static void ICODE_ATTR draw_antialiased_line(int x0, int y0, int x1, int y1)
{
    /* fixed-point Wu's algorithm, modified for integer-only endpoints */

    /* passed to plot() to avoid re-calculation */
    unsigned short l = 0, r = LCD_WIDTH, u = 0, d = LCD_HEIGHT;
    if(clipped)
    {
        l = clip_rect.x;
        r = clip_rect.x + clip_rect.width;
        u = clip_rect.y;
        d = clip_rect.y + clip_rect.height;
    }

    bool steep = ABS(y1 - y0) > ABS(x1 - x0);
    int tmp;
    if(steep)
    {
        SWAP(x0, y0, tmp);
        SWAP(x1, y1, tmp);
    }
    if(x0 > x1)
    {
        SWAP(x0, x1, tmp);
        SWAP(y0, y1, tmp);
    }

    int dx, dy;
    dx = x1 - x0;
    dy = y1 - y0;

    if(!(dx << FRACBITS))
        return; /* bail out */

    long gradient = fp_div(dy << FRACBITS, dx << FRACBITS, FRACBITS);
    long intery = (y0 << FRACBITS);

    unsigned color = rb->lcd_get_foreground();
    unsigned long r1, g1, b1;
    r1 = RGB_UNPACK_RED(color);
    g1 = RGB_UNPACK_GREEN(color);
    b1 = RGB_UNPACK_BLUE(color);

    /* main loop */
    if(steep)
    {
        for(int x = x0; x <= x1; ++x, intery += gradient)
        {
            unsigned y = intery >> FRACBITS;
            unsigned alpha = fp_fpart(intery, FRACBITS) >> (FRACBITS - 8);

            plot(y, x, (1 << 8) - alpha, r1, g1, b1, l, r, u, d);
            plot(y + 1, x, alpha, r1, g1, b1, l, r, u, d);
        }
    }
    else
    {
        for(int x = x0; x <= x1; ++x, intery += gradient)
        {
            unsigned y = intery >> FRACBITS;
            unsigned alpha = fp_fpart(intery, FRACBITS) >> (FRACBITS - 8);

            plot(x, y, (1 << 8) - alpha, r1, g1, b1, l, r, u, d);
            plot(x, y + 1, alpha, r1, g1, b1, l, r, u, d);
        }
    }
}