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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);
}
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