Gets the position of a #GNode with respect to its siblings. @child must be a child of @node. The first child is numbered 0, the second 1, and so on.
a child of @node
the position of @child with respect to its siblings
See Implementation
Gets the position of a #GNode with respect to its siblings. @child must be a child of @node. The first child is numbered 0, the second 1, and so on.