d3.js

// Matrix to transform basis (b-spline) control points to bezier
// control points. Derived from FvD 11.2.8.
var d3_svg_lineBasisBezier1 = [0, 2/3, 1/3, 0],
    d3_svg_lineBasisBezier2 = [0, 1/3, 2/3, 0],
    d3_svg_lineBasisBezier3 = [0, 1/6, 2/3, 1/6];

// Pushes a "C" Bézier curve onto the specified path array, given the
// two specified four-element arrays which define the control points.
function d3_svg_lineBasisBezier(path, x, y) {
  path.push(
      "C", d3_svg_lineDot4(d3_svg_lineBasisBezier1, x),
      ",", d3_svg_lineDot4(d3_svg_lineBasisBezier1, y),
      ",", d3_svg_lineDot4(d3_svg_lineBasisBezier2, x),
      ",", d3_svg_lineDot4(d3_svg_lineBasisBezier2, y),
      ",", d3_svg_lineDot4(d3_svg_lineBasisBezier3, x),
      ",", d3_svg_lineDot4(d3_svg_lineBasisBezier3, y));
}

// Computes the slope from points p0 to p1.
function d3_svg_lineSlope(p0, p1) {
  return (p1[1] - p0[1]) / (p1[0] - p0[0]);
}

// Compute three-point differences for the given points.
// http://en.wikipedia.org/wiki/Cubic_Hermite_spline#Finite_difference
function d3_svg_lineFiniteDifferences(points) {
  var i = 0,
      j = points.length - 1,
      m = [],
      p0 = points[0],
      p1 = points[1],
      d = m[0] = d3_svg_lineSlope(p0, p1);
  while (++i < j) {
    m[i] = d + (d = d3_svg_lineSlope(p0 = p1, p1 = points[i + 1]));
  }
  m[i] = d;
  return m;
}

// Interpolates the given points using Fritsch-Carlson Monotone cubic Hermite
// interpolation. Returns an array of tangent vectors. For details, see
// http://en.wikipedia.org/wiki/Monotone_cubic_interpolation
function d3_svg_lineMonotoneTangents(points) {
  var tangents = [],
      d,
      a,
      b,
      s,
      m = d3_svg_lineFiniteDifferences(points),
      i = -1,
      j = points.length - 1;

  // The first two steps are done by computing finite-differences:
  // 1. Compute the slopes of the secant lines between successive points.
  // 2. Initialize the tangents at every point as the average of the secants.

  // Then, for each segment…
  while (++i < j) {
    d = d3_svg_lineSlope(points[i], points[i + 1]);

    // 3. If two successive yk = y{k + 1} are equal (i.e., d is zero), then set
    // mk = m{k + 1} = 0 as the spline connecting these points must be flat to
    // preserve monotonicity. Ignore step 4 and 5 for those k.

    if (Math.abs(d) < 1e-6) {
      m[i] = m[i + 1] = 0;
    } else {
      // 4. Let ak = mk / dk and bk = m{k + 1} / dk.
      a = m[i] / d;
      b = m[i + 1] / d;

      // 5. Prevent overshoot and ensure monotonicity by restricting the
      // magnitude of vector <ak, bk> to a circle of radius 3.
      s = a * a + b * b;
      if (s > 9) {
        s = d * 3 / Math.sqrt(s);
        m[i] = s * a;
        m[i + 1] = s * b;
      }
    }
  }

  // Compute the normalized tangent vector from the slopes. Note that if x is
  // not monotonic, it's possible that the slope will be infinite, so we protect
  // against NaN by setting the coordinate to zero.
  i = -1; while (++i <= j) {
    s = (points[Math.min(j, i + 1)][0] - points[Math.max(0, i - 1)][0])
      / (6 * (1 + m[i] * m[i]));
    tangents.push([s || 0, m[i] * s || 0]);
  }

  return tangents;
}

function d3_svg_lineMonotone(points) {
  return points.length < 3
      ? d3_svg_lineLinear(points)
      : points[0] +
        d3_svg_lineHermite(points, d3_svg_lineMonotoneTangents(points));
}
d3.svg.line.radial = function() {
  var line = d3_svg_line(d3_svg_lineRadial);
  line.radius = line.x, delete line.x;
  line.angle = line.y, delete line.y;
  return line;
};

