void gtk_widget_set_child_visible ( GtkWidget* widget, gboolean is_visible )
widget should be mapped along with its when its parent
is mapped and
widget has been shown with gtk_widget_show().
The child visibility can be set for widget before it is added to
a container with gtk_widget_set_parent(), 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.