//-------------------------------------------------------------------
//	drawtext.cpp
//
//	This program shows how a graphics application can draw text,
//	based on a character glyph-table stored in the VGA firmware.   
//	
//	compile using:	g++ drawtext.cpp lrmi.o -o drawtext
//		 
//	programmer: ALLAN CRUSE
//	written on: 14 SEP 2003
//-------------------------------------------------------------------

extern "C" int LRMI_init( void ), LRMI_int( int, struct LRMI_regs * );
#include "lrmi.h"	// for LRMI_init(), LRMI_int()
#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() 

#define VRAM_BASE_ADDRESS 0x000A0000
#define VGA_WINDOW_LENGTH (64 << 10)

unsigned char glyph[ 256][ 16 ];
unsigned char *vram = (unsigned char*)VRAM_BASE_ADDRESS;
int 	display_mode = 19, hres = 320, vres = 200;

void draw_character( int x, int y, int ascii, int color )
{
	unsigned char	*dstn = &vram[ y*hres + x ];
	for (int i = 0; i < 14; i++)
		{
		int	bits = glyph[ ascii ][ i ];
		for (int j = 0; j < 8; j++)
			if ( bits & ( 0x80 >> j ) ) dstn[ j ] = color;
		dstn += hres;
		}
}

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( "/dev/mem", O_RDWR );
	if ( fd < 0 ) { perror( "/dev/mem" ); exit(1); }
	if ( mmap( mm, size, prot, flag, fd, base ) == MAP_FAILED )
		{ perror( "mmap" ); exit(1); }
	close( fd );
}

int main( int argc, char **argv )
{
	if ( iopl( 3 ) ) { perror( "iopl" ); exit(1); }
	if ( !LRMI_init() ) { perror( "LRMI_init" ); exit(1); }

	// find and copy the ROM character-table to our 'glyph' array
	struct LRMI_regs  reg = {0};
	reg.eax = 0x1130;	// get font information
	reg.ebx = 0x0200;	// address of 8x14 font 
	LRMI_int( 0x10, &reg );	// BIOS service routine
	int	font_base = ( reg.es << 4 ) + ( reg.ebp & 0xFFFF );
	int	vrom_base = font_base & ~0xFFF;
	int	vrom_size = 0x1000;	// 256*32
	map_system_memory( vrom_base, vrom_size );
	int	i, j;
	unsigned char	*font = (unsigned char*)font_base;
	for (i = 0; i < 256; i++)
		for (j = 0; j < 14; j++) glyph[ i ][ j ] = *font++;
	printf( "\033[H\033[J\nfont_base: %08X \n\n", font_base );
	getchar();
	
	// map the video memory and enter graphics mode 
	int	vram_base = VRAM_BASE_ADDRESS;
	int	vram_size = VGA_WINDOW_LENGTH;
	map_system_memory( vram_base, vram_size );
	reg.eax = display_mode;
	LRMI_int( 0x10, &reg );

	// draw a 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 the screen area with a colored pattern
	color = 9;
	for (y = 1; y < vres-1; y++) for (x = 1; x < hres-1; x++)
		if (( x % 2 )&&( y % 2 )) vram[ y*hres + x ] = color;
	getchar();

	// draw some text on the patterned background 
	char	message[] = "Hello, world!";
	int	len = sizeof( message ) - 1;
	int	wide = 8*len, high = 14;
	x = ( hres - wide )/2; y = ( vres - high )/2; color = 14;
	for (i = 0; i < len; i++)
		{
		draw_character( x, y, message[i], color );
		x += 8;
		} 
	getchar();

	// restore text mode
	reg.eax = 0x0003;
	LRMI_int( 0x10, &reg );
}