ViewerAbortDoc.tioga
Copyright Ó 1987 by Xerox Corporation. All rights reserved.
Eric Nickell, January 24, 1987 1:19:09 pm PST
A STANDARD METHOD FOR ABORTING PROCESSES ASSOCIATED WITH VIEWER ACTIONS
CEDAR 7.0 —
ViewerAbort
A standard way to abort processes associated with viewers
Eric Nickell
© Copyright 1986 Xerox Corporation. All rights reserved.
Abstract: ViewerAbort is a client-callable package which lets a user abort (via SHIFT-SWAT or DLion STOP) actions associated with viewers.
Created by: Eric Nickell
Maintained by: Eric Nickell <Nickell.pasa>
Keywords: Viewer, Abort, Stop
XEROX  Xerox Corporation
   Palo Alto Research Center
   3333 Coyote Hill Road
   Palo Alto, California 94304

User
For client packages which utilize ViewerAbort, the user who has started some action in a viewer and then wishes to abort it, holds down the left shift key and the swat key (on a Dorado), or the STOP key (on a DLion) in the viewer associated with the action, to cause the action to stop. Note that it may take up to a half second for ViewerAbort to see this key combination, and even then, there is no guarantee how long it will be until the client package decides to check for an abort.
Clients
For client packages which perform computation-intensive actions which are associated with a viewer, and which would like to permit a user to abort, ViewerAbort may be the answer. The interface consists of a simple procedure to which the client supplies a viewer and a callback procedure. If the user holds down the left shift key and the SWAT key (or just the STOP key on a DLion) in the associated viewer while in the associated viewer the process is executing the call-back procedure, that process will be aborted, which is to say, that if the client chooses to call Process.CheckForAbort, ABORTED will be raised.