Set the number of lines the window contains: the derived class must
provide the heights for all lines with indices up to the one given here
in its \helpref{OnGetLineHeight()}{wxvscrolledwindowongetlineheight}.
Set the number of lines the window contains: the derived class must
provide the heights for all lines with indices up to the one given here
in its \helpref{OnGetLineHeight()}{wxvscrolledwindowongetlineheight}.