Initial commit

node_modules/d3-geo/src/clip/antimeridian.js

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+import clip from "./index";
+import {abs, atan, cos, epsilon, halfPi, pi, sin} from "../math";
+
+export default clip(
+  function() { return true; },
+  clipAntimeridianLine,
+  clipAntimeridianInterpolate,
+  [-pi, -halfPi]
+);
+
+// Takes a line and cuts into visible segments. Return values: 0 - there were
+// intersections or the line was empty; 1 - no intersections; 2 - there were
+// intersections, and the first and last segments should be rejoined.
+function clipAntimeridianLine(stream) {
+  var lambda0 = NaN,
+      phi0 = NaN,
+      sign0 = NaN,
+      clean; // no intersections
+
+  return {
+    lineStart: function() {
+      stream.lineStart();
+      clean = 1;
+    },
+    point: function(lambda1, phi1) {
+      var sign1 = lambda1 > 0 ? pi : -pi,
+          delta = abs(lambda1 - lambda0);
+      if (abs(delta - pi) < epsilon) { // line crosses a pole
+        stream.point(lambda0, phi0 = (phi0 + phi1) / 2 > 0 ? halfPi : -halfPi);
+        stream.point(sign0, phi0);
+        stream.lineEnd();
+        stream.lineStart();
+        stream.point(sign1, phi0);
+        stream.point(lambda1, phi0);
+        clean = 0;
+      } else if (sign0 !== sign1 && delta >= pi) { // line crosses antimeridian
+        if (abs(lambda0 - sign0) < epsilon) lambda0 -= sign0 * epsilon; // handle degeneracies
+        if (abs(lambda1 - sign1) < epsilon) lambda1 -= sign1 * epsilon;
+        phi0 = clipAntimeridianIntersect(lambda0, phi0, lambda1, phi1);
+        stream.point(sign0, phi0);
+        stream.lineEnd();
+        stream.lineStart();
+        stream.point(sign1, phi0);
+        clean = 0;
+      }
+      stream.point(lambda0 = lambda1, phi0 = phi1);
+      sign0 = sign1;
+    },
+    lineEnd: function() {
+      stream.lineEnd();
+      lambda0 = phi0 = NaN;
+    },
+    clean: function() {
+      return 2 - clean; // if intersections, rejoin first and last segments
+    }
+  };
+}
+
+function clipAntimeridianIntersect(lambda0, phi0, lambda1, phi1) {
+  var cosPhi0,
+      cosPhi1,
+      sinLambda0Lambda1 = sin(lambda0 - lambda1);
+  return abs(sinLambda0Lambda1) > epsilon
+      ? atan((sin(phi0) * (cosPhi1 = cos(phi1)) * sin(lambda1)
+          - sin(phi1) * (cosPhi0 = cos(phi0)) * sin(lambda0))
+          / (cosPhi0 * cosPhi1 * sinLambda0Lambda1))
+      : (phi0 + phi1) / 2;
+}
+
+function clipAntimeridianInterpolate(from, to, direction, stream) {
+  var phi;
+  if (from == null) {
+    phi = direction * halfPi;
+    stream.point(-pi, phi);
+    stream.point(0, phi);
+    stream.point(pi, phi);
+    stream.point(pi, 0);
+    stream.point(pi, -phi);
+    stream.point(0, -phi);
+    stream.point(-pi, -phi);
+    stream.point(-pi, 0);
+    stream.point(-pi, phi);
+  } else if (abs(from[0] - to[0]) > epsilon) {
+    var lambda = from[0] < to[0] ? pi : -pi;
+    phi = direction * lambda / 2;
+    stream.point(-lambda, phi);
+    stream.point(0, phi);
+    stream.point(lambda, phi);
+  } else {
+    stream.point(to[0], to[1]);
+  }
+}

node_modules/d3-geo/src/clip/buffer.js

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+import noop from "../noop";
+
+export default function() {
+  var lines = [],
+      line;
+  return {
+    point: function(x, y) {
+      line.push([x, y]);
+    },
+    lineStart: function() {
+      lines.push(line = []);
+    },
+    lineEnd: noop,
+    rejoin: function() {
+      if (lines.length > 1) lines.push(lines.pop().concat(lines.shift()));
+    },
+    result: function() {
+      var result = lines;
+      lines = [];
+      line = null;
+      return result;
+    }
+  };
+}

