on-move-to

Called before a snip is moved in the buffer. If the return value is #f, then the move will be aborted. Otherwise, after-move-tois guaranteed to be called after the move has completed.

• (send a-wx:media-pasteboard on-move-to snip x y dragging?) -> boolean
      snip : wx:snip% object
      x : inexact real
      y : inexact real
      dragging? : boolean

  If dragging? is not #f, then this move is a temporary move for dragging.