first commit

node_modules/d3-path/LICENSE

@@ -0,0 +1,13 @@
+Copyright 2015-2022 Mike Bostock
+
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted, provided that the above copyright notice
+and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.

node_modules/d3-path/README.md

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+# d3-path
+
+Say you have some code that draws to a 2D canvas:
+
+```js
+function drawCircle(context, radius) {
+  context.moveTo(radius, 0);
+  context.arc(0, 0, radius, 0, 2 * Math.PI);
+}
+```
+
+The d3-path module lets you take this exact code and additionally render to [SVG](http://www.w3.org/TR/SVG/paths.html). It works by [serializing](#path_toString) [CanvasPathMethods](http://www.w3.org/TR/2dcontext/#canvaspathmethods) calls to [SVG path data](http://www.w3.org/TR/SVG/paths.html#PathData). For example:
+
+```js
+const context = d3.path();
+drawCircle(context, 40);
+pathElement.setAttribute("d", context.toString());
+```
+
+Now code you write once can be used with both Canvas (for performance) and SVG (for convenience). For a practical example, see [d3-shape](https://github.com/d3/d3-shape).
+
+## Installing
+
+If you use npm, `npm install d3-path`. You can also download the [latest release on GitHub](https://github.com/d3/d3-path/releases/latest). In modern browsers, you can import d3-path from jsDelivr:
+
+```html
+<script type="module">
+
+import {path} from "https://cdn.jsdelivr.net/npm/d3-path@3/+esm";
+
+const p = path();
+p.moveTo(1, 2);
+p.lineTo(3, 4);
+p.closePath();
+
+</script>
+```
+
+For legacy environments, you can load d3-path’s UMD bundle from an npm-based CDN such as jsDelivr; a `d3` global is exported:
+
+```html
+<script src="https://cdn.jsdelivr.net/npm/d3-path@3"></script>
+<script>
+
+const path = d3.path();
+
+</script>
+```
+
+## API Reference
+
+<a name="path" href="#path">#</a> d3.<b>path</b>() · [Source](https://github.com/d3/d3-path/blob/master/src/path.js), [Examples](https://observablehq.com/@d3/d3-path)
+
+Constructs a new path serializer that implements [CanvasPathMethods](http://www.w3.org/TR/2dcontext/#canvaspathmethods).
+
+<a name="path_moveTo" href="#path_moveTo">#</a> <i>path</i>.<b>moveTo</b>(<i>x</i>, <i>y</i>)
+
+Move to the specified point ⟨*x*, *y*⟩. Equivalent to [*context*.moveTo](http://www.w3.org/TR/2dcontext/#dom-context-2d-moveto) and SVG’s [“moveto” command](http://www.w3.org/TR/SVG/paths.html#PathDataMovetoCommands).
+
+<a name="path_closePath" href="#path_closePath">#</a> <i>path</i>.<b>closePath</b>()
+
+Ends the current subpath and causes an automatic straight line to be drawn from the current point to the initial point of the current subpath. Equivalent to [*context*.closePath](http://www.w3.org/TR/2dcontext/#dom-context-2d-closepath) and SVG’s [“closepath” command](http://www.w3.org/TR/SVG/paths.html#PathDataClosePathCommand).
+
+<a name="path_lineTo" href="#path_lineTo">#</a> <i>path</i>.<b>lineTo</b>(<i>x</i>, <i>y</i>)
+
+Draws a straight line from the current point to the specified point ⟨*x*, *y*⟩. Equivalent to [*context*.lineTo](http://www.w3.org/TR/2dcontext/#dom-context-2d-lineto) and SVG’s [“lineto” command](http://www.w3.org/TR/SVG/paths.html#PathDataLinetoCommands).
+
+<a name="path_quadraticCurveTo" href="#path_quadraticCurveTo">#</a> <i>path</i>.<b>quadraticCurveTo</b>(<i>cpx</i>, <i>cpy</i>, <i>x</i>, <i>y</i>)
+
