xdg-shell: add wlr_xdg_{toplevel,popup}_try_from_wlr_surface()

Convenience helpers for compositors. Saves them the trouble of
manually checking the role (and if they forget to do so, prevents
an invalid cast).

include/wlr/types/wlr_xdg_shell.h

@@ -485,6 +485,24 @@ struct wlr_surface *wlr_xdg_surface_popup_surface_at(
  */
 struct wlr_xdg_surface *wlr_xdg_surface_try_from_wlr_surface(struct wlr_surface *surface);
 
+/**
+ * Get a struct wlr_xdg_toplevel from a struct wlr_surface.
+ *
+ * Returns NULL if the surface doesn't have the xdg_surface role, the
+ * xdg_surface is not a toplevel, or the xdg_surface/xdg_toplevel objects have
+ * been destroyed.
+ */
+struct wlr_xdg_toplevel *wlr_xdg_toplevel_try_from_wlr_surface(struct wlr_surface *surface);
+
+/**
+ * Get a struct wlr_xdg_popup from a struct wlr_surface.
+ *
+ * Returns NULL if the surface doesn't have the xdg_surface role, the
+ * xdg_surface is not a popup, or the xdg_surface/xdg_popup objects have
+ * been destroyed.
+ */
+struct wlr_xdg_popup *wlr_xdg_popup_try_from_wlr_surface(struct wlr_surface *surface);
+
 /**
  * Get the surface geometry.
  *

types/xdg_shell/wlr_xdg_popup.c

@@ -261,6 +261,14 @@ struct wlr_xdg_popup *wlr_xdg_popup_from_resource(
 	return wl_resource_get_user_data(resource);
 }
 
+struct wlr_xdg_popup *wlr_xdg_popup_try_from_wlr_surface(struct wlr_surface *surface) {
+	struct wlr_xdg_surface *xdg_surface = wlr_xdg_surface_try_from_wlr_surface(surface);
+	if (xdg_surface == NULL || xdg_surface->role != WLR_XDG_SURFACE_ROLE_POPUP) {
+		return NULL;
+	}
+	return xdg_surface->popup;
+}
+
 static void xdg_popup_handle_grab(struct wl_client *client,
 		struct wl_resource *resource, struct wl_resource *seat_resource,
 		uint32_t serial) {

types/xdg_shell/wlr_xdg_toplevel.c

@@ -158,6 +158,14 @@ struct wlr_xdg_toplevel *wlr_xdg_toplevel_from_resource(
 	return wl_resource_get_user_data(resource);
 }
 
+struct wlr_xdg_toplevel *wlr_xdg_toplevel_try_from_wlr_surface(struct wlr_surface *surface) {
+	struct wlr_xdg_surface *xdg_surface = wlr_xdg_surface_try_from_wlr_surface(surface);
+	if (xdg_surface == NULL || xdg_surface->role != WLR_XDG_SURFACE_ROLE_TOPLEVEL) {
+		return NULL;
+	}
+	return xdg_surface->toplevel;
+}
+
 static void handle_parent_unmap(struct wl_listener *listener, void *data) {
 	struct wlr_xdg_toplevel *toplevel =
 		wl_container_of(listener, toplevel, parent_unmap);