child_type() returns an integer describing the type of child the container is expecting to be packed into it. This is mostly for internal use, but could perhaps be useful for diagnosis.

The return values are as follows from most containers:

GTK_TYPE_NONE = 1 (generated where no widget can be added, e.g. by a descendant of GtkBin already containing a child, or a GtkPaned already containing both children, or a GtkOptionMenu)

GTK_TYPE_WIDGET = 39701 (generated where non-specific widgets may be added, e.g. by GtkBox descendants, GtkNotebook, GtkFixed, GtkPacker or GtkTable)

The exceptions are GTK_TYPE_LIST_ITEM, GTK_MENU_ITEM and GTK_TREE_ITEM, all of which can be any of a variety of widget types depending on how the items are produced.