// Filename			: Dbuff1.c
// Coded by			: Scott Evans
// Created/Modified	: 16/9/97
// Description		: Demonstrates double buffering using high level graphics functions

// Header file for Yaroze library

#include <libps.h>

// The packet buffer must be large enough to store the 
// maximum number of primitives that will be used

// In this program we are only using one primitive a GsBOXF

#define PBSIZE 1*sizeof(GsBOXF)		

// Z resolution of ordering table

#define OT_LENGTH 1			

// Screen width and height (NTSC)

#define SCRNW	320
#define SCRNH	240

// Define 2 ordering tables

GsOT mainOT[2];				
GsOT_TAG OTTags[2][1<<OT_LENGTH];

// Define 2 packet buffers

PACKET PacketBuffer[2][PBSIZE];	

// Define the primitive to be used

GsBOXF box;	
int current_buffer;

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

	mainOT[0].length=mainOT[1].length=OT_LENGTH;
	mainOT[0].org=OTTags[0];
	mainOT[1].org=OTTags[1];

	// Initialise graphics

	ResetGraph(0);

	// Screen width, height, GPU offset etc…

	GsInitGraph(SCRNW,SCRNH,3,0,0);

	// Define display and drawing areas
	// Buffer 0 : Display - 0,0,320,240   Drawing - 0,240,320,240
	// Buffer 1 : Display - 0,240,320,240 Drawing - 0,0,320,240

	GsDefDispBuff(0,0,0,SCRNH);

	// Set up a white box in the centre of the screen

	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;

	// Main loop

	while(1)
	{
		// Find the active buffer (0 or 1)

		current_buffer=GsGetActiveBuff();
		
		// Set the packet buffer for the current buffer

		GsSetWorkBase((PACKET *)PacketBuffer[current_buffer]);

		// Initialise the ordering table

		GsClearOt(0,0,&mainOT[current_buffer]);

		// Put the box primitive into the ordering table

		GsSortBoxFill(&box,&mainOT[current_buffer],0);
		
		// Wait for drawing and vertical blank to finish

		DrawSync(0);
		VSync(0);

		// Swap the buffers
	
		GsSwapDispBuff();

		// Clear the screen in red

		GsSortClear(0x80,0x0,0x0,&mainOT[current_buffer]);

		// Execute the primitives in the ordering table

		GsDrawOt(&mainOT[current_buffer]);	
	}

	exit(0);
}