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From: dlyons@Apple.COM (David A. Lyons)
Newsgroups: comp.sys.apple2
Subject: Re: SetVector and Keyboard Interrupts
Keywords: SetVector, Keyboard Interrupts
Message-ID: <42638@apple.Apple.COM>
Date: 4 Jul 90 22:50:36 GMT
References: <266201eb.2a84@petunia.CalPoly.EDU> <42395@apple.Apple.COM> <1415@madnix.UUCP>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 28

In article <1415@madnix.UUCP> jason@madnix.UUCP (Jason Blochowiak) writes:
>In article <42395@apple.Apple.COM> dlyons@Apple.COM (David A. Lyons) writes:
>> [...] but I can think of at least one hacky way:  patch
>>SetVector to check for vector number $000f, handle all the others by passing
>>control to the Real SetVector code, and handle $f by keeping the passed
>>handler for your own use & giving YOUR address to the real SetVector.  When
>>your handler is called, you can call the Real vector if you don't want the
>>keypress.
>
>Oooh, ick! Then wouldn't it also be necessary to watch for EMStartUp &
>EMShutDown calls, so that any app that relied on the vector patches being
>purged on EMShutDown wouldn't cause a post-run crash?

I don't see the difficulty--EMShutDown call SetVector to restore the
keyboard interrupt vector to its pre-EMStartUp value.  (I suppose you would
also have to patch GetVector to return the "real" value instead of the
patch.)

This approach works with keyboard interrupts (as enabled and disabled with
IntSource) whether or not the event manager is used.
-- 
David A. Lyons, Apple Computer, Inc.      |   DAL Systems
Apple II Developer Technical Support      |   P.O. Box 875
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