xwayland: populate window_properties in json for views

window_properties is documented to contain a subset of the X11 properties
of a window (its title, class, instance, role, and transient ID). This
commit adds the missing json object from the get_tree output for
xwayland windows only.

This is a follow-up of #2911.

Signed-off-by: Franklin "Snaipe" Mathieu <me@snai.pe>

sway/ipc-json.c

@@ -266,6 +266,23 @@ static void ipc_json_describe_view(struct sway_container *c, json_object *object
 	if (c->view->type == SWAY_VIEW_XWAYLAND) {
 		json_object_object_add(object, "window",
 				json_object_new_int(view_get_x11_window_id(c->view)));
+
+		json_object *window_props = json_object_new_object();
+
+		json_object_object_add(window_props, "class",
+				class ? json_object_new_string(class) : NULL);
+		const char *instance = view_get_instance(c->view);
+		json_object_object_add(window_props, "instance",
+				instance ? json_object_new_string(instance) : NULL);
+		json_object_object_add(window_props, "title",
+				c->title ? json_object_new_string(c->title) : NULL);
+		const char *role = view_get_window_role(c->view);
+		if (role) {
+			json_object_object_add(window_props, "window_role",
+					json_object_new_string(role));
+		}
+
+		json_object_object_add(object, "window_properties", window_props);
 	}
 #endif
 }