node_modules/d3-geo/src/clip/circle.js

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+import {cartesian, cartesianAddInPlace, cartesianCross, cartesianDot, cartesianScale, spherical} from "../cartesian";
+import {circleStream} from "../circle";
+import {abs, cos, epsilon, pi, radians, sqrt} from "../math";
+import pointEqual from "../pointEqual";
+import clip from "./index";
+
+export default function(radius) {
+  var cr = cos(radius),
+      delta = 6 * radians,
+      smallRadius = cr > 0,
+      notHemisphere = abs(cr) > epsilon; // TODO optimise for this common case
+
+  function interpolate(from, to, direction, stream) {
+    circleStream(stream, radius, delta, direction, from, to);
+  }
+
+  function visible(lambda, phi) {
+    return cos(lambda) * cos(phi) > cr;
+  }
+
+  // Takes a line and cuts into visible segments. Return values used for polygon
+  // clipping: 0 - there were intersections or the line was empty; 1 - no
+  // intersections 2 - there were intersections, and the first and last segments
+  // should be rejoined.
+  function clipLine(stream) {
+    var point0, // previous point
+        c0, // code for previous point
+        v0, // visibility of previous point
+        v00, // visibility of first point
+        clean; // no intersections
+    return {
+      lineStart: function() {
+        v00 = v0 = false;
+        clean = 1;
+      },
+      point: function(lambda, phi) {
+        var point1 = [lambda, phi],
+            point2,
+            v = visible(lambda, phi),
+            c = smallRadius
+              ? v ? 0 : code(lambda, phi)
+              : v ? code(lambda + (lambda < 0 ? pi : -pi), phi) : 0;
+        if (!point0 && (v00 = v0 = v)) stream.lineStart();
+        // Handle degeneracies.
+        // TODO ignore if not clipping polygons.
+        if (v !== v0) {
+          point2 = intersect(point0, point1);
+          if (!point2 || pointEqual(point0, point2) || pointEqual(point1, point2)) {
+            point1[0] += epsilon;
+            point1[1] += epsilon;
+            v = visible(point1[0], point1[1]);
+          }
+        }
+        if (v !== v0) {
+          clean = 0;
+          if (v) {
+            // outside going in
+            stream.lineStart();
+            point2 = intersect(point1, point0);
+            stream.point(point2[0], point2[1]);
+          } else {
+            // inside going out
+            point2 = intersect(point0, point1);
+            stream.point(point2[0], point2[1]);
+            stream.lineEnd();
+          }
+          point0 = point2;
+        } else if (notHemisphere && point0 && smallRadius ^ v) {
+          var t;
+          // If the codes for two points are different, or are both zero,
+          // and there this segment intersects with the small circle.
+          if (!(c & c0) && (t = intersect(point1, point0, true))) {
+            clean = 0;
+            if (smallRadius) {
+              stream.lineStart();
+              stream.point(t[0][0], t[0][1]);
+              stream.point(t[1][0], t[1][1]);
+              stream.lineEnd();
+            } else {
+              stream.point(t[1][0], t[1][1]);