function d3_svg_lineRadial(points) {
  var point,
      i = -1,
      n = points.length,
      r,
      a;
  while (++i < n) {
    point = points[i];
    r = point[0];
    a = point[1] + d3_svg_arcOffset;
    point[0] = r * Math.cos(a);
    point[1] = r * Math.sin(a);
  }
  return points;
}
function d3_svg_area(projection) {
  var x0 = d3_svg_lineX,
      x1 = d3_svg_lineX,
      y0 = 0,
      y1 = d3_svg_lineY,
      interpolate = "linear",
      interpolator = d3_svg_lineInterpolators[interpolate],
      tension = .7;

  function area(d) {
    if (d.length < 1) return null;
    var points0 = d3_svg_linePoints(this, d, x0, y0),
        points1 = d3_svg_linePoints(this, d, x0 === x1 ? d3_svg_areaX(points0) : x1, y0 === y1 ? d3_svg_areaY(points0) : y1);
    return "M" + interpolator(projection(points1), tension)
         + "L" + interpolator(projection(points0.reverse()), tension)
         + "Z";
  }

  area.x = function(x) {
    if (!arguments.length) return x1;
    x0 = x1 = x;
    return area;
  };

  area.x0 = function(x) {
    if (!arguments.length) return x0;
    x0 = x;
    return area;
  };

  area.x1 = function(x) {
    if (!arguments.length) return x1;
    x1 = x;
    return area;
  };

  area.y = function(y) {
    if (!arguments.length) return y1;
    y0 = y1 = y;
    return area;
  };

  area.y0 = function(y) {
    if (!arguments.length) return y0;
    y0 = y;
    return area;
  };

  area.y1 = function(y) {
    if (!arguments.length) return y1;
    y1 = y;
    return area;
  };

  area.interpolate = function(x) {
    if (!arguments.length) return interpolate;
    interpolator = d3_svg_lineInterpolators[interpolate = x];
    return area;
  };

  area.tension = function(x) {
    if (!arguments.length) return tension;
    tension = x;
    return area;
  };

  return area;
}

d3.svg.area = function() {
  return d3_svg_area(Object);
};

function d3_svg_areaX(points) {
  return function(d, i) {
    return points[i][0];
  };
}

function d3_svg_areaY(points) {
  return function(d, i) {
    return points[i][1];
  };
}
d3.svg.area.radial = function() {
  var area = d3_svg_area(d3_svg_lineRadial);
  area.radius = area.x, delete area.x;
  area.innerRadius = area.x0, delete area.x0;
  area.outerRadius = area.x1, delete area.x1;
  area.angle = area.y, delete area.y;
  area.startAngle = area.y0, delete area.y0;
  area.endAngle = area.y1, delete area.y1;
  return area;
};
d3.svg.chord = function() {
  var source = d3_svg_chordSource,
      target = d3_svg_chordTarget,
      radius = d3_svg_chordRadius,
      startAngle = d3_svg_arcStartAngle,
      endAngle = d3_svg_arcEndAngle;

  // TODO Allow control point to be customized.

  function chord(d, i) {
    var s = subgroup(this, source, d, i),
        t = subgroup(this, target, d, i);
    return "M" + s.p0
      + arc(s.r, s.p1) + (equals(s, t)
      ? curve(s.r, s.p1, s.r, s.p0)
      : curve(s.r, s.p1, t.r, t.p0)
      + arc(t.r, t.p1)
      + curve(t.r, t.p1, s.r, s.p0))
      + "Z";
  }

  function subgroup(self, f, d, i) {
    var subgroup = f.call(self, d, i),
        r = radius.call(self, subgroup, i),
        a0 = startAngle.call(self, subgroup, i) + d3_svg_arcOffset,
        a1 = endAngle.call(self, subgroup, i) + d3_svg_arcOffset;
    return {
      r: r,
      a0: a0,
      a1: a1,
      p0: [r * Math.cos(a0), r * Math.sin(a0)],
      p1: [r * Math.cos(a1), r * Math.sin(a1)]
    };
  }

