#vscroll off vertically scrolls by off. A negative offset moves up, a positive one moves down. Checks are performed not to scroll out of bounds.

#hscroll off horizontally scrolls by off. A negative offset moves left, a positive one moves right. Checks are performed not to scroll out of bounds.

#offsets return x-offset and y-offset, i.e. the top left corner coordinates displayed of the child content.

#scroll_to ~x ~y sets x-offset and y-offset to x and y. x and y are corrected to valid bounds (> 0 and < content - displayed rect).

#hscroll_range returns the start and stop horizontal range (from 0. to 1.) of the child which is currently displayed.

#vscroll_range returns the start and stop vertical range (from 0. to 1.) of the child which is currently displayed.