+              stream.lineEnd();
+              stream.lineStart();
+              stream.point(t[0][0], t[0][1]);
+            }
+          }
+        }
+        if (v && (!point0 || !pointEqual(point0, point1))) {
+          stream.point(point1[0], point1[1]);
+        }
+        point0 = point1, v0 = v, c0 = c;
+      },
+      lineEnd: function() {
+        if (v0) stream.lineEnd();
+        point0 = null;
+      },
+      // Rejoin first and last segments if there were intersections and the first
+      // and last points were visible.
+      clean: function() {
+        return clean | ((v00 && v0) << 1);
+      }
+    };
+  }
+
+  // Intersects the great circle between a and b with the clip circle.
+  function intersect(a, b, two) {
+    var pa = cartesian(a),
+        pb = cartesian(b);
+
+    // We have two planes, n1.p = d1 and n2.p = d2.
+    // Find intersection line p(t) = c1 n1 + c2 n2 + t (n1 ⨯ n2).
+    var n1 = [1, 0, 0], // normal
+        n2 = cartesianCross(pa, pb),
+        n2n2 = cartesianDot(n2, n2),
+        n1n2 = n2[0], // cartesianDot(n1, n2),
+        determinant = n2n2 - n1n2 * n1n2;
+
+    // Two polar points.
+    if (!determinant) return !two && a;
+
+    var c1 =  cr * n2n2 / determinant,
+        c2 = -cr * n1n2 / determinant,
+        n1xn2 = cartesianCross(n1, n2),
+        A = cartesianScale(n1, c1),
+        B = cartesianScale(n2, c2);
+    cartesianAddInPlace(A, B);
+
+    // Solve |p(t)|^2 = 1.
+    var u = n1xn2,
+        w = cartesianDot(A, u),
+        uu = cartesianDot(u, u),
+        t2 = w * w - uu * (cartesianDot(A, A) - 1);
+
+    if (t2 < 0) return;
+
+    var t = sqrt(t2),
+        q = cartesianScale(u, (-w - t) / uu);
+    cartesianAddInPlace(q, A);
+    q = spherical(q);
+
+    if (!two) return q;
+
+    // Two intersection points.
+    var lambda0 = a[0],
+        lambda1 = b[0],
+        phi0 = a[1],
+        phi1 = b[1],
+        z;
+
+    if (lambda1 < lambda0) z = lambda0, lambda0 = lambda1, lambda1 = z;
+
+    var delta = lambda1 - lambda0,
+        polar = abs(delta - pi) < epsilon,
+        meridian = polar || delta < epsilon;
+
+    if (!polar && phi1 < phi0) z = phi0, phi0 = phi1, phi1 = z;
+
+    // Check that the first point is between a and b.
+    if (meridian
+        ? polar
+          ? phi0 + phi1 > 0 ^ q[1] < (abs(q[0] - lambda0) < epsilon ? phi0 : phi1)
+          : phi0 <= q[1] && q[1] <= phi1
+        : delta > pi ^ (lambda0 <= q[0] && q[0] <= lambda1)) {
+      var q1 = cartesianScale(u, (-w + t) / uu);
+      cartesianAddInPlace(q1, A);
+      return [q, spherical(q1)];
+    }
+  }
+
+  // Generates a 4-bit vector representing the location of a point relative to
+  // the small circle's bounding box.
+  function code(lambda, phi) {
+    var r = smallRadius ? radius : pi - radius,
+        code = 0;
+    if (lambda < -r) code |= 1; // left
+    else if (lambda > r) code |= 2; // right
+    if (phi < -r) code |= 4; // below
+    else if (phi > r) code |= 8; // above
+    return code;
+  }
+
+  return clip(visible, clipLine, interpolate, smallRadius ? [0, -radius] : [-pi, radius - pi]);
+}