+Draws a quadratic Bézier segment from the current point to the specified point ⟨*x*, *y*⟩, with the specified control point ⟨*cpx*, *cpy*⟩. Equivalent to [*context*.quadraticCurveTo](http://www.w3.org/TR/2dcontext/#dom-context-2d-quadraticcurveto) and SVG’s [quadratic Bézier curve commands](http://www.w3.org/TR/SVG/paths.html#PathDataQuadraticBezierCommands).
+
+<a name="path_bezierCurveTo" href="#path_bezierCurveTo">#</a> <i>path</i>.<b>bezierCurveTo</b>(<i>cpx1</i>, <i>cpy1</i>, <i>cpx2</i>, <i>cpy2</i>, <i>x</i>, <i>y</i>)
+
+Draws a cubic Bézier segment from the current point to the specified point ⟨*x*, *y*⟩, with the specified control points ⟨*cpx1*, *cpy1*⟩ and ⟨*cpx2*, *cpy2*⟩. Equivalent to [*context*.bezierCurveTo](http://www.w3.org/TR/2dcontext/#dom-context-2d-beziercurveto) and SVG’s [cubic Bézier curve commands](http://www.w3.org/TR/SVG/paths.html#PathDataCubicBezierCommands).
+
+<a name="path_arcTo" href="#path_arcTo">#</a> <i>path</i>.<b>arcTo</b>(<i>x1</i>, <i>y1</i>, <i>x2</i>, <i>y2</i>, <i>radius</i>)
+
+Draws a circular arc segment with the specified *radius* that starts tangent to the line between the current point and the specified point ⟨*x1*, *y1*⟩ and ends tangent to the line between the specified points ⟨*x1*, *y1*⟩ and ⟨*x2*, *y2*⟩. If the first tangent point is not equal to the current point, a straight line is drawn between the current point and the first tangent point. Equivalent to [*context*.arcTo](http://www.w3.org/TR/2dcontext/#dom-context-2d-arcto) and uses SVG’s [elliptical arc curve commands](http://www.w3.org/TR/SVG/paths.html#PathDataEllipticalArcCommands).
+
+<a name="path_arc" href="#path_arc">#</a> <i>path</i>.<b>arc</b>(<i>x</i>, <i>y</i>, <i>radius</i>, <i>startAngle</i>, <i>endAngle</i>[, <i>anticlockwise</i>])
+
+Draws a circular arc segment with the specified center ⟨*x*, *y*⟩, *radius*, *startAngle* and *endAngle*. If *anticlockwise* is true, the arc is drawn in the anticlockwise direction; otherwise, it is drawn in the clockwise direction. If the current point is not equal to the starting point of the arc, a straight line is drawn from the current point to the start of the arc. Equivalent to [*context*.arc](http://www.w3.org/TR/2dcontext/#dom-context-2d-arc) and uses SVG’s [elliptical arc curve commands](http://www.w3.org/TR/SVG/paths.html#PathDataEllipticalArcCommands).
+
+<a name="path_rect" href="#path_rect">#</a> <i>path</i>.<b>rect</b>(<i>x</i>, <i>y</i>, <i>w</i>, <i>h</i>)
+
+Creates a new subpath containing just the four points ⟨*x*, *y*⟩, ⟨*x* + *w*, *y*⟩, ⟨*x* + *w*, *y* + *h*⟩, ⟨*x*, *y* + *h*⟩, with those four points connected by straight lines, and then marks the subpath as closed. Equivalent to [*context*.rect](http://www.w3.org/TR/2dcontext/#dom-context-2d-rect) and uses SVG’s [“lineto” commands](http://www.w3.org/TR/SVG/paths.html#PathDataLinetoCommands).
+
+<a name="path_toString" href="#path_toString">#</a> <i>path</i>.<b>toString</b>()
+
+Returns the string representation of this *path* according to SVG’s [path data specification](http://www.w3.org/TR/SVG/paths.html#PathData).
+
+<a name="pathRound" href="#pathRound">#</a> d3.<b>pathRound</b>(*digits* = 3) · [Source](https://github.com/d3/d3-path/blob/master/src/path.js), [Examples](https://observablehq.com/@d3/d3-path)
+
+Like [d3.path](#path), except limits the digits after the decimal to the specified number of *digits*.

