/*! Validate client, by making sure no Destroy or Unmap events exist in
the event queue for the window.
@return true if the client is valid; false if the client has already
been unmapped/destroyed, and so is invalid.
*/
/*! Validate client, by making sure no Destroy or Unmap events exist in
the event queue for the window.
@return true if the client is valid; false if the client has already
been unmapped/destroyed, and so is invalid.
*/