Function comparePoints

d3-3.2.8/d3.js:3021–3024

(a, b)

      return comparePoints(a.point, b.point);
    }
    function comparePoints(a, b) {
      var ca = corner(a, 1), cb = corner(b, 1);
      return ca !== cb ? ca - cb : ca === 0 ? b[1] - a[1] : ca === 1 ? a[0] - b[0] : ca === 2 ? a[1] - b[1] : b[0] - a[0];
    }
    function clipLine(a, b) {
      var dx = b[0] - a[0], dy = b[1] - a[1], t = [ 0, 1 ];
      if (Math.abs(dx) < ε && Math.abs(dy) < ε) return x0 <= a[0] && a[0] <= x1 && y0 <= a[1] && a[1] <= y1;