Path: utzoo!mnetor!uunet!husc6!m2c!applix!scott
From: scott@applix.UUCP (Scott Evernden)
Newsgroups: comp.sys.amiga
Subject: Re: LVOs and SetFunction
Message-ID: <677@applix.UUCP>
Date: 20 Mar 88 02:32:26 GMT
References: <8803060000.AA29981@cory.Berkeley.EDU> <661@applix.UUCP> <1581@sugar.UUCP>
Reply-To: scott@applix.UUCP (Scott Evernden)
Organization: APPLiX Inc., Westboro MA
Lines: 39

In article <1581@sugar.UUCP> schaub@sugar.UUCP (Markus Schaub) writes:
>In article <661@applix.UUCP>, scott@applix.UUCP (Scott Evernden) writes:
>>
>> VOID myScrollRaster();
>> 
>>     oldScrollRaster = SetFunction(GfxBase, (long) lvoScrollRaster,
>>                                     myScrollRaster);
>> -scott
>
>How do you access the parameters of ScrollRaster? My magic book tells me
>that there are 7 parameters available in 7 registers.

This SetFunction() call allows me to *intercept* calls to ScrollRaster().
The parameters are in the registers they're supposed to be in.  Perhaps I
don't follow the question?  Here's an sketch of some code continuing
the example above (again, for Manx C):

#asm
	public	_geta4
	public	_myScrollRaster

_myScrollRaster:		; 'scuse me
	move.l	a4,-(sp)
	jsr	_geta4		; establish addressing

	tst.l	do_i_need_to_intercept_scroll_raster
	beq.s	1$

	movem.l	a1/d0-d5,-(sp)		; save args passed to ScrollRaster()
	jsr	_do_my_scroll_raster_thing	; perhaps accessing parms
	movem.l	(sp)+,a1/d0-d5		; restore passed parameters

1$:	movea.l	_oldScrollRaster,a0	; the real vector
	movea.l	(sp)+,a4		; a4 as it was
	jmp	(a0)			; go do the real thing

#endasm

-scott