Accessor of the slot visible of the gtk-widget class.
The generic function gtk-widget-visible determines whether the widget is visible. Note that this does not take into account whether the widget's parent is also visible or the widget is obscured in any way.
The generic function (setf gtk-widget-visible) sets the visibility state of widget.
This function simply calls the functions gtk-widget-show or gtk-widget-hide but is nicer to use when the visibility of the widget depends on some condition.