// Filename			: Dbuff2.c
// Coded by			: Scott Evans
// Created/Modified	: 16/9/97
// Description		: Demonstrates double buffering using high and low level 
//					  graphics functions

#include <libps.h>

// Header file for yaroze.c, my versions of functions not included
// in Yaroze libraries

#include <yaroze.h>

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

#define SCRNW	320
#define SCRNH	240

// 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;

	// Dither off

	dbp->drawenv.dtd=(dbp+1)->drawenv.dtd=0;
	
	// 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);

	// 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

		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);
}