node_modules/d3-path/dist/d3-path.js

@@ -0,0 +1,169 @@
+// https://d3js.org/d3-path/ v3.1.0 Copyright 2015-2022 Mike Bostock
+(function (global, factory) {
+typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
+typeof define === 'function' && define.amd ? define(['exports'], factory) :
+(global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.d3 = global.d3 || {}));
+})(this, (function (exports) { 'use strict';
+
+const pi = Math.PI,
+    tau = 2 * pi,
+    epsilon = 1e-6,
+    tauEpsilon = tau - epsilon;
+
+function append(strings) {
+  this._ += strings[0];
+  for (let i = 1, n = strings.length; i < n; ++i) {
+    this._ += arguments[i] + strings[i];
+  }
+}
+
+function appendRound(digits) {
+  let d = Math.floor(digits);
+  if (!(d >= 0)) throw new Error(`invalid digits: ${digits}`);
+  if (d > 15) return append;
+  const k = 10 ** d;
+  return function(strings) {
+    this._ += strings[0];
+    for (let i = 1, n = strings.length; i < n; ++i) {
+      this._ += Math.round(arguments[i] * k) / k + strings[i];
+    }
+  };
+}
+
+class Path {
+  constructor(digits) {
+    this._x0 = this._y0 = // start of current subpath
+    this._x1 = this._y1 = null; // end of current subpath
+    this._ = "";
+    this._append = digits == null ? append : appendRound(digits);
+  }
+  moveTo(x, y) {
+    this._append`M${this._x0 = this._x1 = +x},${this._y0 = this._y1 = +y}`;
+  }
+  closePath() {
+    if (this._x1 !== null) {
+      this._x1 = this._x0, this._y1 = this._y0;
+      this._append`Z`;
+    }
+  }
+  lineTo(x, y) {
+    this._append`L${this._x1 = +x},${this._y1 = +y}`;
+  }
+  quadraticCurveTo(x1, y1, x, y) {
+    this._append`Q${+x1},${+y1},${this._x1 = +x},${this._y1 = +y}`;
+  }
+  bezierCurveTo(x1, y1, x2, y2, x, y) {
+    this._append`C${+x1},${+y1},${+x2},${+y2},${this._x1 = +x},${this._y1 = +y}`;
+  }
+  arcTo(x1, y1, x2, y2, r) {
+    x1 = +x1, y1 = +y1, x2 = +x2, y2 = +y2, r = +r;
+
+    // Is the radius negative? Error.
+    if (r < 0) throw new Error(`negative radius: ${r}`);
+
+    let x0 = this._x1,
+        y0 = this._y1,
+        x21 = x2 - x1,
+        y21 = y2 - y1,
+        x01 = x0 - x1,
+        y01 = y0 - y1,
+        l01_2 = x01 * x01 + y01 * y01;
+
+    // Is this path empty? Move to (x1,y1).
+    if (this._x1 === null) {
+      this._append`M${this._x1 = x1},${this._y1 = y1}`;
+    }
+
+    // Or, is (x1,y1) coincident with (x0,y0)? Do nothing.
+    else if (!(l01_2 > epsilon));
+
+    // Or, are (x0,y0), (x1,y1) and (x2,y2) collinear?
+    // Equivalently, is (x1,y1) coincident with (x2,y2)?
