//-------------------------------------------------------------------
//	animate1.cpp
//
//	This program shows how to synchronize vram updates with the
//	CRT's Vertical Retrace signal, so that drawing occurs while 
//	the screen is blanked, thus allowing for smooth animations.
//	It's an initial prototype for implementing the "pong" game.
//
//	programmer: ALLAN CRUSE
//	date begun: 21 AUG 2003
//	completion: 17 SEP 2003
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for close() 
#include <sys/mman.h>	// for mman() 
#include <sys/io.h>  	// for iopl(), inb() 

#define VRAM_BASE 0xB0000000
#define VRAM_SIZE (1 << 20)

typedef unsigned char	PEL;

PEL *fb = (PEL*)VRAM_BASE;
int display_mode = 0x4101;
int hres = 640, vres = 480;
char devname[] = "/dev/vram";

void vsync( void )
{
	// wait for current retrace to finish
	while ( ( inb( 0x3DA ) & 8 ) != 8 );
	// then wait till next retrace begins
	while ( ( inb( 0x3DA ) & 8 ) == 8 );
}

void draw_rectangle( int x, int y, int h, int v, int color )
{
	int	minx = x, miny = y, maxx = x+h-1, maxy = y+v-1;

	do { fb[ y*hres + x ] = color; ++x; } while ( x < maxx );	
	do { fb[ y*hres + x ] = color; ++y; } while ( y < maxy );	
	do { fb[ y*hres + x ] = color; --x; } while ( x > minx );	
	do { fb[ y*hres + x ] = color; --y; } while ( y > miny );	
}	

void fill_rectangle( int x, int y, int h, int v, int color )
{
	int	minx = x, miny = y, maxx = x+h-1, maxy = y+v-1;

	for (y = miny; y <= maxy; y++)
		for (x = minx; x < maxx; x++)
			fb[ y*hres + x ] = color;
}


void fill_oval( int x, int y, int h, int v, int color )
{
	int	midh = (h+1)/2, midv = (v+1)/2;
	
	for (int r = 0; r < v; r++)
		for (int k = 0; k < h; k++)
			{
			int	dh = k - midh;
			int	dv = r - midv;
			int	rr = midh * midv;
			dh *= midv;
			dv *= midh;
			if ( dh*dh + dv*dv < rr*rr )
				fb[ (y+r)*hres + (x+k) ] = color;
			}
}


void map_system_memory( int base, int size )
{
	int	prot = PROT_READ | PROT_WRITE;
	int	flag = MAP_FIXED | MAP_SHARED;
	void	*mm = (void*)base;
	int	fd = open( devname, O_RDWR );
	if ( fd < 0 ) { perror( devname ); exit(1); }
	if ( mmap( mm, size, prot, flag, fd, 0 ) == MAP_FAILED )
		{ perror( "mmap" ); exit(1); }
	close( fd );
}


int main( int argc, char **argv )
{
	int	speed = 2;	// set the default speed

	// allow the user to specify an alternative speed
	if ( argc > 1 ) 
		{ 
		int 	arg = atoi( argv[1] );
		if (( arg > 0 )&( arg < 10 )) speed = arg; 
		} 

	// install SVGA device-driver and map in the VRAM 
	system( "/sbin/insmod vram.o" );
	map_system_memory( VRAM_BASE, VRAM_SIZE );

	// allow i/o (for detecting CRT vertical retrace)
	if ( iopl( 3 ) ) { perror( "iopl" ); exit(1); }

	// enter graphics mode
	char	command[ 40 ];
	sprintf( command, "clear ; mode3 %d ", 0x4101 );
	system( command );	// 640x480, 256-color, w/LFB

	// draw screen border	
	int	black = 0, white = 15, blue = 9, green = 10, yellow = 14;
	int	x = 0, y = 0, wide = hres, high = vres;
	draw_rectangle( x, y, wide, high, white );
	getchar();
	// draw game wall
	x += 40, y += 30, wide -= 80, high -= 60;
	fill_rectangle( x, y, wide, high, blue );
       	x += 20, y += 20, wide -= 40, high -= 40;
	fill_rectangle( x, y, wide, high, black );	
	getchar();
	// draw game ball
	int	xpos = 100, ypos = 200, diam = 20;
	fill_oval( xpos, ypos, diam, diam, yellow );
	getchar();
	// draw game paddle
	fill_rectangle( 80, 454, 100, 8, green );
	getchar();

	// animate the game ball
	int	minx = x, maxx = x+wide-diam, dx =  1;
	int	miny = y, maxy = y+high-diam, dy = -1;
	int	incs, xold, yold;
	int	hits = 5;
	do	{
		xold = xpos;
		yold = ypos;
		for (int incs = 0; incs < speed; incs++)
			{
			xpos += dx;
			ypos += dy;
			if (( xpos <= minx )||( xpos >= maxx )) dx = -dx;
			if (( ypos <= miny )||( ypos >= maxy )) dy = -dy;
			if ( ypos >= maxy ) --hits;
			}
		vsync();
		fill_oval( xold, yold, diam, diam, black );
		fill_oval( xpos, ypos, diam, diam, yellow );
		}
	while ( hits > 0 );

	// leave graphics mode
	system( "mode3 3" );
}