fix: panels stay above windows; don't force SSD on CSD-only (GTK) clients

include/waybox/server.h

@@ -45,6 +45,10 @@ struct wb_server {
 	struct wlr_xdg_output_manager_v1 *output_manager;
 	struct wlr_renderer *renderer;
 	struct wlr_scene *scene;
+	/* Container for all xdg toplevels, kept at a fixed z between the lower
+	 * (background, bottom) and upper (top, overlay) layer-shell trees so panels
+	 * like Waybar correctly render above ordinary windows. */
+	struct wlr_scene_tree *toplevel_tree;
 	struct wlr_scene_output_layout *scene_layout;
 	struct wlr_session *session;
 	struct wlr_subcompositor *subcompositor;

waybox/decoration.cpp

@@ -13,14 +13,22 @@
  * negotiation honours DecorMode::Full and client SSD requests. */
 static constexpr bool kSsdAvailable = true;
 
-/* Whether this toplevel should currently wear a server-side frame: the
- * negotiated decoration is server-side and it is not fullscreen. */
+/* Whether this toplevel should currently wear a server-side frame.
+ *
+ * SSD requires the client to participate in the xdg-decoration protocol: a
+ * client that never created a decoration object (notably GTK, which is
+ * CSD-only and always draws its own titlebar + shadow) cannot be told to drop
+ * its decorations, so imposing an SSD frame on it produces conflicting double
+ * decorations. We therefore only wear a frame when the client bound the
+ * decoration protocol for this toplevel; for such clients we then honour
+ * DecorMode and the client's requested mode. */
 static bool toplevel_wants_ssd(struct wb_toplevel *toplevel) {
 	if (toplevel->xdg_toplevel->current.fullscreen)
 		return false;
-	bool client_wants_ssd = toplevel->decoration != nullptr &&
-			toplevel->decoration->requested_mode ==
-					WLR_XDG_TOPLEVEL_DECORATION_V1_MODE_SERVER_SIDE;
+	if (toplevel->decoration == nullptr)
+		return false;  /* CSD-only client (e.g. GTK): leave its decorations be */
+	bool client_wants_ssd = toplevel->decoration->requested_mode ==
+			WLR_XDG_TOPLEVEL_DECORATION_V1_MODE_SERVER_SIDE;
 	return wb::negotiate_decoration(toplevel->decorations, client_wants_ssd,
 			kSsdAvailable) == wb::NegotiatedDecoration::ServerSide;
 }

waybox/output.cpp

@@ -233,6 +233,20 @@ void new_output_notify(struct wb_server *server, void *data) {
 			&wlr_scene_tree_create(&server->scene->tree)->node;
 	}
 
+	/* Stack this output's layer trees around the shared toplevel container so
+	 * panels render correctly: background/bottom below ordinary windows; the
+	 * fullscreen, top and overlay layers (where panels like Waybar live) above
+	 * them. New toplevels are children of toplevel_tree, so they never lift
+	 * above the top/overlay layers. */
+	struct wlr_scene_node *tl = &server->toplevel_tree->node;
+	wlr_scene_node_place_below(&output->layers.shell_background->node, tl);
+	wlr_scene_node_place_below(&output->layers.shell_bottom->node, tl);
+	wlr_scene_node_place_above(&output->layers.shell_top->node, tl);
+	wlr_scene_node_place_above(&output->layers.shell_fullscreen->node,
+			&output->layers.shell_top->node);
+	wlr_scene_node_place_above(&output->layers.shell_overlay->node,
+			&output->layers.shell_fullscreen->node);
+
 	wl_list_insert(&server->outputs, &output->link);
 
 	/* Initialise the usable area to the full output; arrange_layers() will

waybox/server.cpp

@@ -129,6 +129,11 @@ bool wb_start_server(struct wb_server* server) {
 	server->scene = wlr_scene_create();
 	server->scene_layout =
 		wlr_scene_attach_output_layout(server->scene, server->output_layout);
+	/* The toplevel container. Created up-front so per-output layer trees (made
+	 * as outputs come up) can be stacked relative to it; toplevels are added as
+	 * its children, so adding/raising a window never lifts it above the panel
+	 * layers. */
+	server->toplevel_tree = wlr_scene_tree_create(&server->scene->tree);
 
 	const char *socket = wl_display_add_socket_auto(server->wl_display);
 	if (!socket) {

waybox/xdg_shell.cpp

@@ -724,11 +724,21 @@ void set_toplevel_fullscreen(struct wb_toplevel *toplevel, bool fullscreen) {
 		struct wlr_output *wlr_output = get_active_output(toplevel);
 		struct wb_output *output = static_cast<struct wb_output *>(
 				wlr_output ? wlr_output->data : NULL);
-		if (output != NULL)
+		if (output != NULL) {
 			toplevel->geometry = output->geometry;  /* layout box: pos + size */
+			/* Lift the window into the fullscreen layer so it covers panels
+			 * (the top layer), which ordinary toplevels sit below. */
+			if (toplevel->scene_tree != NULL)
+				wlr_scene_node_reparent(&toplevel->scene_tree->node,
+						output->layers.shell_fullscreen);
+		}
 		raise_toplevel(toplevel);
 	} else {
 		toplevel->geometry = toplevel->restore_fullscreen;
+		/* Return to the ordinary toplevel container (below the panel layers). */
+		if (toplevel->scene_tree != NULL)
+			wlr_scene_node_reparent(&toplevel->scene_tree->node,
+					toplevel->server->toplevel_tree);
 	}
 
 	wlr_xdg_toplevel_set_fullscreen(toplevel->xdg_toplevel, fullscreen);
@@ -951,7 +961,7 @@ static void handle_new_xdg_toplevel(struct wb_server *server, void *data) {
 	 * decoration nodes). For now the surface sits at the container origin: with
 	 * no decorations the insets are zero, so this is identical to attaching the
 	 * surface directly. */
-	toplevel->scene_tree = wlr_scene_tree_create(&toplevel->server->scene->tree);
+	toplevel->scene_tree = wlr_scene_tree_create(toplevel->server->toplevel_tree);
 	toplevel->surface_tree = wlr_scene_xdg_surface_create(
 		toplevel->scene_tree, xdg_toplevel->base);
 	/* Tag both the container and the surface tree so a click on a decoration