on-select

This method is called before a snip in the pasteboard is selected or deselected. If #f is returned, the selection change is disallowed. See also after-select.

• (send a-wx:media-pasteboard on-select snip on?) -> boolean
      snip : wx:snip% object
      on? : boolean

  If on? is #t, then snip will be selected, otherwise snip will be deselected.