//-------------------------------------------------------------------
//	randpats.cpp
//
//	This program uses the standard 'rand()' library-function to
//	generate some pattern-bitmaps and select their colors; then
//	it fills some rectangular screen-areas using these pattern.
//
//	  compile using:  $ g++ randpats.cpp int86.cpp -o randpats 
//
//	programmer: ALLAN CRUSE
//	written on: 15 SEP 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for getchar(), printf() 
#include <stdlib.h>	// for rand() 
#include "int86.h"	// for init8086(), int86()

#define	VRAM_BASE_FOR_VGA 0x000A0000 

typedef unsigned char u8; 

u8 *vram = (u8*)VRAM_BASE_FOR_VGA; 
struct vm86plus_struct	vm; 
int vga_mode = 19, hres = 320, vres = 200;
char	pat[ 8 ];	

int main( int argc, char **argv )
{
	// enter graphics mode
	init8086(); 
	vm.regs.eax = vga_mode;	
	int86( 0x10, vm );	
	
	// draw screen border 
	int	x = 0, y = 0, color = 15; 
	do { vram[ y * hres + x ] = color; ++x; } while ( x < hres-1 ); 
	do { vram[ y * hres + x ] = color; ++y; } while ( y < vres-1 ); 
	do { vram[ y * hres + x ] = color; --x; } while ( x >      0 ); 
	do { vram[ y * hres + x ] = color; --y; } while ( y >      0 ); 
	getchar();

	// setup the subdivisions of the screen to be tiled
	int	wide = hres/2, high = vres/2;
	for (int area = 0; area < 4; area++)
		{
		// create the bitmap for an 8-by-8 2-color pattern
		for (int i = 0; i < 8; i++) pat[ i ] = rand();

		// choose the pattern's foreground/background colors
		int	fgcolor = 32 + rand() % 72;
		int	bgcolor = 104 + rand() % 72;

		// setup coordinates for the area's starting location
		int	x = (area % 2)*wide;
		int	y = (area / 2)*high;
		u8	*dstn = vram + y * hres + x;

		// tile the screen-area with the pattern	
		for (int row = 0; row < high; row++)
			{
			u8	bits = pat[ row % 8 ];
			for (int col = 0; col < wide; col++)
				{
				u8	which = ( bits >>( col % 8 ) )&1;
				int	where = row * hres + col;
				dstn[ where ] = ( which ) ? fgcolor : bgcolor;
				}
			}  
		}
	getchar();
	
	// leave graphics mode 
	vm.regs.eax = 0x0003;	
	int86( 0x10, vm );	
	printf( "\n" );
}