diff -r a0ea718ab1d8 -r 24d9a92fd048 ui/gtk/toolkit.h
--- a/ui/gtk/toolkit.h	Fri Feb 16 18:33:34 2024 +0100
+++ b/ui/gtk/toolkit.h	Fri Feb 16 19:00:53 2024 +0100
@@ -47,9 +47,11 @@
 } UiEventData;
 
 typedef struct UiVarEventData {
-    UiObject   *obj;
-    UiVar     *var;
-    UiObserver **observers;
+    UiObject    *obj;
+    UiVar       *var;
+    UiObserver  **observers;
+    ui_callback callback;
+    void        *userdata;
 } UiVarEventData;