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From: chaffee@reed.UUCP (Alex Chaffee)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Can the Mac actually do animation?
Message-ID: <16310@reed.UUCP>
Date: 9 Apr 91 22:36:49 GMT
References: <6205@cactus.org> <2966@cod.NOSC.MIL> <314@crucible.UUCP> <552@humu.NOSC.Mil> <16301@reed.UUCP>
Organization: Reed College, Portland OR
Lines: 110

Okay, I've gotten enough requests -- here's a repost of Sync.c. Be careful -
I haven't tested this on small Macs.  It's likely that it only works if Color
Quickdraw is installed.

Alex Chaffee
chaffee@reed.bitnet
Reed College, Portland OR 97202
____________________

/*
	Sync.h
*/

/*	Exported Variables	*/

extern	long	vCounter;		/*	just like Ticks - incremented every refresh	*/

/*	Macros/Prototypes	*/

void InstallSync(void);
void RemoveSync(void);
void WaitForSync (void);

static long vblJunk;
#define WaitForSync()	vblJunk = vCounter; do {} while (vblJunk == vCounter);

/*
	Sync.c
	
	Implements a VBL counter (like Ticks) on a Mac II
	
	Usage:
		#include "sync.h"
		InstallSync();
		...
		WaitForSync();
		CopyBits(...);
		...
		RemoveSync();
	
*/

#include "Sync.h"

/*	Types	*/
typedef struct {
	long	goodA5;
	VBLTask	task;
} MYVBLTASK;

/*	Globals	*/

long	vCounter;
static MYVBLTASK	mytask;
static DefVideoRec	video;

/*	Prototypes	*/
static pascal void Task(void);

/*	Task	*/
static pascal void Task(void)
{
	long	oldA5;
	MYVBLTASK	vbltask;
	asm {
		move.l	A5,oldA5	; save off the old value of A5
		move.l	-4(A0), A5	; A0 points to our VBL task record, and earlier we
					; saved CurrentA5 near it
	}
	vCounter++;
	mytask.task.vblCount = 1;	/*	we want to run again real soon	*/
	asm {
		move.l	oldA5,A5
	}
}

/*	InstallSync	*/
void InstallSync(void)
{
	GetVideoDefault(&video);

	mytask.goodA5 = (long)CurrentA5;
	vCounter = 0;

	mytask.task.qType = vType;
	mytask.task.vblAddr = (ProcPtr) Task;
	mytask.task.vblCount = 1;
	mytask.task.vblPhase = 0;
	SlotVInstall(&mytask.task, video.sdSlot);
}

void RemoveSync(void)
{
	SlotVRemove(&mytask.task, video.sdSlot);
}

/*	If you don't want to use the macro, uncomment this function	*/
/*
void WaitForSync (void)
{
	long vJunk = vCounter;
	do {} while ( vCounter == vJunk );
}
*/

-- 
Alex Chaffee
chaffee@reed.bitnet
Reed College, Portland OR 97202
____________________