  function equals(a, b) {
    return a.a0 == b.a0 && a.a1 == b.a1;
  }

  function arc(r, p) {
    return "A" + r + "," + r + " 0 0,1 " + p;
  }

  function curve(r0, p0, r1, p1) {
    return "Q 0,0 " + p1;
  }

  chord.radius = function(v) {
    if (!arguments.length) return radius;
    radius = d3.functor(v);
    return chord;
  };

  chord.source = function(v) {
    if (!arguments.length) return source;
    source = d3.functor(v);
    return chord;
  };

  chord.target = function(v) {
    if (!arguments.length) return target;
    target = d3.functor(v);
    return chord;
  };

  chord.startAngle = function(v) {
    if (!arguments.length) return startAngle;
    startAngle = d3.functor(v);
    return chord;
  };

  chord.endAngle = function(v) {
    if (!arguments.length) return endAngle;
    endAngle = d3.functor(v);
    return chord;
  };

  return chord;
};

function d3_svg_chordSource(d) {
  return d.source;
}

function d3_svg_chordTarget(d) {
  return d.target;
}

function d3_svg_chordRadius(d) {
  return d.radius;
}

function d3_svg_chordStartAngle(d) {
  return d.startAngle;
}

function d3_svg_chordEndAngle(d) {
  return d.endAngle;
}
d3.svg.diagonal = function() {
  var source = d3_svg_chordSource,
      target = d3_svg_chordTarget,
      projection = d3_svg_diagonalProjection;

  function diagonal(d, i) {
    var p0 = source.call(this, d, i),
        p3 = target.call(this, d, i),
        m = (p0.y + p3.y) / 2,
        p = [p0, {x: p0.x, y: m}, {x: p3.x, y: m}, p3];
    p = p.map(projection);
    return "M" + p[0] + "C" + p[1] + " " + p[2] + " " + p[3];
  }

  diagonal.source = function(x) {
    if (!arguments.length) return source;
    source = d3.functor(x);
    return diagonal;
  };

  diagonal.target = function(x) {
    if (!arguments.length) return target;
    target = d3.functor(x);
    return diagonal;
  };

  diagonal.projection = function(x) {
    if (!arguments.length) return projection;
    projection = x;
    return diagonal;
  };

  return diagonal;
};

function d3_svg_diagonalProjection(d) {
  return [d.x, d.y];
}
d3.svg.diagonal.radial = function() {
  var diagonal = d3.svg.diagonal(),
      projection = d3_svg_diagonalProjection,
      projection_ = diagonal.projection;

  diagonal.projection = function(x) {
    return arguments.length
        ? projection_(d3_svg_diagonalRadialProjection(projection = x))
        : projection;
  };

  return diagonal;
};

function d3_svg_diagonalRadialProjection(projection) {
  return function() {
    var d = projection.apply(this, arguments),
        r = d[0],
        a = d[1] + d3_svg_arcOffset;
    return [r * Math.cos(a), r * Math.sin(a)];
  };
}
d3.svg.mouse = function(container) {
  return d3_svg_mousePoint(container, d3.event);
};

// https://bugs.webkit.org/show_bug.cgi?id=44083
var d3_mouse_bug44083 = /WebKit/.test(navigator.userAgent) ? -1 : 0;

function d3_svg_mousePoint(container, e) {
  var point = (container.ownerSVGElement || container).createSVGPoint();
  if ((d3_mouse_bug44083 < 0) && (window.scrollX || window.scrollY)) {
    var svg = d3.select(document.body)
      .append("svg:svg")
        .style("position", "absolute")
        .style("top", 0)
        .style("left", 0);
    var ctm = svg[0][0].getScreenCTM();
    d3_mouse_bug44083 = !(ctm.f || ctm.e);
    svg.remove();
  }
  if (d3_mouse_bug44083) {
    point.x = e.pageX;
    point.y = e.pageY;
  } else {
    point.x = e.clientX;
    point.y = e.clientY;
  }
  point = point.matrixTransform(container.getScreenCTM().inverse());
  return [point.x, point.y];
};
d3.svg.touches = function(container) {
  var touches = d3.event.touches;
  return touches ? Array.prototype.map.call(touches, function(touch) {
    var point = d3_svg_mousePoint(container, touch);
    point.identifier = touch.identifier;
    return point;
  }) : [];
};
d3.svg.symbol = function() {
  var type = d3_svg_symbolType,
      size = d3_svg_symbolSize;

  function symbol(d, i) {
    return (d3_svg_symbols[type.call(this, d, i)]
        || d3_svg_symbols.circle)
        (size.call(this, d, i));
  }

  symbol.type = function(x) {
    if (!arguments.length) return type;
    type = d3.functor(x);
    return symbol;
  };

