DIRECTORY UndoEvent; UndoEventImpl: CEDAR PROGRAM EXPORTS UndoEvent = BEGIN OPEN UndoEvent; Create: PUBLIC PROC RETURNS [Event] = { RETURN [NEW[EventBody]] }; Note: PUBLIC PROC [event: Event, undoProc: UndoProc, undoRef: REF Change] = { IF event = NIL THEN RETURN; event.subevents _ NEW[SubEventBody _ [event.subevents,undoProc,undoRef]] }; Undo: PUBLIC PROC [undoEvent: Event, currentEvent: Event _ NIL] = { sub: SubEvent; IF undoEvent=NIL THEN RETURN; sub _ undoEvent.subevents; undoEvent.subevents _ NIL; UNTIL sub=NIL DO sub.undoProc[sub.undoRef,currentEvent]; sub _ sub.next; ENDLOOP }; Reset: PUBLIC PROC [event: Event] = { IF event # NIL THEN event.subevents _ NIL }; Empty: PUBLIC PROC [event: Event] RETURNS [BOOL] = { RETURN [event=NIL OR event.subevents=NIL] }; END. BUndoEventImpl.mesa Copyright Σ 1985, 1986, 1988 by Xerox Corporation. All rights reserved. written by Bill Paxton, June 1981 last edit by Bill Paxton, April 5, 1982 12:38 pm Doug Wyatt, February 17, 1988 3:55:20 pm PST calls undoProc[undoRef] for each subevent in reverse order that subevents originally happened Κ’˜codešœ™KšœH™HKšœ!™!Kšœ1™1K™,—K˜šΟk ˜ K˜ —K˜KšΠbl œœœ˜Kšœ ˜Kšœœ ˜K˜Kš Οnœœœœ œœ˜BK˜šŸœœœ-œ ˜MKšœ œœœ˜šœœ˜$K˜&K˜——šŸœœœ*œ˜CKšœ*™*Kšœ3™3K˜Kšœ œœœ˜Kšœ1œ˜5Kšœœœ9œ˜SK˜—KšŸœœœœ œœœ˜RK˜KšŸœœœœœœœœœ˜aK˜Kšœ˜—…—θ