise*/ true);
 	}
 
 	view_impl_map(view);