  // size of symbol in square pixels
  symbol.size = function(x) {
    if (!arguments.length) return size;
    size = d3.functor(x);
    return symbol;
  };

  return symbol;
};

function d3_svg_symbolSize() {
  return 64;
}

function d3_svg_symbolType() {
  return "circle";
}

// TODO cross-diagonal?
var d3_svg_symbols = {
  "circle": function(size) {
    var r = Math.sqrt(size / Math.PI);
    return "M0," + r
        + "A" + r + "," + r + " 0 1,1 0," + (-r)
        + "A" + r + "," + r + " 0 1,1 0," + r
        + "Z";
  },
  "cross": function(size) {
    var r = Math.sqrt(size / 5) / 2;
    return "M" + -3 * r + "," + -r
        + "H" + -r
        + "V" + -3 * r
        + "H" + r
        + "V" + -r
        + "H" + 3 * r
        + "V" + r
        + "H" + r
        + "V" + 3 * r
        + "H" + -r
        + "V" + r
        + "H" + -3 * r
        + "Z";
  },
  "diamond": function(size) {
    var ry = Math.sqrt(size / (2 * d3_svg_symbolTan30)),
        rx = ry * d3_svg_symbolTan30;
    return "M0," + -ry
        + "L" + rx + ",0"
        + " 0," + ry
        + " " + -rx + ",0"
        + "Z";
  },
  "square": function(size) {
    var r = Math.sqrt(size) / 2;
    return "M" + -r + "," + -r
        + "L" + r + "," + -r
        + " " + r + "," + r
        + " " + -r + "," + r
        + "Z";
  },
  "triangle-down": function(size) {
    var rx = Math.sqrt(size / d3_svg_symbolSqrt3),
        ry = rx * d3_svg_symbolSqrt3 / 2;
    return "M0," + ry
        + "L" + rx +"," + -ry
        + " " + -rx + "," + -ry
        + "Z";
  },
  "triangle-up": function(size) {
    var rx = Math.sqrt(size / d3_svg_symbolSqrt3),
        ry = rx * d3_svg_symbolSqrt3 / 2;
    return "M0," + -ry
        + "L" + rx +"," + ry
        + " " + -rx + "," + ry
        + "Z";
  }
};

d3.svg.symbolTypes = d3.keys(d3_svg_symbols);

var d3_svg_symbolSqrt3 = Math.sqrt(3),
    d3_svg_symbolTan30 = Math.tan(30 * Math.PI / 180);
d3.svg.axis = function() {
  var scale = d3.scale.linear(),
      orient = "bottom",
      tickMajorSize = 6,
      tickMinorSize = 6,
      tickEndSize = 6,
      tickPadding = 3,
      tickArguments_ = [10],
      tickFormat_,
      tickSubdivide = 0;

  function axis(selection) {
    selection.each(function(d, i, j) {
      var g = d3.select(this);

      // Ticks.
      var ticks = scale.ticks.apply(scale, tickArguments_),
          tickFormat = tickFormat_ == null ? scale.tickFormat.apply(scale, tickArguments_) : tickFormat_;

      // Minor ticks.
      var subticks = d3_svg_axisSubdivide(scale, ticks, tickSubdivide),
          subtick = g.selectAll(".minor").data(subticks, String),
          subtickEnter = subtick.enter().insert("svg:line", "g").attr("class", "tick minor").style("opacity", 1e-6),
          subtickExit = transition(subtick.exit()).style("opacity", 1e-6).remove(),
          subtickUpdate = transition(subtick).style("opacity", 1);

