Child Type

The child_type method returns the type of children a container can hold. For example, a GtkMenuShell (parent class of GtkMenu and GtkMenuBar) can only hold children of type GTK_TYPE_MENU_ITEM. The child_type method allows GUI builders and scripting languages to determine at runtime what sort of children a container will accept. GTK_TYPE_NONE indicates that a container will not accept children at this time, for whatever reason.

The GtkBin implementation accepts GTK_TYPE_WIDGET if the bin is empty, and GTK_TYPE_NONE if the bin already contains a child:

static GtkType
gtk_bin_child_type (GtkContainer *container)
{
  if (!GTK_BIN (container)->child)
    return GTK_TYPE_WIDGET;
  else
    return GTK_TYPE_NONE;
}