//-------------------------------------------------------------------
//	brickpat.cpp
//
//	This program uses an 8-by-8 pattern-glyph to fill the screen
//	with a red-and-white brick-wall pattern.  It executes in VGA
//	graphics mode 19 (320-by-200, 256-colors).  Can you adapt it
//	to execute in a 16-color graphics mode (e.g., VGA mode 18)?
//
//	  compile using:  g++ brickpat.cpp int86.cpp -o brickpat
//
//	programmer: ALLAN CRUSE
//	written on: 13 SEP 2003
//	revised on: 04 SEP 2005  -- replaced svgalib with 'int86()'
//-------------------------------------------------------------------

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

#define VRAM_BASE_FOR_VGA  0x000A0000

unsigned char	*vram = (unsigned char *)VRAM_BASE_FOR_VGA;
struct vm86plus_struct	vm;
int vga_mode = 19, hres = 320, vres = 200;

char brickpat[ 8 ] = { 0xFF, 0x80, 0x80, 0x80, 0xFF, 0x08, 0x08, 0x08 };

void tile_area( int x, int y, int h, int v, int fg, int bg, char *pat );

int main( int argc, char **argv )
{
	// setup 1-MB memory-map and I/O permission for BIOS routines
	printf( "\e[H\n" );		// avoid getchar jerk
	init8086();			// allows BIOS access

	// enter graphics mode
	vm.regs.eax = vga_mode;
	int86( 0x10, vm );

	// draw white screen border
	int	minx = 0, maxx = hres-1, miny = 0, maxy = vres-1;
	int	x = 0, y = 0, color = 15;
	do { vram[ y*hres + x ] = color; ++x; } while ( x < maxx );	
	do { vram[ y*hres + x ] = color; ++y; } while ( y < maxy );	
	do { vram[ y*hres + x ] = color; --x; } while ( x > minx );	
	do { vram[ y*hres + x ] = color; --y; } while ( y > miny );	
	getchar();
	
	// fill a screen region with our 2-color brick pattern
	int	red = 4, white = 15;
	tile_area( 1, 1, hres-2, vres-2, white, red, brickpat );
	getchar();

	// restore standard text mode
	vm.regs.eax = 0x0003;
	int86( 0x10, vm );
	printf( "\n" );
}



void tile_area( int x, int y, int h, int v, int fg, int bg, char *pat )
{
	int	minx = x, maxx = x+h-1, miny = y, maxy = y+v-1;
	
	for (y = miny; y <= maxy; y++)
	for (x = minx; x <= maxx; x++)
		{
		int	r = y % 8;	
		int	k = x % 8;
		int	color = ( pat[ r ] & (0x80>>k) ) ? fg : bg;
		vram[ y*hres + x ] = color;
		}
}