+    // Or, is the radius zero? Line to (x1,y1).
+    else if (!(Math.abs(y01 * x21 - y21 * x01) > epsilon) || !r) {
+      this._append`L${this._x1 = x1},${this._y1 = y1}`;
+    }
+
+    // Otherwise, draw an arc!
+    else {
+      let x20 = x2 - x0,
+          y20 = y2 - y0,
+          l21_2 = x21 * x21 + y21 * y21,
+          l20_2 = x20 * x20 + y20 * y20,
+          l21 = Math.sqrt(l21_2),
+          l01 = Math.sqrt(l01_2),
+          l = r * Math.tan((pi - Math.acos((l21_2 + l01_2 - l20_2) / (2 * l21 * l01))) / 2),
+          t01 = l / l01,
+          t21 = l / l21;
+
+      // If the start tangent is not coincident with (x0,y0), line to.
+      if (Math.abs(t01 - 1) > epsilon) {
+        this._append`L${x1 + t01 * x01},${y1 + t01 * y01}`;
+      }
+
+      this._append`A${r},${r},0,0,${+(y01 * x20 > x01 * y20)},${this._x1 = x1 + t21 * x21},${this._y1 = y1 + t21 * y21}`;
+    }
+  }
+  arc(x, y, r, a0, a1, ccw) {
+    x = +x, y = +y, r = +r, ccw = !!ccw;
+
+    // Is the radius negative? Error.
+    if (r < 0) throw new Error(`negative radius: ${r}`);
+
+    let dx = r * Math.cos(a0),
+        dy = r * Math.sin(a0),
+        x0 = x + dx,
+        y0 = y + dy,
+        cw = 1 ^ ccw,
+        da = ccw ? a0 - a1 : a1 - a0;
+
+    // Is this path empty? Move to (x0,y0).
+    if (this._x1 === null) {
+      this._append`M${x0},${y0}`;
+    }
+
+    // Or, is (x0,y0) not coincident with the previous point? Line to (x0,y0).
+    else if (Math.abs(this._x1 - x0) > epsilon || Math.abs(this._y1 - y0) > epsilon) {
+      this._append`L${x0},${y0}`;
+    }
+
+    // Is this arc empty? We’re done.
+    if (!r) return;
+
+    // Does the angle go the wrong way? Flip the direction.
+    if (da < 0) da = da % tau + tau;
+
+    // Is this a complete circle? Draw two arcs to complete the circle.
+    if (da > tauEpsilon) {
+      this._append`A${r},${r},0,1,${cw},${x - dx},${y - dy}A${r},${r},0,1,${cw},${this._x1 = x0},${this._y1 = y0}`;
+    }
+
+    // Is this arc non-empty? Draw an arc!
+    else if (da > epsilon) {
+      this._append`A${r},${r},0,${+(da >= pi)},${cw},${this._x1 = x + r * Math.cos(a1)},${this._y1 = y + r * Math.sin(a1)}`;
+    }
+  }
+  rect(x, y, w, h) {
+    this._append`M${this._x0 = this._x1 = +x},${this._y0 = this._y1 = +y}h${w = +w}v${+h}h${-w}Z`;
+  }
+  toString() {
+    return this._;
+  }
+}
+
+function path() {
+  return new Path;
+}
+
+// Allow instanceof d3.path
+path.prototype = Path.prototype;
+
+function pathRound(digits = 3) {
+  return new Path(+digits);
+}
+
+exports.Path = Path;
+exports.path = path;
+exports.pathRound = pathRound;
+
+}));

