on-double-click

This method is called when the user double-clicks on a snip in the editor. The clicked-on snip and event records are passed to the method.

• (send a-pasteboard on-double-click snip event) -> void
      snip : snip% object
      event : mouse-event% object

  If snip accepts events, it is designated as the caret owner and all snips in the editor are unselected.