xwayland: make X11 always-on-top request opt-in

Fixes: #3441

docs/labwc-config.5.scd

@@ -1354,6 +1354,13 @@ situation.
 	*ignoreConfigureRequest* prevents a X11 window to position and size
 	itself.
 
+*<windowRules><windowRule allowAlwaysOnTop="">* [yes|no|default]
+	*allowAlwaysOnTop* allows a X11 window to control its always-on-top
+	state ('above' in X11 terms).
+
+	Note: X11 window always-on-top requests are disallowed by default.
+	This window rule offers a means of allowing it.
+
 *<windowRules><windowRule fixedPosition="">* [yes|no|default]
 	*fixedPosition* disallows interactive move/resize and prevents
 	re-positioning in response to changes in reserved output space, which

include/window-rules.h

@@ -40,6 +40,7 @@ struct window_rule {
 	enum property ignore_configure_request;
 	enum property fixed_position;
 	enum property icon_prefer_client;
+	enum property allow_always_on_top;
 
 	struct wl_list link; /* struct rcxml.window_rules */
 };

src/config/rcxml.c

@@ -300,6 +300,8 @@ fill_window_rule(xmlNode *node)
 			set_property(content, &window_rule->ignore_configure_request);
 		} else if (!strcasecmp(key, "fixedPosition")) {
 			set_property(content, &window_rule->fixed_position);
+		} else if (!strcasecmp(key, "allowAlwaysOnTop")) {
+			set_property(content, &window_rule->allow_always_on_top);
 		}
 	}
 

src/view.c

@@ -1543,6 +1543,9 @@ void
 view_set_layer(struct view *view, enum view_layer layer)
 {
 	assert(view);
+	if (view->layer == layer) {
+		return;
+	}
 	view->layer = layer;
 	wlr_scene_node_reparent(&view->scene_tree->node,
 		view->workspace->view_trees[layer]);

src/window-rules.c

@@ -110,6 +110,10 @@ window_rules_get_property(struct view *view, const char *property)
 					&& !strcasecmp(property, "iconPreferClient")) {
 				return rule->icon_prefer_client;
 			}
+			if (rule->allow_always_on_top
+					&& !strcasecmp(property, "allowAlwaysOnTop")) {
+				return rule->allow_always_on_top;
+			}
 		}
 	}
 	return LAB_PROP_UNSPECIFIED;

src/xwayland.c

@@ -431,6 +431,11 @@ handle_request_above(struct wl_listener *listener, void *data)
 		wl_container_of(listener, xwayland_view, request_above);
 	struct view *view = &xwayland_view->base;
 
+	if (window_rules_get_property(view, "allowAlwaysOnTop") != LAB_PROP_TRUE) {
+		wlr_log(WLR_INFO, "X11 client side always on top request rejected");
+		return;
+	}
+
 	view_set_layer(view, xwayland_view->xwayland_surface->above
 		? VIEW_LAYER_ALWAYS_ON_TOP : VIEW_LAYER_NORMAL);
 }
@@ -727,8 +732,11 @@ handle_map_request(struct wl_listener *listener, void *data)
 		axis |= VIEW_AXIS_VERTICAL;
 	}
 	view_maximize(view, axis);
-	view_set_layer(view, xsurface->above
+
-		? VIEW_LAYER_ALWAYS_ON_TOP : VIEW_LAYER_NORMAL);
+	if (window_rules_get_property(view, "allowAlwaysOnTop") == LAB_PROP_TRUE) {
+		view_set_layer(view, xsurface->above
+			? VIEW_LAYER_ALWAYS_ON_TOP : VIEW_LAYER_NORMAL);
+	}
 	/*
 	 * We could also call set_initial_position() here, but it's not
 	 * really necessary until the view is actually mapped (and at