node_modules/d3-geo/src/clip/extent.js

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+import clipRectangle from "./rectangle";
+
+export default function() {
+  var x0 = 0,
+      y0 = 0,
+      x1 = 960,
+      y1 = 500,
+      cache,
+      cacheStream,
+      clip;
+
+  return clip = {
+    stream: function(stream) {
+      return cache && cacheStream === stream ? cache : cache = clipRectangle(x0, y0, x1, y1)(cacheStream = stream);
+    },
+    extent: function(_) {
+      return arguments.length ? (x0 = +_[0][0], y0 = +_[0][1], x1 = +_[1][0], y1 = +_[1][1], cache = cacheStream = null, clip) : [[x0, y0], [x1, y1]];
+    }
+  };
+}

node_modules/d3-geo/src/clip/index.js

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+import clipBuffer from "./buffer";
+import clipRejoin from "./rejoin";
+import {epsilon, halfPi} from "../math";
+import polygonContains from "../polygonContains";
+import {merge} from "d3-array";
+
+export default function(pointVisible, clipLine, interpolate, start) {
+  return function(sink) {
+    var line = clipLine(sink),
+        ringBuffer = clipBuffer(),
+        ringSink = clipLine(ringBuffer),
+        polygonStarted = false,
+        polygon,
+        segments,
+        ring;
+
+    var clip = {
+      point: point,
+      lineStart: lineStart,
+      lineEnd: lineEnd,
+      polygonStart: function() {
+        clip.point = pointRing;
+        clip.lineStart = ringStart;
+        clip.lineEnd = ringEnd;
+        segments = [];
+        polygon = [];
+      },
+      polygonEnd: function() {
+        clip.point = point;
+        clip.lineStart = lineStart;
+        clip.lineEnd = lineEnd;
+        segments = merge(segments);
+        var startInside = polygonContains(polygon, start);
+        if (segments.length) {
+          if (!polygonStarted) sink.polygonStart(), polygonStarted = true;
+          clipRejoin(segments, compareIntersection, startInside, interpolate, sink);
+        } else if (startInside) {
+          if (!polygonStarted) sink.polygonStart(), polygonStarted = true;
+          sink.lineStart();
+          interpolate(null, null, 1, sink);
+          sink.lineEnd();
+        }
+        if (polygonStarted) sink.polygonEnd(), polygonStarted = false;
+        segments = polygon = null;
+      },
+      sphere: function() {
+        sink.polygonStart();
+        sink.lineStart();
+        interpolate(null, null, 1, sink);
+        sink.lineEnd();
+        sink.polygonEnd();
+      }
+    };
+
+    function point(lambda, phi) {
+      if (pointVisible(lambda, phi)) sink.point(lambda, phi);
+    }
+
+    function pointLine(lambda, phi) {
+      line.point(lambda, phi);
+    }
+
+    function lineStart() {
+      clip.point = pointLine;
+      line.lineStart();
+    }
+
+    function lineEnd() {
+      clip.point = point;
+      line.lineEnd();
+    }
+
+    function pointRing(lambda, phi) {
+      ring.push([lambda, phi]);
+      ringSink.point(lambda, phi);
+    }
+
+    function ringStart() {
+      ringSink.lineStart();
+      ring = [];
+    }
+
+    function ringEnd() {
+      pointRing(ring[0][0], ring[0][1]);
+      ringSink.lineEnd();
+
+      var clean = ringSink.clean(),
+          ringSegments = ringBuffer.result(),
+          i, n = ringSegments.length, m,
+          segment,
+          point;
+
+      ring.pop();
+      polygon.push(ring);
+      ring = null;
+
+      if (!n) return;
+
+      // No intersections.
+      if (clean & 1) {
+        segment = ringSegments[0];
+        if ((m = segment.length - 1) > 0) {
+          if (!polygonStarted) sink.polygonStart(), polygonStarted = true;
+          sink.lineStart();
+          for (i = 0; i < m; ++i) sink.point((point = segment[i])[0], point[1]);
+          sink.lineEnd();
+        }
+        return;
+      }
+
+      // Rejoin connected segments.
+      // TODO reuse ringBuffer.rejoin()?
+      if (n > 1 && clean & 2) ringSegments.push(ringSegments.pop().concat(ringSegments.shift()));
+
+      segments.push(ringSegments.filter(validSegment));
+    }
+
+    return clip;
+  };
+}
+
+function validSegment(segment) {
+  return segment.length > 1;
+}
+
+// Intersections are sorted along the clip edge. For both antimeridian cutting
+// and circle clipping, the same comparison is used.
+function compareIntersection(a, b) {
+  return ((a = a.x)[0] < 0 ? a[1] - halfPi - epsilon : halfPi - a[1])
+       - ((b = b.x)[0] < 0 ? b[1] - halfPi - epsilon : halfPi - b[1]);
+}

node_modules/d3-geo/src/clip/line.js

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+export default function(a, b, x0, y0, x1, y1) {
+  var ax = a[0],
+      ay = a[1],
+      bx = b[0],
+      by = b[1],
+      t0 = 0,
+      t1 = 1,
+      dx = bx - ax,
+      dy = by - ay,
+      r;
+
+  r = x0 - ax;
+  if (!dx && r > 0) return;
+  r /= dx;
+  if (dx < 0) {
+    if (r < t0) return;
+    if (r < t1) t1 = r;
+  } else if (dx > 0) {
+    if (r > t1) return;
+    if (r > t0) t0 = r;
+  }
+
+  r = x1 - ax;
+  if (!dx && r < 0) return;
+  r /= dx;
+  if (dx < 0) {
+    if (r > t1) return;
+    if (r > t0) t0 = r;
+  } else if (dx > 0) {
+    if (r < t0) return;
+    if (r < t1) t1 = r;
+  }
+
+  r = y0 - ay;
+  if (!dy && r > 0) return;
+  r /= dy;
+  if (dy < 0) {
+    if (r < t0) return;
+    if (r < t1) t1 = r;
+  } else if (dy > 0) {
+    if (r > t1) return;
+    if (r > t0) t0 = r;
+  }
+
+  r = y1 - ay;
+  if (!dy && r < 0) return;
+  r /= dy;
+  if (dy < 0) {
+    if (r > t1) return;
+    if (r > t0) t0 = r;
+  } else if (dy > 0) {
+    if (r < t0) return;
+    if (r < t1) t1 = r;
+  }
+
+  if (t0 > 0) a[0] = ax + t0 * dx, a[1] = ay + t0 * dy;
+  if (t1 < 1) b[0] = ax + t1 * dx, b[1] = ay + t1 * dy;
+  return true;
+}