node_modules/d3-path/dist/d3-path.min.js

@@ -0,0 +1,2 @@
+// https://d3js.org/d3-path/ v3.1.0 Copyright 2015-2022 Mike Bostock
+!function(t,i){"object"==typeof exports&&"undefined"!=typeof module?i(exports):"function"==typeof define&&define.amd?define(["exports"],i):i((t="undefined"!=typeof globalThis?globalThis:t||self).d3=t.d3||{})}(this,(function(t){"use strict";const i=Math.PI,s=2*i,h=1e-6,e=s-h;function n(t){this._+=t[0];for(let i=1,s=t.length;i<s;++i)this._+=arguments[i]+t[i]}class _{constructor(t){this._x0=this._y0=this._x1=this._y1=null,this._="",this._append=null==t?n:function(t){let i=Math.floor(t);if(!(i>=0))throw new Error(`invalid digits: ${t}`);if(i>15)return n;const s=10**i;return function(t){this._+=t[0];for(let i=1,h=t.length;i<h;++i)this._+=Math.round(arguments[i]*s)/s+t[i]}}(t)}moveTo(t,i){this._append`M${this._x0=this._x1=+t},${this._y0=this._y1=+i}`}closePath(){null!==this._x1&&(this._x1=this._x0,this._y1=this._y0,this._append`Z`)}lineTo(t,i){this._append`L${this._x1=+t},${this._y1=+i}`}quadraticCurveTo(t,i,s,h){this._append`Q${+t},${+i},${this._x1=+s},${this._y1=+h}`}bezierCurveTo(t,i,s,h,e,n){this._append`C${+t},${+i},${+s},${+h},${this._x1=+e},${this._y1=+n}`}arcTo(t,s,e,n,_){if(t=+t,s=+s,e=+e,n=+n,(_=+_)<0)throw new Error(`negative radius: ${_}`);let a=this._x1,$=this._y1,o=e-t,r=n-s,p=a-t,d=$-s,l=p*p+d*d;if(null===this._x1)this._append`M${this._x1=t},${this._y1=s}`;else if(l>h)if(Math.abs(d*o-r*p)>h&&_){let u=e-a,f=n-$,x=o*o+r*r,y=u*u+f*f,c=Math.sqrt(x),M=Math.sqrt(l),b=_*Math.tan((i-Math.acos((x+l-y)/(2*c*M)))/2),g=b/M,w=b/c;Math.abs(g-1)>h&&this._append`L${t+g*p},${s+g*d}`,this._append`A${_},${_},0,0,${+(d*u>p*f)},${this._x1=t+w*o},${this._y1=s+w*r}`}else this._append`L${this._x1=t},${this._y1=s}`;else;}arc(t,n,_,a,$,o){if(t=+t,n=+n,o=!!o,(_=+_)<0)throw new Error(`negative radius: ${_}`);let r=_*Math.cos(a),p=_*Math.sin(a),d=t+r,l=n+p,u=1^o,f=o?a-$:$-a;null===this._x1?this._append`M${d},${l}`:(Math.abs(this._x1-d)>h||Math.abs(this._y1-l)>h)&&this._append`L${d},${l}`,_&&(f<0&&(f=f%s+s),f>e?this._append`A${_},${_},0,1,${u},${t-r},${n-p}A${_},${_},0,1,${u},${this._x1=d},${this._y1=l}`:f>h&&this._append`A${_},${_},0,${+(f>=i)},${u},${this._x1=t+_*Math.cos($)},${this._y1=n+_*Math.sin($)}`)}rect(t,i,s,h){this._append`M${this._x0=this._x1=+t},${this._y0=this._y1=+i}h${s=+s}v${+h}h${-s}Z`}toString(){return this._}}function a(){return new _}a.prototype=_.prototype,t.Path=_,t.path=a,t.pathRound=function(t=3){return new _(+t)}}));