      // Major ticks.
      var tick = g.selectAll("g").data(ticks, String),
          tickEnter = tick.enter().insert("svg:g", "path").style("opacity", 1e-6),
          tickExit = transition(tick.exit()).style("opacity", 1e-6).remove(),
          tickUpdate = transition(tick).style("opacity", 1),
          tickTransform;

      // Domain.
      var range = d3_scaleExtent(scale.range()),
          path = g.selectAll(".domain").data([0]),
          pathEnter = path.enter().append("svg:path").attr("class", "domain"),
          pathUpdate = transition(path);

      // Stash the new scale and grab the old scale.
      var scale0 = this.__chart__ || scale;
      this.__chart__ = scale.copy();

      tickEnter.append("svg:line").attr("class", "tick");
      tickEnter.append("svg:text");
      tickUpdate.select("text").text(tickFormat);

      switch (orient) {
        case "bottom": {
          tickTransform = d3_svg_axisX;
          subtickUpdate.attr("y2", tickMinorSize);
          tickEnter.select("text").attr("dy", ".71em").attr("text-anchor", "middle");
          tickUpdate.select("line").attr("y2", tickMajorSize);
          tickUpdate.select("text").attr("y", Math.max(tickMajorSize, 0) + tickPadding);
          pathUpdate.attr("d", "M" + range[0] + "," + tickEndSize + "V0H" + range[1] + "V" + tickEndSize);
          break;
        }
        case "top": {
          tickTransform = d3_svg_axisX;
          subtickUpdate.attr("y2", -tickMinorSize);
          tickEnter.select("text").attr("text-anchor", "middle");
          tickUpdate.select("line").attr("y2", -tickMajorSize);
          tickUpdate.select("text").attr("y", -(Math.max(tickMajorSize, 0) + tickPadding));
          pathUpdate.attr("d", "M" + range[0] + "," + -tickEndSize + "V0H" + range[1] + "V" + -tickEndSize);
          break;
        }
        case "left": {
          tickTransform = d3_svg_axisY;
          subtickUpdate.attr("x2", -tickMinorSize);
          tickEnter.select("text").attr("dy", ".32em").attr("text-anchor", "end");
          tickUpdate.select("line").attr("x2", -tickMajorSize);
          tickUpdate.select("text").attr("x", -(Math.max(tickMajorSize, 0) + tickPadding));
          pathUpdate.attr("d", "M" + -tickEndSize + "," + range[0] + "H0V" + range[1] + "H" + -tickEndSize);
          break;
        }
        case "right": {
          tickTransform = d3_svg_axisY;
          subtickUpdate.attr("x2", tickMinorSize);
          tickEnter.select("text").attr("dy", ".32em");
          tickUpdate.select("line").attr("x2", tickMajorSize);
          tickUpdate.select("text").attr("x", Math.max(tickMajorSize, 0) + tickPadding);
          pathUpdate.attr("d", "M" + tickEndSize + "," + range[0] + "H0V" + range[1] + "H" + tickEndSize);
          break;
        }
      }

      tickEnter.call(tickTransform, scale0);
      tickUpdate.call(tickTransform, scale);
      tickExit.call(tickTransform, scale);

      subtickEnter.call(tickTransform, scale0);
      subtickUpdate.call(tickTransform, scale);
      subtickExit.call(tickTransform, scale);

      function transition(o) {
        return selection.delay ? o.transition()
            .delay(selection[j][i].delay)
            .duration(selection[j][i].duration)
            .ease(selection.ease()) : o;
      }
    });
  }

  axis.scale = function(x) {
    if (!arguments.length) return scale;
    scale = x;
    return axis;
  };

  axis.orient = function(x) {
    if (!arguments.length) return orient;
    orient = x;
    return axis;
  };

  axis.ticks = function() {
    if (!arguments.length) return tickArguments_;
    tickArguments_ = arguments;
    return axis;
  };

  axis.tickFormat = function(x) {
    if (!arguments.length) return tickFormat_;
    tickFormat_ = x;
    return axis;
  };

