Some bug fixes

1. The "crash when exiting an application while moving it" bug. See https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3372
2. The crash when there's no previous view to focus. This wasn't a problem before the migration to the scene graph API due to a logic error on my part.
3. The crash if <margins> is missing from rc.xml.
4. I'm now reusing code from focus_view() in seat_focus_surface().
5. I'm now using the dimensions of the output layout box instead of the current view (which was clearly wrong) for unconstraining layer-shell popups.
6. I fixed setting the background color, so that it won't interfere with the layer_shell helper.

include/waybox/output.h

@@ -23,9 +23,8 @@ struct wb_output {
 		struct wlr_scene_node *shell_top;
 	} layers;
 
-#if !WLR_CHECK_VERSION(0, 16, 0)
-	struct wlr_scene_rect *scene_rect;
-#endif
+	struct wlr_scene_rect *background;
+	struct wlr_box geometry;
 
 	struct wl_listener destroy;
 	struct wl_listener frame;

include/waybox/seat.h

@@ -30,6 +30,7 @@ struct wb_keyboard {
 
 struct wb_server;
 struct wb_seat *wb_seat_create(struct wb_server *server);
+void seat_focus_surface(struct wb_seat *seat, struct wlr_surface *surface);
 void seat_set_focus_layer(struct wb_seat *seat, struct wlr_layer_surface_v1 *layer);
 void wb_seat_destroy(struct wb_seat *seat);
 #endif

waybox/config.c

@@ -3,6 +3,12 @@
 
 #include "config.h"
 
+static unsigned long strtoulong(char *s) {
+	if (s)
+		return strtoul(s, (char **) NULL, 10);
+	else return 0;
+}
+
 static char *parse_xpath_expr(char *expr, xmlXPathContextPtr ctxt) {
 	xmlXPathObjectPtr object = xmlXPathEvalExpression((xmlChar *) expr, ctxt);
 	if (object == NULL) {
@@ -175,10 +181,10 @@ bool init_config(struct wb_server *server) {
 		return false;
 	}
 
-	config->margins.bottom = strtoul(parse_xpath_expr("//ob:margins/ob:bottom", ctxt), NULL, 10);
-	config->margins.left = strtoul(parse_xpath_expr("//ob:margins/ob:left", ctxt), NULL, 10);
-	config->margins.right = strtoul(parse_xpath_expr("//ob:margins/ob:right", ctxt), NULL, 10);
-	config->margins.top = strtoul(parse_xpath_expr("//ob:margins/ob:top", ctxt), NULL, 10);
+	config->margins.bottom = strtoulong(parse_xpath_expr("//ob:margins/ob:bottom", ctxt));
+	config->margins.left = strtoulong(parse_xpath_expr("//ob:margins/ob:left", ctxt));
+	config->margins.right = strtoulong(parse_xpath_expr("//ob:margins/ob:right", ctxt));
+	config->margins.top = strtoulong(parse_xpath_expr("//ob:margins/ob:top", ctxt));
 
 	server->config = config;
 

waybox/cursor.c

@@ -7,8 +7,10 @@ static void process_cursor_move(struct wb_server *server) {
 	struct wb_view *view = server->grabbed_view;
 	view->current_position.x = server->cursor->cursor->x - server->grab_x;
 	view->current_position.y = server->cursor->cursor->y - server->grab_y;
-	wlr_scene_node_set_position(view->scene_node,
-			view->current_position.x, view->current_position.y);
+	if (view->scene_node->parent->type == WLR_SCENE_NODE_ROOT) {
+		wlr_scene_node_set_position(view->scene_node,
+				view->current_position.x, view->current_position.y);
+	}
 }
 
 static void process_cursor_resize(struct wb_server *server) {

waybox/layer_shell.c

@@ -237,12 +237,11 @@ static void popup_unconstrain(struct wb_layer_popup *popup) {
 
