quark/src/kernel/drivers/vga.c

#include "vga.h"
#include "../arch/i686/io.h"

static uint8_t current_color = VGA_COLOR_BG_BLACK | VGA_COLOR_FG_WHITE;

void set_char(int x, int y, char c){
    VGA_MEMORY[(x+y*VGA_WIDTH)*2] = c;
}

void set_color(int x, int y, uint8_t color){
    VGA_MEMORY[(x+y*VGA_WIDTH)*2+1] = color;
}

void set_cursor(int offset){
    i686_outb(VGA_PORT_CTRL, 14);
    i686_outb(VGA_PORT_DATA, (uint8_t)(offset >> 8));
    i686_outb(VGA_PORT_CTRL, 15);
    i686_outb(VGA_PORT_DATA, (uint8_t)(offset & 0xff));
}

int get_cursor(){
    i686_outb(VGA_PORT_CTRL, 14);
    int offset = i686_inb(VGA_PORT_DATA) << 8; // High byte
    i686_outb(VGA_PORT_CTRL, 15);
    offset += i686_inb(VGA_PORT_DATA); // Low byte
    return offset;
}

static int get_offset_y(int offset){
    return offset / VGA_WIDTH;
}

static int get_offset_x(int offset){
    return (offset - (get_offset_y(offset)*VGA_WIDTH));
}

int print_char(char c, int x, int y){
    if(x >= VGA_WIDTH || y >= VGA_HEIGHT){ // Incorrect coords
        VGA_MEMORY[2*VGA_WIDTH*VGA_HEIGHT-2] = 'E';
        VGA_MEMORY[2*VGA_WIDTH*VGA_HEIGHT-1] = VGA_COLOR_BG_RED || VGA_COLOR_FG_BLACK;
        return y*VGA_WIDTH+x;
    }

    int offset;
    if(x >= 0 && y >= 0) offset = y*VGA_WIDTH+x;
    else offset = get_cursor();

    if(c == '\n'){
        y = get_offset_y(offset);
        offset = (y+1)*VGA_WIDTH;
    }
    else if(c == '\b'){
        VGA_MEMORY[offset*2] = ' ';
        VGA_MEMORY[offset*2+1] = current_color;
    }
    else{
        VGA_MEMORY[offset*2] = c;
        VGA_MEMORY[offset*2+1] = current_color;
        offset++;
    }

    // TODO: Scroll
    
    set_cursor(offset);
    return offset;
}

void print_string_at(char *str, int x, int y){
    int offset;
    if(x >= 0 && y >= 0){
        offset = y*VGA_WIDTH+x;
    }
    else{
        offset = get_cursor();
        x = get_offset_x(offset);
        y = get_offset_y(offset);
    }

    while(*str){
        offset = print_char(*(str++), x, y);
        x = get_offset_x(offset);
        y = get_offset_y(offset);
    }
}

void print_string(char *str){
    print_string_at(str, -1, -1);
}