node_modules/d3-geo/src/clip/rectangle.js

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+import {abs, epsilon} from "../math";
+import clipBuffer from "./buffer";
+import clipLine from "./line";
+import clipRejoin from "./rejoin";
+import {merge} from "d3-array";
+
+var clipMax = 1e9, clipMin = -clipMax;
+
+// TODO Use d3-polygon’s polygonContains here for the ring check?
+// TODO Eliminate duplicate buffering in clipBuffer and polygon.push?
+
+export default function clipRectangle(x0, y0, x1, y1) {
+
+  function visible(x, y) {
+    return x0 <= x && x <= x1 && y0 <= y && y <= y1;
+  }
+
+  function interpolate(from, to, direction, stream) {
+    var a = 0, a1 = 0;
+    if (from == null
+        || (a = corner(from, direction)) !== (a1 = corner(to, direction))
+        || comparePoint(from, to) < 0 ^ direction > 0) {
+      do stream.point(a === 0 || a === 3 ? x0 : x1, a > 1 ? y1 : y0);
+      while ((a = (a + direction + 4) % 4) !== a1);
+    } else {
+      stream.point(to[0], to[1]);
+    }
+  }
+
+  function corner(p, direction) {
+    return abs(p[0] - x0) < epsilon ? direction > 0 ? 0 : 3
+        : abs(p[0] - x1) < epsilon ? direction > 0 ? 2 : 1
+        : abs(p[1] - y0) < epsilon ? direction > 0 ? 1 : 0
+        : direction > 0 ? 3 : 2; // abs(p[1] - y1) < epsilon
+  }
+
+  function compareIntersection(a, b) {
+    return comparePoint(a.x, b.x);
+  }
+
+  function comparePoint(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];
+  }
+
+  return function(stream) {
+    var activeStream = stream,
+        bufferStream = clipBuffer(),
+        segments,
+        polygon,
+        ring,
+        x__, y__, v__, // first point
+        x_, y_, v_, // previous point
+        first,
+        clean;
+
+    var clipStream = {
+      point: point,
+      lineStart: lineStart,
+      lineEnd: lineEnd,
+      polygonStart: polygonStart,
+      polygonEnd: polygonEnd
+    };
+
+    function point(x, y) {
+      if (visible(x, y)) activeStream.point(x, y);
+    }
+
+    function polygonInside() {
+      var winding = 0;
+
+      for (var i = 0, n = polygon.length; i < n; ++i) {
+        for (var ring = polygon[i], j = 1, m = ring.length, point = ring[0], a0, a1, b0 = point[0], b1 = point[1]; j < m; ++j) {
+          a0 = b0, a1 = b1, point = ring[j], b0 = point[0], b1 = point[1];
+          if (a1 <= y1) { if (b1 > y1 && (b0 - a0) * (y1 - a1) > (b1 - a1) * (x0 - a0)) ++winding; }
+          else { if (b1 <= y1 && (b0 - a0) * (y1 - a1) < (b1 - a1) * (x0 - a0)) --winding; }
+        }
+      }
+
+      return winding;
+    }
+
+    // Buffer geometry within a polygon and then clip it en masse.
+    function polygonStart() {
+      activeStream = bufferStream, segments = [], polygon = [], clean = true;
+    }
+
+    function polygonEnd() {
+      var startInside = polygonInside(),
+          cleanInside = clean && startInside,
+          visible = (segments = merge(segments)).length;
+      if (cleanInside || visible) {
+        stream.polygonStart();
+        if (cleanInside) {
+          stream.lineStart();
+          interpolate(null, null, 1, stream);
+          stream.lineEnd();
+        }
+        if (visible) {
+          clipRejoin(segments, compareIntersection, startInside, interpolate, stream);
+        }
+        stream.polygonEnd();
+      }
+      activeStream = stream, segments = polygon = ring = null;
+    }
+
+    function lineStart() {
+      clipStream.point = linePoint;
+      if (polygon) polygon.push(ring = []);
+      first = true;
+      v_ = false;
+      x_ = y_ = NaN;
+    }
+
+    // TODO rather than special-case polygons, simply handle them separately.
+    // Ideally, coincident intersection points should be jittered to avoid
+    // clipping issues.
+    function lineEnd() {
+      if (segments) {
+        linePoint(x__, y__);
+        if (v__ && v_) bufferStream.rejoin();
+        segments.push(bufferStream.result());
+      }
+      clipStream.point = point;
+      if (v_) activeStream.lineEnd();
+    }
+
+    function linePoint(x, y) {
+      var v = visible(x, y);
+      if (polygon) ring.push([x, y]);
+      if (first) {
+        x__ = x, y__ = y, v__ = v;
+        first = false;
+        if (v) {
+          activeStream.lineStart();
+          activeStream.point(x, y);
+        }
+      } else {
+        if (v && v_) activeStream.point(x, y);
+        else {
+          var a = [x_ = Math.max(clipMin, Math.min(clipMax, x_)), y_ = Math.max(clipMin, Math.min(clipMax, y_))],
+              b = [x = Math.max(clipMin, Math.min(clipMax, x)), y = Math.max(clipMin, Math.min(clipMax, y))];
+          if (clipLine(a, b, x0, y0, x1, y1)) {
+            if (!v_) {
+              activeStream.lineStart();
+              activeStream.point(a[0], a[1]);
+            }
+            activeStream.point(b[0], b[1]);
+            if (!v) activeStream.lineEnd();
+            clean = false;
+          } else if (v) {
+            activeStream.lineStart();
+            activeStream.point(x, y);
+            clean = false;
+          }
+        }
+      }
+      x_ = x, y_ = y, v_ = v;
+    }
+
+    return clipStream;
+  };
+}

