xdg-shell: fix inert xdg_surface handling

Closes: https://github.com/swaywm/sway/issues/4834
Closes: https://github.com/swaywm/wlroots/issues/1890

include/wlr/types/wlr_xdg_shell.h

@@ -244,6 +244,11 @@ struct wlr_xdg_toplevel_show_window_menu_event {
 
 struct wlr_xdg_shell *wlr_xdg_shell_create(struct wl_display *display);
 
+/** Returns the wlr_xdg_surface from an xdg_surface resource.
+ *
+ * Aborts if the resource doesn't have the correct type. Returns NULL if the
+ * resource is inert.
+ */
 struct wlr_xdg_surface *wlr_xdg_surface_from_resource(
 		struct wl_resource *resource);
 struct wlr_xdg_surface *wlr_xdg_surface_from_popup_resource(

types/xdg_shell/wlr_xdg_surface.c

@@ -96,6 +96,9 @@ void unmap_xdg_surface(struct wlr_xdg_surface *surface) {
 static void xdg_surface_handle_ack_configure(struct wl_client *client,
 		struct wl_resource *resource, uint32_t serial) {
 	struct wlr_xdg_surface *surface = wlr_xdg_surface_from_resource(resource);
+	if (surface == NULL) {
+		return;
+	}
 
 	if (surface->role == WLR_XDG_SURFACE_ROLE_NONE) {
 		wl_resource_post_error(surface->resource,
@@ -236,6 +239,9 @@ static void xdg_surface_handle_get_popup(struct wl_client *client,
 		wlr_xdg_surface_from_resource(resource);
 	struct wlr_xdg_surface *parent =
 		wlr_xdg_surface_from_resource(parent_resource);
+	if (xdg_surface == NULL) {
+		return; // TODO: create an inert xdg_popup
+	}
 	struct wlr_xdg_positioner_resource *positioner =
 		get_xdg_positioner_from_resource(positioner_resource);
 	create_xdg_popup(xdg_surface, parent, positioner, id);
@@ -245,6 +251,9 @@ static void xdg_surface_handle_get_toplevel(struct wl_client *client,
 		struct wl_resource *resource, uint32_t id) {
 	struct wlr_xdg_surface *xdg_surface =
 		wlr_xdg_surface_from_resource(resource);
+	if (xdg_surface == NULL) {
+		return; // TODO: create an inert xdg_toplevel
+	}
 	create_xdg_toplevel(xdg_surface, id);
 }
 
@@ -252,6 +261,9 @@ static void xdg_surface_handle_set_window_geometry(struct wl_client *client,
 		struct wl_resource *resource, int32_t x, int32_t y, int32_t width,
 		int32_t height) {
 	struct wlr_xdg_surface *surface = wlr_xdg_surface_from_resource(resource);
+	if (surface == NULL) {
+		return;
+	}
 
 	if (surface->role == WLR_XDG_SURFACE_ROLE_NONE) {
 		wl_resource_post_error(surface->resource,
@@ -277,6 +289,9 @@ static void xdg_surface_handle_set_window_geometry(struct wl_client *client,
 static void xdg_surface_handle_destroy(struct wl_client *client,
 		struct wl_resource *resource) {
 	struct wlr_xdg_surface *surface = wlr_xdg_surface_from_resource(resource);
+	if (surface == NULL) {
+		return;
+	}
 
 	if (surface->role != WLR_XDG_SURFACE_ROLE_NONE) {
 		wlr_log(WLR_ERROR, "Tried to destroy an xdg_surface before its role "
@@ -502,7 +517,6 @@ void destroy_xdg_surface(struct wlr_xdg_surface *surface) {
 
 struct wlr_xdg_surface *wlr_xdg_surface_from_resource(
 		struct wl_resource *resource) {
-	// TODO: Double check that all of the callers can deal with NULL
 	if (!resource) {
 		return NULL;
 	}