widget should be mapped along with its when its parent
is mapped and widget has been shown with gtkWidgetShow. gtkWidgetSetChildVisible(object, is.visible)objectis.visibleTRUE, widget should be mapped along with its parent.gtkWidgetSetParent, to avoid mapping
children unnecessary before immediately unmapping them. However
it will be reset to its default state of TRUE when the widget
is removed from a container.
Note that changing the child visibility of a widget does not
queue a resize on the widget. Most of the time, the size of
a widget is computed from all visible children, whether or
not they are mapped. If this is not the case, the container
can queue a resize itself.
This function is only useful for container implementations and
never should be called by an application.