//-------------------------------------------------------------------
//	vgademo.cpp
//
//	This example demonstrates 256-color PC graphics programming
//	as implemented by IBM's Video Graphics Array (VGA) adapter, 
//	still supported by SVGA devices for backward compatibility.
//
//	programmer: ALLAN CRUSE
//	written on: 08 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()

typedef unsigned char	u8;

u8	*vram = (u8*)0x000A0000;
int	hres = 320, vres = 200;

void set_pixel( int x, int y, int color )
{
	int	posn = y*hres + x;

	vram[ posn ] = color;
}	

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

	for (y = miny; y <= maxy; y++)
		for (x = minx; x <= maxx; x++)
			set_pixel( x, y, color );
}


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



int main( int argc, char **argv )
{
	int	base = (int)vram;
	int	size = (256<<10);
	map_vram( base, size );

	int	minx, midx, maxx, miny, midy, maxy;
	int	x, y, color, radius_squared;

	//----------------------------------------------
	// Demonstrate VGA color graphics (VGA mode 19)
	//----------------------------------------------
	system( "clear ; mode3 19 " );	// 320x200, 256-colors

	// draw screen border
	color = 15;	// white
	minx = 0, maxx = hres-1;
	miny = 0, maxy = vres-1;
	x = y = 0;
	do { set_pixel( x, y, color ); ++x; } while ( x < maxx );
	do { set_pixel( x, y, color ); ++y; } while ( y < maxy );
	do { set_pixel( x, y, color ); --x; } while ( x > minx );
	do { set_pixel( x, y, color ); --y; } while ( y > miny );
	getchar();

	// fill circle (unrescaled)
	midx = hres/2; midy = 23*vres/32; 
	radius_squared = 40*40; color = 6;
	for (y = 4; y <= maxy-4; y++) 
	for (x = 4; x <= maxx-4; x++)
		{
		int	dx = x - midx;
		int	dy = y - midy;
		int	dist_squared = dx*dx + dy*dy;
		color = ( dist_squared < radius_squared ) ? 6 : 150;
		set_pixel( x, y, color );
		}	
	getchar();

	// show the palette of 256-colors
	int	h = 5, v = 5, x0 = 32, y0 = 24;
	for (color = 0; color < 256; color++)
		{
		x = x0 + (color % 32)*8;
		y = y0 + (color / 32)*8;
		fill_rectangle( x, y, h, v, color );
		}	
	getchar();

	system( " mode3 3 " );	// standard 80x25 text mode
}