on [<modes>]window_server [<serial#>] [-|^]<match> { <action> }

This hook is triggered each time a window changes its server association for any reason whatsoever.

The server refnum -2 is special, and it means the window has disconnected; it is no longer associated with any server.

Traditionally, newly created windows will not hook this event, but that might change in the future. Be prepared for forwards compatability. In this case, the old server refnum will be -2.

This first appeared in EPIC5-0.3.2.