behavior difference between qscrollview in qt3 and q3scrollview : widget A inside scrollview doesn't grow automatically when the widgets inside A grows

In Qt3 – Insert a Widget A into qscrollview, and put some buttons(B) into a layout in A. If the user changes the text on B, A will grow so that the layout can enlarge B to show the text.
In Qt3Support – A doesn't grow, so B will remain the same size even the text has changed to a longer one.

These two behaviors are different.