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From: jmunkki@hila.hut.fi (Juri Munkki)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Mac II retrace manager and Tick Counts
Message-ID: <1990Sep12.132724.17570@santra.uucp>
Date: 12 Sep 90 13:27:24 GMT
References: <24126@dartvax.Dartmouth.EDU> <1990Sep12.064502.16870@cs.uow.edu.au>
Sender: news@santra.uucp (Cnews - USENET news system)
Reply-To: jmunkki@hila.hut.fi (Juri Munkki)
Organization: Helsinki University of Technology, FINLAND
Lines: 121

In article <1990Sep12.064502.16870@cs.uow.edu.au> stephen@cs.uow.edu.au (The Mighty Ogbo) writes:
>thomas@eleazar.dartmouth.edu (Thomas Summerall) writes:
>
>>	[Old way deleted]
>
>>Is there anyway to simulate this on the Mac II?  Does the apple video card
>>generate a tick of some kind?  I just don't have enough experience to know what
>>I can and can't do in an interrupt driven SlotVInstall routine, and I don't
>>want to find out by trial and error if I don't have to...
>
>Have a look in one of the latest MacTutors. It shows how to set up a SlotV
>routine, with full Pascal code - easily translated to C if you need - and
>the actual call where you use it in the main program is actually quite
>simple.

Here's something I wrote for the Sega 3D glasses. I have edited out some
parts of it and it only installs a vbl task for the main display. The code
is in Think C and depends on the inline assembler, so it might not be easy
to port to other compilers.

#include <VRetraceMgr.h>

typedef	struct
{
	int	theslot;	/*  Slot number			*/
	int	ticker;		/*  A counter			*/
	int	called;		/*  A flag			*/
	VBLTask	VBL;		/*  VBLTask entry		*/
	long	RealA5;		/*  A5 saved here.		*/
}	VVars;

/*
>>	If A5 points to a VVars structure, the following macro will become
>>	xx(A5), where xx is the offset into that structure element.
*/
#define VBV(field)		((int) &((VVars *) 0)->field)(A5)

/*
>>	SetUpVBLTask contains and sets up a VBL task that
>>	acts as a clock and sets a flag every time through.
>>	It also calls a dirty blitter routine if a flag is
>>	set. Calling the dirty blitter should be an option,
>>	since it might crash any time...
*/
void	SetUpVBLTask()
{
	GDHandle	MainDisplay;
	AuxDCEHandle	DisplayDriver;
	SysEnvRec	theWorld;
	
	long	vbltask;

	asm {
	lea	@myvbltask,A0	;	Get address of vbltask
	move.l	A0,vbltask	;	Store in local variable
	lea	@mybase,A0	;	Get addr of variable base storage
	lea	Vv,A1		;	Get addr of Vv record
	move.l	A1,(A0)		;	Store base in base storage
	move.l	A5,Vv.RealA5
	}

	SysEnvirons(1,&theWorld);	/*  Where are we running?	*/

	Vv.VBL.qType=vType;		/*  Vertical blanking queue.	*/
	Vv.VBL.vblAddr=(ProcPtr)vbltask;/*  Address of task		*/
	Vv.VBL.vblCount=1;		/*  Every tick			*/
	Vv.VBL.vblPhase=0;		/*  0 is ok..			*/

	if(theWorld.hasColorQD)		/*  Possibly more than one monitor?*/
	{	MainDisplay=GetMainDevice();
			/*	Can't handle more than one...		*/
		DisplayDriver=(void *)GetDCtlEntry((*MainDisplay)->gdRefNum);
		Vv.theslot=(*DisplayDriver)->dCtlSlot;
		SlotVInstall(&Vv.VBL,Vv.theslot);
			/*	Use main display VBL queue.		*/
	}
	else
	{	VInstall(&Vv.VBL);	/*  Install task in queue	*/
	}
	return;
	
/*
>>	This is the actual VBL task that gets executed.
>>	It just increments a counter and sets a flag
>>	every time it's called.
*/
asm	{
@myvbltask
	move.l	A5,-(SP)	;	Save A5
	move.l	@mybase,A5	;	Get Vv address into A5
	move.w	#1,VBV(VBL.vblCount)	;	Call again.
	move.w	#1,VBV(called)	;	Flag screen blank
	add.w	#1,VBV(ticker)	;	add one to counter
	
	move.l	(sp)+,A5
	rts
@mybase
	dc.l	0		;	Vv record address stored here.

	}
}

If you need to call one of your own routines that needs access to global
variables, put it before you restore A5 and add the following line before
it:
	move.l	VBV(RealA5),A5

Before you quit the application, you should call the following routine
to remove the VBL task:

	if(theWorld.hasColorQD)
		SlotVRemove(&Vv.VBL,Vv.theslot);
	else
		VRemove(&Vv.VBL);

I hope I remembered to include all the necessary parts.

   ____________________________________________________________________________
  / Juri Munkki	    /  Helsinki University of Technology   /  Wind  / Project /
 / jmunkki@hut.fi  /  Computing Center Macintosh Support  /  Surf  /  STORM  /
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