Widget.connectVisibilityNotifyEvent

gulong connectVisibilityNotifyEvent(T)(T callback,  Flag!"After" after =  No.After) if (isCallable!T
    &&  is(ReturnType!T ==  bool)
   && (Parameters!T.length <  1 || (ParameterStorageClassTuple!T[0]  ==  ParameterStorageClass.none &&  is(Parameters!T[0]  ==  gdk.event_visibility.EventVisibility)))
   && (Parameters!T.length <  2 || (ParameterStorageClassTuple!T[1]  ==  ParameterStorageClass.none &&  is(Parameters!T[1] :  gtk.widget.Widget)))
   &&  Parameters!T.length <  3)

Connect to VisibilityNotifyEvent signal.

The ::visibility-notify-event will be emitted when the widget's window is obscured or unobscured.

To receive this signal the #GdkWindow associated to the widget needs to enable the #GDK_VISIBILITY_NOTIFY_MASK mask.

Parameters

`callback`	signal callback delegate or function to connect `bool callback(gdk.event_visibility.EventVisibility event, gtk.widget.Widget widget)` `event` the #GdkEventVisibility which triggered this signal. (optional) `widget` the instance the signal is connected to (optional) `Returns` true to stop other handlers from being invoked for the event. false to propagate the event further.
`after`	Yes.After to execute callback after default handler, No.After to execute before (default)

Returns

Signal ID

Deprecated

Modern composited windowing systems with pervasive

transparency make it impossible to track the visibility of a window reliably, so this signal can not be guaranteed to provide useful information.