node_modules/d3-path/package.json

@@ -0,0 +1,54 @@
+{
+  "name": "d3-path",
+  "version": "3.1.0",
+  "description": "Serialize Canvas path commands to SVG.",
+  "homepage": "https://d3js.org/d3-path/",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/d3/d3-path.git"
+  },
+  "keywords": [
+    "d3",
+    "d3-module",
+    "canvas",
+    "path",
+    "svg",
+    "graphics",
+    "CanvasRenderingContext2D",
+    "CanvasPathMethods",
+    "Path2D"
+  ],
+  "license": "ISC",
+  "author": {
+    "name": "Mike Bostock",
+    "url": "http://bost.ocks.org/mike"
+  },
+  "type": "module",
+  "files": [
+    "dist/**/*.js",
+    "src/**/*.js"
+  ],
+  "module": "src/index.js",
+  "main": "src/index.js",
+  "jsdelivr": "dist/d3-path.min.js",
+  "unpkg": "dist/d3-path.min.js",
+  "exports": {
+    "umd": "./dist/d3-path.min.js",
+    "default": "./src/index.js"
+  },
+  "sideEffects": false,
+  "devDependencies": {
+    "eslint": "8",
+    "mocha": "10",
+    "rollup": "3",
+    "rollup-plugin-terser": "7"
+  },
+  "scripts": {
+    "test": "mocha 'test/**/*-test.js' && eslint src test",
+    "prepublishOnly": "rm -rf dist && yarn test && rollup -c",
+    "postpublish": "git push && git push --tags && cd ../d3.github.com && git pull && cp ../${npm_package_name}/dist/${npm_package_name}.js ${npm_package_name}.v${npm_package_version%%.*}.js && cp ../${npm_package_name}/dist/${npm_package_name}.min.js ${npm_package_name}.v${npm_package_version%%.*}.min.js && git add ${npm_package_name}.v${npm_package_version%%.*}.js ${npm_package_name}.v${npm_package_version%%.*}.min.js && git commit -m \"${npm_package_name} ${npm_package_version}\" && git push && cd -"
+  },
+  "engines": {
+    "node": ">=12"
+  }
+}

node_modules/d3-path/src/index.js

@@ -0,0 +1 @@
+export {Path, path, pathRound} from "./path.js";