node_modules/d3-geo/src/clip/rejoin.js

@@ -0,0 +1,101 @@
+import pointEqual from "../pointEqual";
+
+function Intersection(point, points, other, entry) {
+  this.x = point;
+  this.z = points;
+  this.o = other; // another intersection
+  this.e = entry; // is an entry?
+  this.v = false; // visited
+  this.n = this.p = null; // next & previous
+}
+
+// A generalized polygon clipping algorithm: given a polygon that has been cut
+// into its visible line segments, and rejoins the segments by interpolating
+// along the clip edge.
+export default function(segments, compareIntersection, startInside, interpolate, stream) {
+  var subject = [],
+      clip = [],
+      i,
+      n;
+
+  segments.forEach(function(segment) {
+    if ((n = segment.length - 1) <= 0) return;
+    var n, p0 = segment[0], p1 = segment[n], x;
+
+    // If the first and last points of a segment are coincident, then treat as a
+    // closed ring. TODO if all rings are closed, then the winding order of the
+    // exterior ring should be checked.
+    if (pointEqual(p0, p1)) {
+      stream.lineStart();
+      for (i = 0; i < n; ++i) stream.point((p0 = segment[i])[0], p0[1]);
+      stream.lineEnd();
+      return;
+    }
+
+    subject.push(x = new Intersection(p0, segment, null, true));
+    clip.push(x.o = new Intersection(p0, null, x, false));
+    subject.push(x = new Intersection(p1, segment, null, false));
+    clip.push(x.o = new Intersection(p1, null, x, true));
+  });
+
+  if (!subject.length) return;
+
+  clip.sort(compareIntersection);
+  link(subject);
+  link(clip);
+
+  for (i = 0, n = clip.length; i < n; ++i) {
+    clip[i].e = startInside = !startInside;
+  }
+
+  var start = subject[0],
+      points,
+      point;
+
+  while (1) {
+    // Find first unvisited intersection.
+    var current = start,
+        isSubject = true;
+    while (current.v) if ((current = current.n) === start) return;
+    points = current.z;
+    stream.lineStart();
+    do {
+      current.v = current.o.v = true;
+      if (current.e) {
+        if (isSubject) {
+          for (i = 0, n = points.length; i < n; ++i) stream.point((point = points[i])[0], point[1]);
+        } else {
+          interpolate(current.x, current.n.x, 1, stream);
+        }
+        current = current.n;
+      } else {
+        if (isSubject) {
+          points = current.p.z;
+          for (i = points.length - 1; i >= 0; --i) stream.point((point = points[i])[0], point[1]);
+        } else {
+          interpolate(current.x, current.p.x, -1, stream);
+        }
+        current = current.p;
+      }
+      current = current.o;
+      points = current.z;
+      isSubject = !isSubject;
+    } while (!current.v);
+    stream.lineEnd();
+  }
+}
+
+function link(array) {
+  if (!(n = array.length)) return;
+  var n,
+      i = 0,
+      a = array[0],
+      b;
+  while (++i < n) {
+    a.n = b = array[i];
+    b.p = a;
+    a = b;
+  }
+  a.n = b = array[0];
+  b.p = a;
+}