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Controls/Paint/Math/Vector.js

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+////////////////////////////////////////////////////////////
+////   © Microsoft. All rights reserved.                ////
+////////////////////////////////////////////////////////////
+
+(function (AppNS) {
+    'use strict';
+
+    // The Vector class represents a position-less vector in 2-Dimensional space.
+    // A Vector has direction and length, both represented in the form of change in x and change in y.
+    var Vector = WinJS.Class.define(
+
+        // Constructor
+        function (x, y) {
+            this.x = x || 0; // The x-component of this vector
+            this.y = y || 0; // The y-component of this vector
+        },
+
+        // Variables and Functions
+        {
+            // The length of this vector, as calculated by it's x and y components
+            length: {
+                get: function () {
+                    return Math.sqrt(this.x * this.x + this.y * this.y);
+                },
+                set: function (length) {
+                    this.normalize();
+                    this.scale(length);
+                }
+            },
+
+            // Return the dot product of this vector and v
+            dot: function (vector) {
+                return this.x * vector.x + this.y * vector.y;
+            },
+
+            // Sets this vector to the given x and y
+            fromXY: function (x, y) {
+                this.x = x;
+                this.y = y;
+            },
+
+            // Set this vector to the given vector
+            fromVector: function (vector) {
+                this.x = vector.x;
+                this.y = vector.y;
+            },
+
+            // Create a vector from point1 pointing towards point2
+            fromPoints: function (point1, point2) {
+                this.x = point2.x - point1.x;
+                this.y = point2.y - point1.y;
+            },
+
+            // Rotates this vector by 90 degrees counter-clockwise, making it perpendicular to what it was
+            toPerp: function () {
+                var temp = this.x;
+                this.x = -1 * this.y
+                this.y = temp;
+            },
+
+            // Rotates this vector counter-clockwise by angle in radians
+            rotate: function (angle) {
+                var cos = Math.cos(angle);
+                var sin = Math.sin(angle);
+                var x = this.x;
+                var y = this.y;
+                this.x = x * cos - y * sin;
+                this.y = x * sin + y * cos;
+            },
+
+            // Scales this vector by a constant
+            scale: function (constant) {
+                this.x = this.x * constant;
+                this.y = this.y * constant;
+            },
+
+            // Returns the angle in radians between this vector and v
+            angle: function (vector) {
+                var l1 = this.length;
+                var l2 = vector.length;
+                if (l1 !== 0 && l2 !== 0) {
+                    var val = this.dot(vector) / (l1 * l2);
+                    val = val > 1.0 ? 1.0 : val;
+                    val = val < -1.0 ? -1.0 : val;
+                    return Math.acos(val);
+                }
+            },
+
+            // Returns the slope (dy/dx) of this vector
+            getSlope: function () {
+                return this.y / this.x;
+            },
+
+            // Normalizes (sets to length 1) this vector
+            normalize: function () {
+                var length = this.length;
+                if (length !== 0) {
+                    this.scale(1 / length);
+                }
+            },
+
+            // Sets this vector to the result of subtracting the given vector from this
+            sub: function (vector) {
+                this.x = this.x - vector.x;
+                this.y = this.y - vector.y;
+            },
+
+            // Sets this vector to the result of adding the given vector to this
+            add: function (vector) {
+                this.x = this.x + vector.x;
+                this.y = this.y + vector.y;
+            },
+
+            // Returns true if this vector is equal to another
+            equals: function (vector) {
+                return this.x === vector.x && this.y === vector.y;
+            },
+
+            // Returns a copy of this vector
+            copy: function () {
+                return new AppNS.Painter.Math.Vector(this.x, this.y);
+            },
+
+            // Projects this vector onto the given direction.
+            // Note: the length of the direction vector is irrelevant.
+            project: function (vector) {
+                var direction = vector.copy();
+                var length = this.componentIn(direction);
+                direction.length = length;
+                this.fromVector(direction);
+            },
+
+            // Returns the length of the component of this vector in the given vector's direction
+            componentIn: function (vector) {
+                return this.dot(vector) / vector.length;
+            }
+    });
+
+    WinJS.Namespace.defineWithParent(AppNS, "Painter.Math", {
+        Vector: Vector
+    });
+
+})(Microsoft.Paint);