  axis.tickSize = function(x, y, z) {
    if (!arguments.length) return tickMajorSize;
    var n = arguments.length - 1;
    tickMajorSize = +x;
    tickMinorSize = n > 1 ? +y : tickMajorSize;
    tickEndSize = n > 0 ? +arguments[n] : tickMajorSize;
    return axis;
  };

  axis.tickPadding = function(x) {
    if (!arguments.length) return tickPadding;
    tickPadding = +x;
    return axis;
  };

  axis.tickSubdivide = function(x) {
    if (!arguments.length) return tickSubdivide;
    tickSubdivide = +x;
    return axis;
  };

  return axis;
};

function d3_svg_axisX(selection, x) {
  selection.attr("transform", function(d) { return "translate(" + x(d) + ",0)"; });
}

function d3_svg_axisY(selection, y) {
  selection.attr("transform", function(d) { return "translate(0," + y(d) + ")"; });
}

function d3_svg_axisSubdivide(scale, ticks, m) {
  subticks = [];
  if (m && ticks.length > 1) {
    var extent = d3_scaleExtent(scale.domain()),
        subticks,
        i = -1,
        n = ticks.length,
        d = (ticks[1] - ticks[0]) / ++m,
        j,
        v;
    while (++i < n) {
      for (j = m; --j > 0;) {
        if ((v = +ticks[i] - j * d) >= extent[0]) {
          subticks.push(v);
        }
      }
    }
    for (--i, j = 0; ++j < m && (v = +ticks[i] + j * d) < extent[1];) {
      subticks.push(v);
    }
  }
  return subticks;
}
d3.behavior = {};
d3.behavior.drag = function() {
  var event = d3.dispatch("drag", "dragstart", "dragend");

  function drag() {
    this
        .on("mousedown.drag", mousedown)
        .on("touchstart.drag", mousedown);

    d3.select(window)
        .on("mousemove.drag", d3_behavior_dragMove)
        .on("touchmove.drag", d3_behavior_dragMove)
        .on("mouseup.drag", d3_behavior_dragUp, true)
        .on("touchend.drag", d3_behavior_dragUp, true)
        .on("click.drag", d3_behavior_dragClick, true);
  }

  // snapshot the local context for subsequent dispatch
  function start() {
    d3_behavior_dragEvent = event;
    d3_behavior_dragOffset = d3_behavior_dragPoint((d3_behavior_dragTarget = this).parentNode);
    d3_behavior_dragMoved = 0;
    d3_behavior_dragArguments = arguments;
  }

  function mousedown() {
    start.apply(this, arguments);
    d3_behavior_dragDispatch("dragstart");
  }

  drag.on = function(type, listener) {
    event[type].add(listener);
    return drag;
  };

  return drag;
};

var d3_behavior_dragEvent,
    d3_behavior_dragTarget,
    d3_behavior_dragArguments,
    d3_behavior_dragOffset,
    d3_behavior_dragMoved,
    d3_behavior_dragStopClick;

function d3_behavior_dragDispatch(type) {
  var o = d3.event, p = d3_behavior_dragTarget.parentNode, dx = 0, dy = 0;

  if (p) {
    p = d3_behavior_dragPoint(p);
    dx = p[0] - d3_behavior_dragOffset[0];
    dy = p[1] - d3_behavior_dragOffset[1];
    d3_behavior_dragOffset = p;
    d3_behavior_dragMoved |= dx | dy;
  }

  try {
    d3.event = {dx: dx, dy: dy};
    d3_behavior_dragEvent[type].dispatch.apply(d3_behavior_dragTarget, d3_behavior_dragArguments);
  } finally {
    d3.event = o;
  }

  o.preventDefault();
}

function d3_behavior_dragPoint(container) {
  return d3.event.touches
      ? d3.svg.touches(container)[0]
      : d3.svg.mouse(container);
}

function d3_behavior_dragMove() {
  if (!d3_behavior_dragTarget) return;
  var parent = d3_behavior_dragTarget.parentNode;

  // O NOES! The drag element was removed from the DOM.
  if (!parent) return d3_behavior_dragUp();

  d3_behavior_dragDispatch("drag");
  d3_behavior_dragCancel();
}

function d3_behavior_dragUp() {
  if (!d3_behavior_dragTarget) return;
  d3_behavior_dragDispatch("dragend");
  d3_behavior_dragTarget = null;

