code: func (v *Menu) PopupAtWidget(widget IWidget, widgetAnchor gdk.GdkGravity, menuAnchor gdk.GdkGravity, triggerEvent *gdk.Event) {
  	e := (*C.GdkEvent)(unsafe.Pointer(triggerEvent.Native()))
  	C.gtk_menu_popup_at_widget(v.native(), widget.toWidget(), C.GdkGravity(widgetAnchor), C.GdkGravity(menuAnchor), e)
  }
docs: // PopupAtWidget() is a wrapper for gtk_menu_popup_at_widget()