setChildIndex method
Sets the index of a child in the list of children of this container.
Implementation
void setChildIndex(GDisplayObject child, int index) {
final old = getChildIndex(child);
if (old == index) return;
if (old == -1) {
throw ArgumentError.value(child, null, 'Not a child of this container');
}
children.removeAt(old);
children.insert(index.clamp(0, numChildren), child);
requiresRedraw();
}