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From: cmcclary@bronze.ucs.indiana.edu (Charles McClary)
Newsgroups: comp.sys.mac.programmer
Subject: Struggling with jGNEFilter
Message-ID: <1991Jan22.160544.24382@bronze.ucs.indiana.edu>
Date: 22 Jan 91 16:05:44 GMT
Sender: news@bronze.ucs.indiana.edu (USENET News System)
Organization: Indiana Univeristy
Lines: 75

I am struggling  with setting a procedure to jGNEFilter.  I have a feeling 
I need to add assembly somewhere (setting the jGNEFilter are, I think).  
Can this be done in C?  I have included my source for reference.
Thanks,
Charles McClary
cmcclary@bronze.ucs.indiana.edu

/**********  SOURCE  **********/
/********** Attach procedure to jGNEFilter ***********/

#include <SetUpA4.h>

#defineNIL_POINTER0L

ProcPtr     oldjGNEFilter;
Str255     trash;

pascal void NewjGNEFilter(void);
void ResetFlags(void);
void main(void);

pascal void NewjGNEFilter()
{
     SetUpA4();

     asm 
     {
          move.l oldjGNEFilter,A1;     /* save the global in register a1 */
     } 

     RestoreA4();

     asm 
     {
          unlk A6;          /* remove the stack frame */
          jmp (A1);      /* jump to the old SystemEvent */
     }
}

/**********  main  **********/
void main()
{
     Handle     myHandle = NIL_POINTER;
     Ptr          myPtr;
     SysEnvRec     world;
     Str255          *namePtr;

     asm
     {
          move.l A0, myPtr     /*  copy address of this program to myPtr  
*/
     }

     RememberA0();
     SetUpA4();

     if (!Button())
     {
          myHandle = RecoverHandle(myPtr);
          DetachResource(myHandle);

          oldjGNEFilter = JGNEFilter;   
         JGNEFilter = (ProcPtr) NewjGNEFilter;

          SysBeep(1);
     }

     RestoreA4();
}

Charles McClary
Workstations Division
University Computing Services
Indiana University
cmcclary@bronze.ucs.indiana.edu