Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!purdue!mailrus!ncar!tank!nucsrl!bob
From: bob@eecs.nwu.edu (Bob Hablutzel)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Multifinder: how do I patch GetNextEvent?
Message-ID: <10050022@eecs.nwu.edu>
Date: 9 Oct 88 02:31:50 GMT
References: <747@ttrdf.UUCP>
Organization: Northwestern U, Evanston IL, USA
Lines: 27

>   What is the proper way to patch the GetNextEvent() trap for
> compatibility with MultiFinder?.  I have created an INIT that
> patches this call. The first thing that the patch does is call the
> old GetNextEvent, (the one that was there at INIT time.). 
> The purpose of the patch is to translate the CapsLock modifier into
> the command-key modifier.

- symptoms deleted -
 
> Any ideas?

Ideas are easy. Solutions come harder. :-)

The problem here is that you have written a "tail patch". This is a critter
that does it's work _after_ the original ROM routine. These are verboten, since
some of Apple's patches to the OS rely on the return address of the call.
(I'm not kidding, and for more information why, see a recent issue BYTE which 
had a long article on MultiFinder. Yeah, I said BYTE.)

Try this: there is a low memory global called jGNEFilterProc, or something
real close to that. It is called just before _GetNextEvent returns, with A1
pointing to the event record in question. (At least, this is very close to 
the truth - I'm writting this from memory, without documentation).

Bob Hablutzel		BOB@NUACC.ACNS.NWU.EDU
Disclaimer:		I'd never write a practical joke INIT with this 
			information. Nope. Not me.