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export default function(x, y) {
if (isNaN(x = +x) || isNaN(y = +y)) return this; // ignore invalid points
var x0 = this._x0,
y0 = this._y0,
x1 = this._x1,
y1 = this._y1;
// If the quadtree has no extent, initialize them.
// Integer extent are necessary so that if we later double the extent,
// the existing quadrant boundaries don’t change due to floating point error!
if (isNaN(x0)) {
x1 = (x0 = Math.floor(x)) + 1;
y1 = (y0 = Math.floor(y)) + 1;
}
// Otherwise, double repeatedly to cover.
else {
var z = x1 - x0 || 1,
node = this._root,
parent,
i;
while (x0 > x || x >= x1 || y0 > y || y >= y1) {
i = (y < y0) << 1 | (x < x0);
parent = new Array(4), parent[i] = node, node = parent, z *= 2;
switch (i) {
case 0: x1 = x0 + z, y1 = y0 + z; break;
case 1: x0 = x1 - z, y1 = y0 + z; break;
case 2: x1 = x0 + z, y0 = y1 - z; break;
case 3: x0 = x1 - z, y0 = y1 - z; break;
}
}
if (this._root && this._root.length) this._root = node;
}
this._x0 = x0;
this._y0 = y0;
this._x1 = x1;
this._y1 = y1;
return this;
}
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