Unhide the un-pressed button layer. Mouse events for left scrollbar button. Unhide the un-pressed button layer. Mouse events for up scrollbar button. Unhide the un-pressed button layer.
Mouse events for down scrollbar button.
Unhide the un-pressed button layer. Mouse events for horizontal scrollbar stub. If we are, calculate the new position, and update the clip. Mouse events for vertical scrollbar stub. If we are, calculate the new position, and update the clip.