//-------------------------------------------------------------------
//	twofonts.cpp
//
//	This program illustrates the simultaneous use of two glyph-
//	tables by the VGA's text-mode character-generator mechanism
//	after reprogramming the Attribute Controller's 'Color Plane
//	Enable' register to disable Color Plane 3 (intense colors).  
//
//	   compile using:  $ twofonts.cpp int86.cpp -o twofonts
//
//	programmer: ALLAN CRUSE
//	written on: 08 SEP 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf()  
#include <string.h>	// for strlen()
#include <unistd.h>	// for STDIN_FILENO 
#include <sys/io.h>	// for inb(), outb(), etc.
#include <termios.h>	// for tcgetattr(), tcsetattr()
#include "int86.h"	// for init8086(), int86()

#define	VRAM_BASE_FOR_CGA  0x000B8000 

typedef unsigned char u8; 

typedef struct { unsigned char	character, attribute; } CELL;

CELL *vram = (CELL*)VRAM_BASE_FOR_CGA; 
struct vm86plus_struct	vm; 

int main( int argc, char **argv )
{	
	// setup the keyboard for 'non-canonical' input
	struct termios	orig_tty;
	tcgetattr( STDIN_FILENO, &orig_tty );
	struct termios	work_tty = orig_tty;
	work_tty.c_lflag &= ~(ICANON | ECHO );
	work_tty.c_cc[ VTIME ] = 0;
	work_tty.c_cc[ VMIN ] = 1;
	tcsetattr( STDIN_FILENO, TCSAFLUSH, &work_tty );

	// set the CRT Start_Address to zero 
	init8086();			// enable BIOS access
	vm.regs.eax = 0x0003;		// Set Display Mode 3
	int86( 0x10, vm );		// invoke BIOS service
	CELL	*dstn = vram;		// address top of screen 

	// create text-cells for directly writing to video memory	
	char	message1[] = "Hello, folks!";
	char	message2[] = "This is a VGA character generator demonstration";
	CELL	font[ 512 ];		// for showing 512-glyphs 
	for (int i = 0; i < 512; i++)
		{
		font[ i ].character = (i & 0xFF);
		font[ i ].attribute = (i < 256) ? 0x07 : 0x0F;
		}
	
	// copy text-cells directly to video memory	
	dstn += 80;
	for (int i = 0; i < strlen( message1 ); i++)
		dstn[ i ].character = message1[ i ];
	dstn += 80;
	for (int i = 0; i < strlen( message2 ); i++)
		dstn[ i ].character = message2[ i ];
	getchar();
	dstn += 2*80;
	for (int i = 0; i < 512; i++)
		{
		if ( ( i % 32 ) == 0 ) dstn += 80;
		dstn[ 2*(i % 32) + 8 ] = font[ i ];
		}
	getchar();			

	// invoke BIOS function to load a different font-table
	vm.regs.eax = 0x1102;	// Load 8x8 font-table
	vm.regs.ebx = 0x0001;	// into generator map 1
	int86( 0x10, vm );	// invoke BIOS service
	getchar();

	// switch to new font-table as the Primary Font
	vm.regs.eax = 0x1103;	// Select the Active Maps 
	vm.regs.ebx = 0x0001;	// 1 Primary, 0 secondary
	int86( 0x10, vm );	// invoke BIOS service
	getchar();	

	// set intensity-bit of alternating cells in top four rows
	for (int i = 0; i < 320; i++) vram[ 2*i+1 ].attribute |= 0x08;
	getchar();

	// Attribute Controller Color Plane Enable register (index 0x12)
	inb( 0x3DA );		// reset the controller's flip-flop
	outb( 0x12, 0x3C0 );	// select Color Plane Enable register 
	outb( 0x07, 0x3C0 );	// write new Color Plane Enable value
	outb( 0x20, 0x3C0 );	// set Index bit #5 (reenable screen) 
	getchar();

	// restore canonical keyboard-input and reinitialize text-mode 
	tcsetattr( STDIN_FILENO, TCSAFLUSH, &orig_tty );
	vm.regs.eax = 0x0003;		// Set Display Mode 3
	int86( 0x10, vm );		// invoke BIOS service
	printf( "\n" );			// advance to new line
}