The Face Object Field Actors on scroll

on-scroll is invoked when a scrollbar is asked to scroll the face this actor belongs to. This actor should exist if you want to attach a SCROLLER style to this style.

The argument is the scroller face.

The actor returns TRUE, if the face was scrolled.

Do not confuse this with on-scroll-event, which is for receiving scroll events from the mouse wheel.

Examples

Scroll a text area face:

on-scroll: [ ; arg: scroller
  gob: sub-gob? face
  
  ; subtract view area size from total text size:
  size: negate max 0x0 gob/size - face/gob/size
  
  ; multiply by scroll amount:
  offset: size * arg/state/value
  
  ; change only the axis
  axis: face-axis? arg
  xy: gob/offset
  xy/:axis: offset/:axis
  gob/offset: xy
  
  show-later face
  
  true ; we got it
]