gtk:box-child-expand (container child)

container -- a gtk:box container widget
child -- a gtk:widget child widget
expand -- true, if child is to be given extra space

The accessor for the expand child property gets or sets whether the child widget should receive extra space when the parent widget grows. The hexpand or vexpand properties are the preferred way to influence whether the child widget receives extra space, by setting the expand property of the child widget corresponding to the orientation of the box. In contrast to the hexpand property, the expand child property does not cause the box to expand itself.