can-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 on-select and after-select.

The editor is internally locked for writing when this method is called (see also Locks).

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

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