tree/view: Make foreign-toplevel app_id fallback to class

It is not a part of the foreign-toplevel-management protocol to get the
class of a toplevel, only for getting the app_id.
For xwayland clients this is an issue because that means that you cannot
identify what application the toplevel refers to which is the point of
the app_id property.

By falling back to class when an app_id does not exist solves this problem.

Phoc also uses app_id and class interchangeably in their implementation
of foreign-toplevel-management, in fact they always do that and not only
for just this protocol.
https://source.puri.sm/Librem5/phoc/-/blob/c8d8a4c5440a6c1647b09dbd3bba7999f9cd433c/src/xwayland.c#L236

1 files changed, 6 insertions, 2 deletions

diff --git a/sway/tree/view.c b/sway/tree/view.c
index fb397c42..53c11a32 100644
--- a/sway/tree/view.c
+++ b/sway/tree/view.c
@@ -738,10 +738,14 @@ void view_map(struct sway_view *view, struct wlr_surface *wlr_surface,
                 input_manager_set_focus(&view->container->node);
         }
 
-        const char *app_id = view_get_app_id(view);
-        if (app_id != NULL) {
+        const char *app_id;
+        const char *class;
+        if ((app_id = view_get_app_id(view)) != NULL) {
                 wlr_foreign_toplevel_handle_v1_set_app_id(
                                 view->foreign_toplevel, app_id);
+        } else if ((class = view_get_class(view)) != NULL) {
+                wlr_foreign_toplevel_handle_v1_set_app_id(
+                                view->foreign_toplevel, class);
         }
 }