node_modules/d3-path/src/path.js

@@ -0,0 +1,156 @@
+const pi = Math.PI,
+    tau = 2 * pi,
+    epsilon = 1e-6,
+    tauEpsilon = tau - epsilon;
+
+function append(strings) {
+  this._ += strings[0];
+  for (let i = 1, n = strings.length; i < n; ++i) {
+    this._ += arguments[i] + strings[i];
+  }
+}
+
+function appendRound(digits) {
+  let d = Math.floor(digits);
+  if (!(d >= 0)) throw new Error(`invalid digits: ${digits}`);
+  if (d > 15) return append;
+  const k = 10 ** d;
+  return function(strings) {
+    this._ += strings[0];
+    for (let i = 1, n = strings.length; i < n; ++i) {
+      this._ += Math.round(arguments[i] * k) / k + strings[i];
+    }
+  };
+}
+
+export class Path {
+  constructor(digits) {
+    this._x0 = this._y0 = // start of current subpath
+    this._x1 = this._y1 = null; // end of current subpath
+    this._ = "";
+    this._append = digits == null ? append : appendRound(digits);
+  }
+  moveTo(x, y) {
+    this._append`M${this._x0 = this._x1 = +x},${this._y0 = this._y1 = +y}`;
+  }
+  closePath() {
+    if (this._x1 !== null) {
+      this._x1 = this._x0, this._y1 = this._y0;
+      this._append`Z`;
+    }
+  }
+  lineTo(x, y) {
+    this._append`L${this._x1 = +x},${this._y1 = +y}`;
+  }
+  quadraticCurveTo(x1, y1, x, y) {
+    this._append`Q${+x1},${+y1},${this._x1 = +x},${this._y1 = +y}`;
+  }
+  bezierCurveTo(x1, y1, x2, y2, x, y) {
+    this._append`C${+x1},${+y1},${+x2},${+y2},${this._x1 = +x},${this._y1 = +y}`;
+  }
+  arcTo(x1, y1, x2, y2, r) {
+    x1 = +x1, y1 = +y1, x2 = +x2, y2 = +y2, r = +r;
+
+    // Is the radius negative? Error.
+    if (r < 0) throw new Error(`negative radius: ${r}`);
+
+    let x0 = this._x1,
+        y0 = this._y1,
+        x21 = x2 - x1,
+        y21 = y2 - y1,
+        x01 = x0 - x1,
+        y01 = y0 - y1,
+        l01_2 = x01 * x01 + y01 * y01;
+
+    // Is this path empty? Move to (x1,y1).
+    if (this._x1 === null) {
+      this._append`M${this._x1 = x1},${this._y1 = y1}`;
+    }
+
+    // Or, is (x1,y1) coincident with (x0,y0)? Do nothing.
+    else if (!(l01_2 > epsilon));
+
+    // Or, are (x0,y0), (x1,y1) and (x2,y2) collinear?
+    // Equivalently, is (x1,y1) coincident with (x2,y2)?
+    // Or, is the radius zero? Line to (x1,y1).
+    else if (!(Math.abs(y01 * x21 - y21 * x01) > epsilon) || !r) {
+      this._append`L${this._x1 = x1},${this._y1 = y1}`;
+    }
+
+    // Otherwise, draw an arc!
+    else {
+      let x20 = x2 - x0,
+          y20 = y2 - y0,
+          l21_2 = x21 * x21 + y21 * y21,
+          l20_2 = x20 * x20 + y20 * y20,
+          l21 = Math.sqrt(l21_2),
+          l01 = Math.sqrt(l01_2),
+          l = r * Math.tan((pi - Math.acos((l21_2 + l01_2 - l20_2) / (2 * l21 * l01))) / 2),
+          t01 = l / l01,
+          t21 = l / l21;
+
+      // If the start tangent is not coincident with (x0,y0), line to.
+      if (Math.abs(t01 - 1) > epsilon) {
+        this._append`L${x1 + t01 * x01},${y1 + t01 * y01}`;
+      }
+
+      this._append`A${r},${r},0,0,${+(y01 * x20 > x01 * y20)},${this._x1 = x1 + t21 * x21},${this._y1 = y1 + t21 * y21}`;
+    }
+  }
+  arc(x, y, r, a0, a1, ccw) {
+    x = +x, y = +y, r = +r, ccw = !!ccw;
+
+    // Is the radius negative? Error.
+    if (r < 0) throw new Error(`negative radius: ${r}`);
+
+    let dx = r * Math.cos(a0),
+        dy = r * Math.sin(a0),
+        x0 = x + dx,
+        y0 = y + dy,
+        cw = 1 ^ ccw,
+        da = ccw ? a0 - a1 : a1 - a0;
+
+    // Is this path empty? Move to (x0,y0).
+    if (this._x1 === null) {
+      this._append`M${x0},${y0}`;
+    }
+
+    // Or, is (x0,y0) not coincident with the previous point? Line to (x0,y0).
+    else if (Math.abs(this._x1 - x0) > epsilon || Math.abs(this._y1 - y0) > epsilon) {
+      this._append`L${x0},${y0}`;
+    }
+
+    // Is this arc empty? We’re done.
+    if (!r) return;
+
+    // Does the angle go the wrong way? Flip the direction.
+    if (da < 0) da = da % tau + tau;
+
+    // Is this a complete circle? Draw two arcs to complete the circle.
+    if (da > tauEpsilon) {
+      this._append`A${r},${r},0,1,${cw},${x - dx},${y - dy}A${r},${r},0,1,${cw},${this._x1 = x0},${this._y1 = y0}`;
+    }
+
+    // Is this arc non-empty? Draw an arc!
+    else if (da > epsilon) {
+      this._append`A${r},${r},0,${+(da >= pi)},${cw},${this._x1 = x + r * Math.cos(a1)},${this._y1 = y + r * Math.sin(a1)}`;
+    }
+  }
+  rect(x, y, w, h) {
+    this._append`M${this._x0 = this._x1 = +x},${this._y0 = this._y1 = +y}h${w = +w}v${+h}h${-w}Z`;
+  }
+  toString() {
+    return this._;
+  }
+}
+
+export function path() {
+  return new Path;
+}
+
+// Allow instanceof d3.path
+path.prototype = Path.prototype;
+
+export function pathRound(digits = 3) {
+  return new Path(+digits);
+}