  // If the node was moved, prevent the mouseup from propagating.
  // Also prevent the subsequent click from propagating (e.g., for anchors).
  if (d3_behavior_dragMoved) {
    d3_behavior_dragStopClick = true;
    d3_behavior_dragCancel();
  }
}

function d3_behavior_dragClick() {
  if (d3_behavior_dragStopClick) {
    d3_behavior_dragCancel();
    d3_behavior_dragStopClick = false;
  }
}

function d3_behavior_dragCancel() {
  d3.event.stopPropagation();
  d3.event.preventDefault();
}
// TODO unbind zoom behavior?
// TODO unbind listener?
d3.behavior.zoom = function() {
  var xyz = [0, 0, 0],
      event = d3.dispatch("zoom");

  function zoom() {
    this
        .on("mousedown.zoom", mousedown)
        .on("mousewheel.zoom", mousewheel)
        .on("DOMMouseScroll.zoom", mousewheel)
        .on("dblclick.zoom", dblclick)
        .on("touchstart.zoom", touchstart);

    d3.select(window)
        .on("mousemove.zoom", d3_behavior_zoomMousemove)
        .on("mouseup.zoom", d3_behavior_zoomMouseup)
        .on("touchmove.zoom", d3_behavior_zoomTouchmove)
        .on("touchend.zoom", d3_behavior_zoomTouchup)
        .on("click.zoom", d3_behavior_zoomClick, true);
  }

  // snapshot the local context for subsequent dispatch
  function start() {
    d3_behavior_zoomXyz = xyz;
    d3_behavior_zoomDispatch = event.zoom.dispatch;
    d3_behavior_zoomTarget = this;
    d3_behavior_zoomArguments = arguments;
  }

  function mousedown() {
    start.apply(this, arguments);
    d3_behavior_zoomPanning = d3_behavior_zoomLocation(d3.svg.mouse(d3_behavior_zoomTarget));
    d3_behavior_zoomMoved = false;
    d3.event.preventDefault();
    window.focus();
  }

  // store starting mouse location
  function mousewheel() {
    start.apply(this, arguments);
    if (!d3_behavior_zoomZooming) d3_behavior_zoomZooming = d3_behavior_zoomLocation(d3.svg.mouse(d3_behavior_zoomTarget));
    d3_behavior_zoomTo(d3_behavior_zoomDelta() + xyz[2], d3.svg.mouse(d3_behavior_zoomTarget), d3_behavior_zoomZooming);
  }

  function dblclick() {
    start.apply(this, arguments);
    var mouse = d3.svg.mouse(d3_behavior_zoomTarget);
    d3_behavior_zoomTo(d3.event.shiftKey ? Math.ceil(xyz[2] - 1) : Math.floor(xyz[2] + 1), mouse, d3_behavior_zoomLocation(mouse));
  }

  // doubletap detection
  function touchstart() {
    start.apply(this, arguments);
    var touches = d3_behavior_zoomTouchup(),
        touch,
        now = Date.now();
    if ((touches.length === 1) && (now - d3_behavior_zoomLast < 300)) {
      d3_behavior_zoomTo(1 + Math.floor(xyz[2]), touch = touches[0], d3_behavior_zoomLocations[touch.identifier]);
    }
    d3_behavior_zoomLast = now;
  }

  zoom.on = function(type, listener) {
    event[type].add(listener);
    return zoom;
  };

  return zoom;
};

var d3_behavior_zoomDiv,
    d3_behavior_zoomPanning,
    d3_behavior_zoomZooming,
    d3_behavior_zoomLocations = {}, // identifier -> location
    d3_behavior_zoomLast = 0,
    d3_behavior_zoomXyz,
    d3_behavior_zoomDispatch,
    d3_behavior_zoomTarget,
    d3_behavior_zoomArguments,
    d3_behavior_zoomMoved,
    d3_behavior_zoomStopClick;

function d3_behavior_zoomLocation(point) {
  return [
    point[0] - d3_behavior_zoomXyz[0],
    point[1] - d3_behavior_zoomXyz[1],
    d3_behavior_zoomXyz[2]
  ];
}

