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From: jwhitnel@csib.UUCP
Newsgroups: comp.sys.mac
Subject: Re: article about jGNEFilter in MacTuto
Message-ID: <1172@csib.UUCP>
Date: Fri, 14-Aug-87 12:43:46 EDT
Article-I.D.: csib.1172
Posted: Fri Aug 14 12:43:46 1987
Date-Received: Thu, 20-Aug-87 01:30:00 EDT
References: <164500042@uiucdcsb> <164500043@uiucdcsb>
Reply-To: jwhitnel@csib.UUCP (Jerry Whitnell)
Organization: Communications Solutions Inc., San Jose, Ca
Lines: 61

In article <164500043@uiucdcsb> kkim@uiucdcsb.cs.uiuc.edu writes:
| therefore, if i can modify keydown events within a desk acc without patching
|GetNextEvent, i will be happy to hear the method.  if i have to patch, i 
|would like to know how to patch it (probably using these two traps).

I'm writting this without reference to IM, so take it with a small grain of
salt.  This is in C, translation to Pascal or other lanaguages is left as
an exercise for the reader.

#define GNE_TRAP 0xa??? /* Trap number for GetNextEvent (from IM) */

typedef int (*funcptr)();    /* Pointer to function returning an int */

functptr oldGetNextEvent;

/* initlization code */
    oldGetNextEvent = NGetTrapAddr( GNE_TRAP );
    NSetTrapAddr( myGetNextEvent );

/* This is the patch itself, parameters must match GetNextEvent */
pascal Boolean myGetNextEvent( event, mask )
EventRecord *event;
int mask; {
    Boolean retCode;

    /* First call real GetNextEvent to get the event.  CallPascalW calls
    ** indirectly a pascal function from C.  Your glue may differ here
    */
    retCode = CallPascalW( event, mask, oldGetNextEvent );
    if ( retCode )
    {
	/* We have an event, so preprocess it */
    }

    return( retCode );
}

/* termination code.  Must be executed before application termination or
** bad things will happen, not the least of which is your mac will crash
*/
     SetTrapAddr( GNE_TRAP, oldGetNextEvent );


That's it.  The initilzation code is executed once when your DA initlizes,
the termination code is executed once when your DA is closed and the patch
code is what is executed when the application calls GetNextEvent.  Caveat,
this method works only on Mac+ or newer system, it will not work on 64K ROM
systems (and no flames about that, please).

    
|
| thanks.
|
|Kyongsok KIM
|arpanet/csnet: kkim@a.cs.uiuc.edu
|usenet/uucp  : {seismo, pur-ee, ihnp4}!uiucdcs!kkim


Jerry Whitnell                           It's a damn poor mind that can only
Communication Solutions, Inc.            think of one way to spell a word.
						-- Andrew Jackson