If the id is not specified, set it blank. Update the clipping. If we're two big, we don't need scroll buttons either. Otherwise, we do need scrollbar stubs and buttons. Repeat the above clipping and scrollbar steps for the vertical scrollbar.
Mouse events for anywhere on the window.
Mouse events for right scrollbar button. Unhide the un-pressed button layer. Mouse events for left scrollbar button. Unhide the un-pressed button layer. Mouse events for up scrollbar button.