ScrollView tasks

[migueldeicaza]

• [ ] should have three modes for showing the scrollbar: never, auto, always
• [ ] should figure out auto-focus, and scroll the view to the right place based on what is focused
• [ ] view.clear() does not work well with contentOffset, as it does not cover the entire region
• [ ] view.redraw() is getting the full size, not the visible size of the ScrollView region affected (so everything has to draw from 0, even if not needed). A child view of say 100x100 inside a 10x10 where contenOffset=30,30 should get a region with (30-30, w:10, h:10) so it can optimize its rendering.
• [ ] Find a way to delegate positionCursor to a child, but if it is out of bounds, snap to bounds. Will likely need positionCursor to be changed, and perhaps return the position, and the caller snap to the boundary.