Function line_dist_coord

src/selvar.c:541–566

square of distance from line segment (x1,y1, x2,y2) to point (x3,y3) */

/* square of distance from line segment (x1,y1, x2,y2) to point (x3,y3) */
staticfn long
line_dist_coord(long x1, long y1, long x2, long y2, long x3, long y3)
{
    long px = x2 - x1;
    long py = y2 - y1;
    long s = px * px + py * py;
    long x, y, dx, dy, distsq = 0;
    float lu = 0;

    if (x1 == x2 && y1 == y2)
        return dist2(x1, y1, x3, y3);

    lu = ((x3 - x1) * px + (y3 - y1) * py) / (float) s;
    if (lu > 1)
        lu = 1;
    else if (lu < 0)
        lu = 0;

    x = x1 + lu * px;
    y = y1 + lu * py;
    dx = x - x3;
    dy = y - y3;
    distsq = dx * dx + dy * dy;

    return distsq;
}

/* guts of l_selection_gradient */
void