compositor: add surface role map hook

include/wlr/types/wlr_compositor.h

@@ -97,6 +97,13 @@ struct wlr_surface_role {
 	 * such object exists.
 	 */
 	void (*commit)(struct wlr_surface *surface);
+	/**
+	 * Called when the surface is mapped. May be NULL.
+	 *
+	 * If the role is represented by an object, this is only called if
+	 * such object exists.
+	 */
+	void (*map)(struct wlr_surface *surface);
 	/**
 	 * Called when the surface is unmapped. May be NULL.
 	 *

types/wlr_compositor.c

@@ -828,6 +828,11 @@ void wlr_surface_map(struct wlr_surface *surface) {
 		subsurface_consider_map(subsurface);
 	}
 
+	if (surface->role != NULL && surface->role->map != NULL &&
+			(surface->role_resource != NULL || surface->role->no_object)) {
+		surface->role->map(surface);
+	}
+
 	wl_signal_emit_mutable(&surface->events.map, NULL);
 }