wm: teppich

ref: 086331e6bf7b682b12ca392130160a1afb371f12
dir: /pc/vga.c/

#include <u.h>
#include <libc.h>
#include <vga.h>

static inline uint8
vga_gencolor(int fg, int bg)
{
	return fg | bg << 4;
}

static inline uint16
vga_char(unsigned char c, uint8 color)
{
	return (uint16) c | (uint16) color << 8;
}

void
vga_clear(char c)
{
	for (size_t y = 0; y < VGA_HEIGHT; y++)
	{
		for (size_t x = 0; x < VGA_WIDTH; x++)
		{
			uint16 index = y * VGA_WIDTH + x;
			vga_buf[index] = vga_char(c, vga_color);
		}
	}
	vga_row = 0;
	vga_col = 0;
}

void
vga_init(int fg, int bg)
{
	vga_row = 0;
	vga_col = 0;
	vga_color = vga_gencolor(fg, bg);
	vga_buf = (uint16*) 0xB8000;
	vga_clear(' ');
}

void
vga_writeto(char c, uint8 color, int x, int y)
{
	int index = y * VGA_WIDTH + x;
	vga_buf[index] = vga_char(c, color);
}


void
vga_nl(void)
{
	vga_col = 0; /* cr */
	if(++vga_row == VGA_HEIGHT) /* lf */
		vga_row = 0;
	
}

void
vga_putc(char c)
{
	int index = vga_row * VGA_WIDTH + vga_col;
	switch(c)
	{
		case '\r':
		case '\n':
			vga_nl();
			return;
		case '\t':
			for(int i = 0 ; i < 4 ; i++)
				vga_putc(' ');
			return;
		case '\b':
			if(vga_col > 0)
			{
				/* index points at current loction of cursor, which is empty. */
				vga_buf[index - 1] = vga_char(' ', vga_color);
				vga_col--;
			}

			/*
			is the following needed? i wonder.
			i'm aware of no OSes that allow their raw terminal interface
			allow returing to previous lines.
			only Plan 9 console driver allows this on rio.

			maybe it's safer to skip it.... for now.

			else if(vga_row == 0)
			{
			// we need a smarter terminal-ish version
			//		smh like
			//		vga_row = vga_find_last_nonchar(' ');

				vga_row = VGA_WIDTH;
			}
			*/

			return;
		default:
			vga_writeto(c, vga_color, vga_col, vga_row);
			if(++vga_col == VGA_WIDTH)
			vga_nl();
	}
}

void
vga_puts(char *s)
{
	int len = strlen(s);
	for(int i = 0 ; i < len ; i++)
		vga_putc(s[i]);
}