tr = trail()
.x(d => d[0])
.y(d => d[1])
.size(d => d[2])
svg`<svg viewBox="0 0 500 210">
<path d="${tr.context(null)(data)}" fill="orange">
`
{
const scale = width / 500,
context = DOM.context2d(width, 210 * scale);
context.scale(scale, scale);
context.beginPath();
tr.context(context)(data);
context.fillStyle = "lightblue";
context.fill();
return context.canvas;
}
{
const scale = width / 500,
context = DOM.context2d(width, 210 * scale);
context.scale(scale, scale);
context.beginPath();
tr.context(context)(data);
context.stroke();
return context.canvas;
}
function constant(x) {
return () => x;
}
trail = function() {
const Tau = 2 * Math.PI,
path = d3.path;
var x = d => d[0],
y = d => d[1],
size = d => d[2],
defined = d => true,
context = null,
ready,
x1,
y1,
r1;
function point(x2, y2, w2) {
var r2 = w2 / 2;
if (ready) {
var ux = y1 - y2,
uy = x2 - x1;
if (ux || uy) {
// get normal vector
var ud = Math.sqrt(ux * ux + uy * uy),
rx = (ux /= ud) * r1,
ry = (uy /= ud) * r1,
t = Math.atan2(uy, ux);
// draw segment
context.moveTo(x1 - rx, y1 - ry);
context.lineTo(x2 - ux * r2, y2 - uy * r2);
context.arc(x2, y2, r2, t - Math.PI, t);
context.lineTo(x1 + rx, y1 + ry);
context.arc(x1, y1, r1, t, t + Math.PI);
} else {
context.arc(x2, y2, r2, 0, Tau);
}
context.closePath();
} else {
ready = 1;
}
x1 = x2;
y1 = y2;
r1 = r2;
}
function trail(data) {
var i,
n = data.length,
d,
def,
s,
defined0 = false,
buffer;
if (context == null) context = buffer = path();
for (i = 0; i < n; ++i) {
d = data[i];
def = defined(d, i, data) && (s = +size(d, i, data));
if (!(i < n && def) === defined0) {
if ((defined0 = !defined0)) ready = 0;
}
if (defined0) point(+x(d, i, data), +y(d, i, data), s);
}
if (buffer) {
context = null;
return buffer + '' || null;
}
}
trail.x = function(_) {
if (arguments.length) {
x = typeof _ === "function" ? _ : constant(+_);
return trail;
} else {
return x;
}
};
trail.y = function(_) {
if (arguments.length) {
y = typeof _ === "function" ? _ : constant(+_);
return trail;
} else {
return y;
}
};
trail.size = function(_) {
if (arguments.length) {
size = typeof _ === "function" ? _ : constant(+_);
return trail;
} else {
return size;
}
};
trail.defined = function(_) {
if (arguments.length) {
defined = _;
return trail;
} else {
return defined;
}
};
trail.context = function(_) {
if (arguments.length) {
if (_ == null) {
context = null;
} else {
context = _;
}
return trail;
} else {
return context;
}
};
return trail;
}
d3 = require("d3-path@2", "d3-shape@2")
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