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diff --git a/devtools/server/actors/utils/shapes-utils.js b/devtools/server/actors/utils/shapes-utils.js
new file mode 100644
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+++ b/devtools/server/actors/utils/shapes-utils.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Get the distance between two points on a plane.
+ * @param {Number} x1 the x coord of the first point
+ * @param {Number} y1 the y coord of the first point
+ * @param {Number} x2 the x coord of the second point
+ * @param {Number} y2 the y coord of the second point
+ * @returns {Number} the distance between the two points
+ */
+const getDistance = (x1, y1, x2, y2) => {
+  return Math.round(Math.hypot(x2 - x1, y2 - y1));
+};
+
+/**
+ * Determine if the given x/y coords are along the edge of the given ellipse.
+ * We allow for a small area around the edge that still counts as being on the edge.
+ * @param {Number} x the x coordinate of the click
+ * @param {Number} y the y coordinate of the click
+ * @param {Number} cx the x coordinate of the center of the ellipse
+ * @param {Number} cy the y coordinate of the center of the ellipse
+ * @param {Number} rx the x radius of the ellipse
+ * @param {Number} ry the y radius of the ellipse
+ * @param {Number} clickWidthX the width of the area that counts as being on the edge
+ *                             along the x radius.
+ * @param {Number} clickWidthY the width of the area that counts as being on the edge
+ *                             along the y radius.
+ * @returns {Boolean} whether the click counts as being on the edge of the ellipse.
+ */
+const clickedOnEllipseEdge = (
+  x,
+  y,
+  cx,
+  cy,
+  rx,
+  ry,
+  clickWidthX,
+  clickWidthY
+) => {
+  // The formula to determine if something is inside or on the edge of an ellipse is:
+  // (x - cx)^2/rx^2 + (y - cy)^2/ry^2 <= 1. If > 1, it's outside.
+  // We make two ellipses, adjusting rx and ry with clickWidthX and clickWidthY
+  // to allow for an area around the edge of the ellipse that can be clicked on.
+  // If the click was outside the inner ellipse and inside the outer ellipse, return true.
+  const inner =
+    (x - cx) ** 2 / (rx - clickWidthX) ** 2 +
+    (y - cy) ** 2 / (ry - clickWidthY) ** 2;
+  const outer =
+    (x - cx) ** 2 / (rx + clickWidthX) ** 2 +
+    (y - cy) ** 2 / (ry + clickWidthY) ** 2;
+  return inner >= 1 && outer <= 1;
+};
+
+/**
+ * Get the distance between a point and a line defined by two other points.
+ * @param {Number} x1 the x coordinate of the first point in the line
+ * @param {Number} y1 the y coordinate of the first point in the line
+ * @param {Number} x2 the x coordinate of the second point in the line
+ * @param {Number} y2 the y coordinate of the second point in the line
+ * @param {Number} x3 the x coordinate of the point for which the distance is found
+ * @param {Number} y3 the y coordinate of the point for which the distance is found
+ * @returns {Number} the distance between (x3,y3) and the line defined by
+ *          (x1,y1) and (y1,y2)
+ */
+const distanceToLine = (x1, y1, x2, y2, x3, y3) => {
+  // https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line#Line_defined_by_two_points
+  const num = Math.abs((y2 - y1) * x3 - (x2 - x1) * y3 + x2 * y1 - y2 * x1);
+  const denom = getDistance(x1, y1, x2, y2);
+  return num / denom;
+};
+
+/**
+ * Get the point on the line defined by points a,b that is closest to point c
+ * @param {Number} ax the x coordinate of point a
+ * @param {Number} ay the y coordinate of point a
+ * @param {Number} bx the x coordinate of point b
+ * @param {Number} by the y coordinate of point b
+ * @param {Number} cx the x coordinate of point c
+ * @param {Number} cy the y coordinate of point c
+ * @returns {Array} a 2 element array that contains the x/y coords of the projected point
+ */
+const projection = (ax, ay, bx, by, cx, cy) => {
+  // https://en.wikipedia.org/wiki/Vector_projection#Vector_projection_2
+  const ab = [bx - ax, by - ay];
+  const ac = [cx - ax, cy - ay];
+  const scalar = dotProduct(ab, ac) / dotProduct(ab, ab);
+  return [ax + scalar * ab[0], ay + scalar * ab[1]];
+};
+
+/**
+ * Get the dot product of two vectors, represented by arrays of numbers.
+ * @param {Array} a the first vector
+ * @param {Array} b the second vector
+ * @returns {Number} the dot product of a and b
+ */
+const dotProduct = (a, b) => {
+  return a.reduce((prev, curr, i) => {
+    return prev + curr * b[i];
+  }, 0);
+};
+
+/**
+ * Determine if the given x/y coords are above the given point.
+ * @param {Number} x the x coordinate of the click
+ * @param {Number} y the y coordinate of the click
+ * @param {Number} pointX the x coordinate of the center of the point
+ * @param {Number} pointY the y coordinate of the center of the point
+ * @param {Number} radiusX the x radius of the point
+ * @param {Number} radiusY the y radius of the point
+ * @returns {Boolean} whether the click was on the point
+ */
+const clickedOnPoint = (x, y, pointX, pointY, radiusX, radiusY) => {
+  return (
+    x >= pointX - radiusX &&
+    x <= pointX + radiusX &&
+    y >= pointY - radiusY &&
+    y <= pointY + radiusY
+  );
+};
+
+const roundTo = (value, exp) => {
+  // If the exp is undefined or zero...
+  if (typeof exp === "undefined" || +exp === 0) {
+    return Math.round(value);
+  }
+  value = +value;
+  exp = +exp;
+  // If the value is not a number or the exp is not an integer...
+  if (isNaN(value) || !(typeof exp === "number" && exp % 1 === 0)) {
+    return NaN;
+  }
+  // Shift
+  value = value.toString().split("e");
+  value = Math.round(+(value[0] + "e" + (value[1] ? +value[1] - exp : -exp)));
+  // Shift back
+  value = value.toString().split("e");
+  return +(value[0] + "e" + (value[1] ? +value[1] + exp : exp));
+};
+
+exports.getDistance = getDistance;
+exports.clickedOnEllipseEdge = clickedOnEllipseEdge;
+exports.distanceToLine = distanceToLine;
+exports.projection = projection;
+exports.clickedOnPoint = clickedOnPoint;
+exports.roundTo = roundTo;