 	/* the output box expressed in the coordinate system of the toplevel parent
 	 * of the popup */
-	struct wb_view *view = wl_container_of(output->server->views.next, view, link);
 	struct wlr_box output_toplevel_sx_box = {
-		.x = view->current_position.x - lx,
-		.y = view->current_position.y - ly,
-		.width = output->wlr_output->width,
-		.height = output->wlr_output->height,
+		.x = output->geometry.x - lx,
+		.y = output->geometry.y - ly,
+		.width = output->geometry.width,
+		.height = output->geometry.height,
 	};
 
 	wlr_xdg_popup_unconstrain_from_box(wlr_popup, &output_toplevel_sx_box);

waybox/output.c

@@ -1,20 +1,30 @@
 #include "waybox/output.h"
 
 void output_frame_notify(struct wl_listener *listener, void *data) {
+	/* This function is called every time an output is ready to display a frame,
+	 * generally at the output's refresh rate (e.g. 60Hz). */
 	struct wb_output *output = wl_container_of(listener, output, frame);
 	struct wlr_scene *scene = output->server->scene;
 
 	struct wlr_scene_output *scene_output = wlr_scene_get_scene_output(
 		scene, output->wlr_output);
 
-#if !WLR_CHECK_VERSION(0, 16, 0)
-	wlr_scene_rect_set_size(output->scene_rect,
-			output->wlr_output->width, output->wlr_output->height);
+#if WLR_CHECK_VERSION(0, 16, 0)
+	wlr_output_layout_get_box(output->server->output_layout,
+			output->wlr_output, &output->geometry);
+#else
+	output->geometry = *wlr_output_layout_get_box(
+			output->server->output_layout, output->wlr_output);
 #endif
+	/* Update the background for the current output size. */
+	wlr_scene_rect_set_size(output->background,
+			output->geometry.width, output->geometry.height);
 
 	/* Render the scene if needed and commit the output */
 	wlr_scene_output_commit(scene_output);
 
+	/* This lets the client know that we've displayed that frame and it can
+	 * prepare another one now if it likes. */
 	struct timespec now;
 	clock_gettime(CLOCK_MONOTONIC, &now);
 	wlr_scene_output_send_frame_done(scene_output, &now);
@@ -65,12 +75,10 @@ void new_output_notify(struct wl_listener *listener, void *data) {
 	output->wlr_output = wlr_output;
 	wlr_output->data = output;
 
-#if !WLR_CHECK_VERSION(0, 16, 0)
-	/* Allows setting the traditional background color.  However, it
-	 * interferes with the wlr_scene layer shell helper in 0.16.0+. */
+	/* Set the background color */
 	float color[4] = {0.1875, 0.1875, 0.1875, 1.0};
-	output->scene_rect = wlr_scene_rect_create(&server->scene->node, 0, 0, color);
-#endif
+	output->background = wlr_scene_rect_create(&server->scene->node, 0, 0, color);
+	wlr_scene_node_lower_to_bottom(&output->background->node);
 
 	/* Initializes the layers */
 	size_t num_layers = sizeof(output->layers) / sizeof(struct wlr_scene_node *);

waybox/seat.c

@@ -274,7 +274,8 @@ void seat_focus_surface(struct wb_seat *seat, struct wlr_surface *surface) {
 		wlr_seat_keyboard_notify_clear_focus(seat->seat);
 		return;
 	}
-	struct wlr_keyboard *kb = (struct wlr_keyboard *) seat->keyboards.next;
+
+	struct wlr_keyboard *kb = wlr_seat_get_keyboard(seat->seat);
 	wlr_seat_keyboard_notify_enter(seat->seat, surface, kb->keycodes,
 		kb->num_keycodes, &kb->modifiers);
 }
@@ -327,6 +328,7 @@ struct wb_seat *wb_seat_create(struct wb_server *server) {
 }
 
 void wb_seat_destroy(struct wb_seat *seat) {
+	wl_list_remove(&seat->keyboards);
 	wl_list_remove(&seat->request_set_primary_selection.link);
 	wl_list_remove(&seat->request_set_selection.link);
 	wlr_seat_destroy(seat->seat);

