Reimplemented from QLayoutItem. Returns the index of w, or -1 if w is not found. Reimplemented from QLayoutItem. Inserts item in this box layout at index index. If index is negative, the item is added at the end.
Inserts layout at index index, with serial stretch factor stretch.
If index is negative, the layout is added at the end. Inserts a non-stretchable space at index index with size size. If index is negative, the space is added at the end. QBoxLayout gives default border and spacing. This function adds additional space.