code: func goTickCallbacks (widget *C.GtkWidget, frameClock *C.GdkFrameClock, userData C.gpointer) C.gboolean {
  	id := int(uintptr(userData))
  
  	tickCallbackRegistry.Lock()
  	r := tickCallbackRegistry.m[id]
  	tickCallbackRegistry.Unlock()
  
  	return gbool(r.fn(
  		wrapWidget(glib.Take(unsafe.Pointer(widget))), 
  		gdk.WrapFrameClock(unsafe.Pointer(frameClock)),
  		r.userData,
  	))
  }
docs: //export goTickCallbacks