waybox/xdg_shell.c

@@ -52,7 +52,6 @@ void focus_view(struct wb_view *view, struct wlr_surface *surface) {
 		wlr_xdg_toplevel_set_activated(previous, false);
 #endif
 	}
-	struct wlr_keyboard *keyboard = wlr_seat_get_keyboard(seat);
 	/* Move the view to the front */
 	wlr_scene_node_raise_to_top(view->scene_node);
 	wl_list_remove(&view->link);
@@ -68,8 +67,7 @@ void focus_view(struct wb_view *view, struct wlr_surface *surface) {
 	 * track of this and automatically send key events to the appropriate
 	 * clients without additional work on your part.
 	 */
-	wlr_seat_keyboard_notify_enter(seat, view->xdg_toplevel->base->surface,
-		keyboard->keycodes, keyboard->num_keycodes, &keyboard->modifiers);
+	seat_focus_surface(server->seat, view->xdg_toplevel->base->surface);
 }
 
 static struct wlr_box get_usable_area(struct wb_view *view) {
@@ -126,15 +124,9 @@ static void xdg_toplevel_unmap(struct wl_listener *listener, void *data) {
 	if (view->xdg_toplevel->base->role != WLR_XDG_SURFACE_ROLE_TOPLEVEL)
 		return;
 
+	/* Focus the next view, if any. */
 	struct wb_view *next_view = wl_container_of(view->link.next, next_view, link);
-	/* If the current view is mapped, focus it. */
-	if (view->scene_node->state.enabled) {
-		wlr_log(WLR_INFO, "%s: %s", _("Focusing current view"),
-				view->xdg_toplevel->app_id);
-		focus_view(view, view->xdg_toplevel->base->surface);
-	}
-	/* Otherwise, focus the next view, if any. */
-	else if (next_view && next_view->scene_node && next_view->scene_node->state.enabled) {
+	if (next_view && next_view->scene_node && next_view->scene_node->state.enabled) {
 		wlr_log(WLR_INFO, "%s: %s", _("Focusing next view"),
 				next_view->xdg_toplevel->app_id);
 		focus_view(next_view, next_view->xdg_toplevel->base->surface);
@@ -148,6 +140,7 @@ static void xdg_toplevel_destroy(struct wl_listener *listener, void *data) {
 	wl_list_remove(&view->map.link);
 	wl_list_remove(&view->unmap.link);
 	wl_list_remove(&view->destroy.link);
+	wl_list_remove(&view->new_popup.link);
 
 	if (view->xdg_toplevel->base->role == WLR_XDG_SURFACE_ROLE_TOPLEVEL) {
 		wl_list_remove(&view->request_minimize.link);
@@ -269,22 +262,18 @@ static void xdg_toplevel_request_resize(
 static void handle_new_popup(struct wl_listener *listener, void *data) {
 	struct wlr_xdg_popup *popup = data;
 	struct wb_view *view = wl_container_of(listener, view, new_popup);
-	struct wlr_output_layout *output_layout = view->server->output_layout;
 
-	struct wlr_output *wlr_output = wlr_output_layout_output_at(output_layout,
+	struct wlr_output *wlr_output = wlr_output_layout_output_at(
+			view->server->output_layout,
 			view->current_position.x + popup->geometry.x,
 			view->current_position.y + popup->geometry.y);
-	struct wlr_box output_box;
-#if WLR_CHECK_VERSION(0, 16, 0)
-	wlr_output_layout_get_box(output_layout, wlr_output, &output_box);
-#else
-	output_box = (*wlr_output_layout_get_box(output_layout, wlr_output));
-#endif
+	struct wb_output *output = wlr_output->data;
+
 	struct wlr_box output_toplevel_box = {
-		.x = output_box.x - view->current_position.x,
-		.y = output_box.y - view->current_position.y,
-		.width = output_box.width,
-		.height = output_box.height,
+		.x = output->geometry.x - view->current_position.x,
+		.y = output->geometry.y - view->current_position.y,
+		.width = output->geometry.width,
+		.height = output->geometry.height,
 	};
 	wlr_xdg_popup_unconstrain_from_box(popup, &output_toplevel_box);
 }