// detect the pixels that would be scrolled by this wheel event
function d3_behavior_zoomDelta() {

  // mousewheel events are totally broken!
  // https://bugs.webkit.org/show_bug.cgi?id=40441
  // not only that, but Chrome and Safari differ in re. to acceleration!
  if (!d3_behavior_zoomDiv) {
    d3_behavior_zoomDiv = d3.select("body").append("div")
        .style("visibility", "hidden")
        .style("top", 0)
        .style("height", 0)
        .style("width", 0)
        .style("overflow-y", "scroll")
      .append("div")
        .style("height", "2000px")
      .node().parentNode;
  }

  var e = d3.event, delta;
  try {
    d3_behavior_zoomDiv.scrollTop = 1000;
    d3_behavior_zoomDiv.dispatchEvent(e);
    delta = 1000 - d3_behavior_zoomDiv.scrollTop;
  } catch (error) {
    delta = e.wheelDelta || (-e.detail * 5);
  }

  return delta * .005;
}

// Note: Since we don't rotate, it's possible for the touches to become
// slightly detached from their original positions. Thus, we recompute the
// touch points on touchend as well as touchstart!
function d3_behavior_zoomTouchup() {
  var touches = d3.svg.touches(d3_behavior_zoomTarget),
      i = -1,
      n = touches.length,
      touch;
  while (++i < n) d3_behavior_zoomLocations[(touch = touches[i]).identifier] = d3_behavior_zoomLocation(touch);
  return touches;
}

function d3_behavior_zoomTouchmove() {
  var touches = d3.svg.touches(d3_behavior_zoomTarget);
  switch (touches.length) {

    // single-touch pan
    case 1: {
      var touch = touches[0];
      d3_behavior_zoomTo(d3_behavior_zoomXyz[2], touch, d3_behavior_zoomLocations[touch.identifier]);
      break;
    }

    // double-touch pan + zoom
    case 2: {
      var p0 = touches[0],
          p1 = touches[1],
          p2 = [(p0[0] + p1[0]) / 2, (p0[1] + p1[1]) / 2],
          l0 = d3_behavior_zoomLocations[p0.identifier],
          l1 = d3_behavior_zoomLocations[p1.identifier],
          l2 = [(l0[0] + l1[0]) / 2, (l0[1] + l1[1]) / 2, l0[2]];
      d3_behavior_zoomTo(Math.log(d3.event.scale) / Math.LN2 + l0[2], p2, l2);
      break;
    }
  }
}

function d3_behavior_zoomMousemove() {
  d3_behavior_zoomZooming = null;
  if (d3_behavior_zoomPanning) {
    d3_behavior_zoomMoved = true;
    d3_behavior_zoomTo(d3_behavior_zoomXyz[2], d3.svg.mouse(d3_behavior_zoomTarget), d3_behavior_zoomPanning);
  }
}

function d3_behavior_zoomMouseup() {
  if (d3_behavior_zoomPanning) {
    if (d3_behavior_zoomMoved) d3_behavior_zoomStopClick = true;
    d3_behavior_zoomMousemove();
    d3_behavior_zoomPanning = null;
  }
}

function d3_behavior_zoomClick() {
  if (d3_behavior_zoomStopClick) {
    d3.event.stopPropagation();
    d3.event.preventDefault();
    d3_behavior_zoomStopClick = false;
  }
}

function d3_behavior_zoomTo(z, x0, x1) {
  var K = Math.pow(2, (d3_behavior_zoomXyz[2] = z) - x1[2]),
      x = d3_behavior_zoomXyz[0] = x0[0] - K * x1[0],
      y = d3_behavior_zoomXyz[1] = x0[1] - K * x1[1],
      o = d3.event, // Events can be reentrant (e.g., focus).
      k = Math.pow(2, z);

  d3.event = {
    scale: k,
    translate: [x, y],
    transform: function(sx, sy) {
      if (sx) transform(sx, x);
      if (sy) transform(sy, y);
    }
  };

  function transform(scale, o) {
    var domain = scale.__domain || (scale.__domain = scale.domain()),