eOS/drivers/vga.c

// VGA Graphics Library
#include "vga.h"
#include "../kernel/io.h"
#include "../lib/str.h"

static unsigned int cursor_row = 0;
static unsigned int cursor_col = 0;

void vga_init() {
	// Disable cursor
	port_outb(0x3d4, 0x0a);
	port_outb(0x3d5, 0x20);

	// Clear screen
	clear_screen();
}

/*
	VGA & Memory Functions
*/
char* get_memory_charpos(unsigned int col, unsigned int row) { 
	return (char*)(VGA_ADDRESS + 2*((row*80) + col)); 
}

void writechar(char c, unsigned int col, unsigned int row, int attribute_byte) {
	if( !attribute_byte ) 
		attribute_byte = DEFAULT_COLOR;

	char* mem = get_memory_charpos(col, row);
	*mem = c; 			// Write the character
	*(mem+1) = attribute_byte;	// Write the attribute_byte

}

void set_cursor_pos(unsigned int col, unsigned int row) {
	cursor_col = col;
	cursor_row = row;
}


/*
	Graphics Functions
*/
void clear_screen() {
	for( int c = 0; c < MAX_COLS; c++ )
		for( int r = 0; r < MAX_ROWS; r++ )
			writechar(0x20, c, r, 0x0);
}

/*
	General Printing Functions
*/
void print(char* str, int attribute_byte) {
	for( char* c = str; *c != '\0'; c++ ) 
		writechar(*c, (unsigned int)(c - str) + cursor_col, cursor_row, attribute_byte);
}

void println(char* str, int attribute_byte) {
	print(str, attribute_byte);
	cursor_row++; // Increment to next y-pos (newline)
}

void printalign(char* str, int attribute_byte, enum align alignment) {
	unsigned int strlenbuf = strlen(str);

	if( !alignment || alignment == LEFT ) {
		print(str, attribute_byte);
	} else if ( alignment == RIGHT ) {
		set_cursor_pos(MAX_COLS - strlenbuf, cursor_row);
	} else if ( alignment == MIDDLE ) {
		set_cursor_pos((MAX_COLS/2) - (strlenbuf/2), cursor_row);
	}

	print(str, attribute_byte);
}