get-visible-position-range

Returns the range of positions which are currently visible to the user.

The result is only valid when the editor is displayed (see Basic Organization). Calling this method may force the recalculation of location information, even if the editor currently has delayed refreshing (see refresh-delayed?).

• (send a-text get-visible-position-range start end) -> void
      start : boxed exact non-negative integer or #f
      end : boxed exact non-negative integer or #f

  The start box is filled with first position visible to the user, unless start is #f. The end box is filled with last position visible to the user, unless end is #f.