// Filename		: Interlace.c
// Coded by		: Scott Evans
// Created/Modified	: 16/9/97
// Description		: Demonstrates the use of interlace mode

#include <libps.h>

void SetDefDispEnv(DISPENV *,int,int,int,int);
void SetDefDrawEnv(DRAWENV *,int,int,int,int);

// Set r0,g0,b0 members of a structure

#define setRGB0(p,r,g,b)\
	(p)->r0=(r),(p)->g0=(g),(p)->b0=(b)

// Packet buffer and ordering table size

#define NPKTS	1
#define PBSIZE NPKTS*sizeof(GsBOXF)		
#define OT_LENGTH 1			

// To run non-interlace mode comment this define

#define INTERLACE_ON

// Screen size (NTSC)

#ifdef INTERLACE_ON
#define SCRNW	640
#define SCRNH	480
#else
#define SCRNW	320
#define SCRNH	240
#endif

// 2 ordering tables and 2 packet buffers

GsOT mainOT[2],*ot=mainOT;				
GsOT_TAG OTTags[2][1<<OT_LENGTH];
PACKET PacketBuffer[2][PBSIZE],*pb=(PACKET *)PacketBuffer;	

// Double buffer structure

typedef struct
{
	DISPENV dispenv; 	// display environment
	DRAWENV drawenv;	// Drawing environment
	GsOT	*ot;		// Pointer to ordering table
	PACKET *pb;		// Pointer to packet buffer
}DBUFFER;

// 2 double buffers

DBUFFER db[2],*dbp=db;

GsBOXF box;	

void main(void)
{
	// Set ordering table stuff

	ot->length=(ot+1)->length=OT_LENGTH;
	ot->org=OTTags[0];
	(ot+1)->org=OTTags[1];

	// Set drawing area for buffer 0 and 1

	SetDefDrawEnv(&dbp->drawenv,0,0,SCRNW,SCRNH);
	SetDefDrawEnv(&(dbp+1)->drawenv,0,SCRNH,SCRNW,SCRNH);

	// Set display area for buffer 0 and 1

	SetDefDispEnv(&dbp->dispenv,0,SCRNH,SCRNW,SCRNH);
	SetDefDispEnv(&(dbp+1)->dispenv,0,0,SCRNW,SCRNH);

	// Set ordering table for buffer 0 and 1

	dbp->ot=ot;
	(dbp+1)->ot=ot+1;
	
	// Set packet buffer for buffer 0 and 1

	dbp->pb=pb;
	(dbp+1)->pb=pb+PBSIZE;
	
	// Clear background on

	dbp->drawenv.isbg=(dbp+1)->drawenv.isbg=1;
	
	// Background colour=red

	setRGB0(&dbp->drawenv,0x80,0x0,0x0);
	setRGB0(&(dbp+1)->drawenv,0x80,0x0,0x0);

#ifdef INTERLACE_ON
	// Set drawing area for buffer 0 and 1

	SetDefDrawEnv(&dbp->drawenv,0,0,SCRNW,SCRNH);
	SetDefDrawEnv(&(dbp+1)->drawenv,0,0,SCRNW,SCRNH);

	// Set display area for buffer 0 and 1

	SetDefDispEnv(&dbp->dispenv,0,0,SCRNW,SCRNH);
	SetDefDispEnv(&(dbp+1)->dispenv,0,0,SCRNW,SCRNH);

	// Allow drawing in display area

	dbp->drawenv.dfe=0;
	(dbp+1)->drawenv.dfe=0;
#endif

	// Set up a white box

	box.attribute=0;
	box.w=box.h=50;
	box.x=(SCRNW-box.w)>>1;
	box.y=(SCRNH-box.h)>>1;
	box.r=box.g=box.b=0xff;

	// Initialise graphics 

	ResetGraph(0);

	// Turn on display

	SetDispMask(1);

	while(1)
	{
		// Swap buffers

		dbp=(dbp==db ? db+1 : db);

		// Set packet buffer for current buffer

		GsSetWorkBase(dbp->pb);

		// Initialise ordering table

		GsClearOt(0,0,dbp->ot);

		// Put primitive in ordering table

		GsSortBoxFill(&box,dbp->ot,0);

		// Wait for it all to finish

#ifndef INTERLACE_ON
		DrawSync(0);
#endif
		VSync(0);

		// Halt drawing after vertical blank has returned
		// Similar to DrawSync() but does not wait for drawing to 	
		// finish, it just stops the drawing

		ResetGraph(1);

		// Set new drawing and display areas
 
		PutDrawEnv(&dbp->drawenv);
		PutDispEnv(&dbp->dispenv);

		// Execute the primitives in the ordering table
	
		GsDrawOt(dbp->ot);
	}

	exit(0);
}


// Set default drawing environment

void SetDefDrawnEnv(DRAWENV *e,int x,int y,int w,int h)
{
	e->clip.x=x;
	e->clip.y=y;
	e->clip.w=w;
	e->clip.h=h;

	e->tw.x=e->tw.y=tw->w=tw->h=0;

	e->ofs[0]=x;
	e->ofs[1]=y;

	e->tpage-GetTPage(0,0,640,0);

	e->dtd=1;
	e->dfe=1;
	e->isbg=0;

	e->r0=e->g0=e->b0=0;
}

// Set default display environment

void SetDefDispEnv(DISPENV *e,int x,int y,int w,int h)
{
	e->disp.x=x;
	e->disp.y=y;
	e->disp.w=w;
	e->disp.h=h;

	e->screen.x=e->screen.y=0;
	e->screen.w=256;
	e->screen.h=240;

	e->isinter=e->isrgb24=0;
}