gtk:container-child-property (container child property &optional gtype)

container -- a gtk:container widget
child -- a gtk:widget object which is a child of container
property -- a string with the name of the property to get
gtype -- an optional g:type-t type ID for value
value -- the value of the property

Gets or sets the value of a child property for the child widget of the container. If the gtype type ID is not given, it is determined from the specified property argument.