Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!midway!gargoyle!ddsw1!obdient!gagme!essam
From: essam@gagme.chi.il.us (Essam Khairullah)
Newsgroups: comp.sys.mac.programmer
Subject: Need jGNEFilter help
Message-ID: <917@gagme.chi.il.us>
Date: 28 Nov 90 06:43:52 GMT
Distribution: na
Organization: GAGME Public Access UNIX, Chicago, Illinois, USA
Lines: 80

I'm writing an INIT that patches GetNextEvent to show the user an alert
at a specified time.  Unfortunately, it causes problems.  For instance, if
I'm in the Finder and I activate my screen saver and then deactivate it, my
patch doesn't notify the Finder to redraw its screen.

I called Symantec (I'm using THINK C 4.0) and they suggested I try using
the low-memory global jGNEFilter instead of actually patching GNE.

I must be doing something wrong, because now even worse problems occur
than when I just patched GNE itself.  In the original INIT, I patched
SystemTask and it worked just fine, but I allocate memory and SystemTask
is marked as not moving memory, so I figured it would be safer to patch
something that is allowed to move memory.

Here's a sample of the code I'm using:

void	main( void)
{
ProcPtr		oldJGNEFilter;
Handle		myHandle;

/* Get handle to my routine... */
asm
	{
	move.L A0, myPtr;
	}
RememberA0();
SetUpA4();	/* Allow use of global variables */
myHandle = RecoverHandle( myPtr);
DetachResource( myHandle);

.....	/* Allocate and initialize global data */

oldJGNEFilter = JGNEFilter;	/* Save original JGNEFilter value */
JGNEFilter = ( ProcPtr) newJGNEFilter;	/* Install my own filter  */
RestoreA4();
}

pascal	void	newJGNEFilter ( void)                                         
{
long	saveD0, saveD1, saveA1, saveA7;

asm		/* Save certain registers used by JGNEFilter */
	{
	move.L D0, saveD0;
	move.L D1, saveD1;
	move.L A1, saveA1;
	move.L A7, saveA7;
	}
SetUpA4();	/* Allow use of global variables */

.....	/* Check if it's time to call my routine, call it if neccessary */

asm		/* Restore saved registers */
	{
	move.L saveD0, D0;
	move.L saveD1, D1;
	move.L saveA1, A1;
	move.L saveA7, A7;
	}
oldJGNEFilter;	/* Call original JGNEFilter */
RestoreA4();	/* Clean things up and return */
}

And that's it!  I hope that I'm just doing something stupid and obvious
so it's easily fixed.  Like I said, it worked just fine when I was patching
SystemTask, but I wanted to be safe.  BTW, if I call NewDialog and give
it storage for the DialogRecord and also provide a handle of the itemList,
does it allocate memory, and if so, can I do something to avoid it?  If
it's not too much trouble, I may just keep on patching SystemTask if I can
do it without allocating memory.

Anyhow, thanks in advance for any help anyone can offer.


-- 

Essam Khairullah					essam@gagme.chi.il.us

I don't got no fancy signature.