phaser/src/geom/Circle.js

/**
* @author       Richard Davey <rich@photonstorm.com>
* @copyright    2013 Photon Storm Ltd.
* @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
*/

/**
* Creates a new Circle object with the center coordinate specified by the x and y parameters and the diameter specified by the diameter parameter. If you call this function without parameters, a circle with x, y, diameter and radius properties set to 0 is created.
* @class Circle
* @classdesc Phaser - Circle
* @constructor
* @param {number} [x] The x coordinate of the center of the circle.
* @param {number} [y] The y coordinate of the center of the circle.
* @param {number} [diameter] The diameter of the circle.
* @return {Phaser.Circle} This circle object
*/
Phaser.Circle = function (x, y, diameter) {

    x = x || 0;
    y = y || 0;
    diameter = diameter || 0;

    /**
    * @property {number} x - The x coordinate of the center of the circle.
    */
    this.x = x;

    /**
    * @property {number} y - The y coordinate of the center of the circle.
    */
    this.y = y;

    /**
    * @property {number} _diameter - The diameter of the circle.
    * @private
    */
    this._diameter = diameter;

    if (diameter > 0)
    {
        /**
        * @property {number} _radius - The radius of the circle.
        * @private
        */
        this._radius = diameter * 0.5;
    }
    else
    {
        this._radius = 0;
    }

};

Phaser.Circle.prototype = {

    /**
    * The circumference of the circle.
    * @method Phaser.Circle#circumference
    * @return {number}
    */
    circumference: function () {
        return 2 * (Math.PI * this._radius);
    },

    /**
    * Sets the members of Circle to the specified values.
    * @method Phaser.Circle#setTo
    * @param {number} x - The x coordinate of the center of the circle.
    * @param {number} y - The y coordinate of the center of the circle.
    * @param {number} diameter - The diameter of the circle in pixels.
    * @return {Circle} This circle object.
    */
    setTo: function (x, y, diameter) {
        this.x = x;
        this.y = y;
        this._diameter = diameter;
        this._radius = diameter * 0.5;
        return this;
    },

    /**
    * Copies the x, y and diameter properties from any given object to this Circle.
    * @method Phaser.Circle#copyFrom
    * @param {any} source - The object to copy from.
    * @return {Circle} This Circle object.
    */
    copyFrom: function (source) {
        return this.setTo(source.x, source.y, source.diameter);
    },

    /**
    * Copies the x, y and diameter properties from this Circle to any given object.
    * @method Phaser.Circle#copyTo
    * @param {any} dest - The object to copy to.
    * @return {Object} This dest object.
    */
    copyTo: function(dest) {
        dest.x = this.x;
        dest.y = this.y;
        dest.diameter = this._diameter;
        return dest;
    },

    /**
    * Returns the distance from the center of the Circle object to the given object
    * (can be Circle, Point or anything with x/y properties)
    * @method Phaser.Circle#distance
    * @param {object} dest - The target object. Must have visible x and y properties that represent the center of the object.
    * @param {boolean} [round] - Round the distance to the nearest integer (default false).
    * @return {number} The distance between this Point object and the destination Point object.
    */
    distance: function (dest, round) {

        if (typeof round === "undefined") { round = false }

        if (round)
        {
            return Phaser.Math.distanceRound(this.x, this.y, dest.x, dest.y);
        }
        else
        {
            return Phaser.Math.distance(this.x, this.y, dest.x, dest.y);
        }

    },

    /**
    * Returns a new Circle object with the same values for the x, y, width, and height properties as this Circle object.
    * @method Phaser.Circle#clone
    * @param {Phaser.Circle} out - Optional Circle object. If given the values will be set into the object, otherwise a brand new Circle object will be created and returned.
    * @return {Phaser.Circle} The cloned Circle object.
    */
    clone: function(out) {

        if (typeof out === "undefined") { out = new Phaser.Circle(); }

        return out.setTo(this.x, this.y, this.diameter);

    },

    /**
    * Return true if the given x/y coordinates are within this Circle object.
    * @method Phaser.Circle#contains
    * @param {number} x - The X value of the coordinate to test.
    * @param {number} y - The Y value of the coordinate to test.
    * @return {boolean} True if the coordinates are within this circle, otherwise false.
    */
    contains: function (x, y) {
        return Phaser.Circle.contains(this, x, y);
    },

    /**
    * Returns a Point object containing the coordinates of a point on the circumference of the Circle based on the given angle.
    * @method Phaser.Circle#circumferencePoint
    * @param {number} angle - The angle in radians (unless asDegrees is true) to return the point from.
    * @param {boolean} asDegrees - Is the given angle in radians (false) or degrees (true)?
    * @param {Phaser.Point} [out] - An optional Point object to put the result in to. If none specified a new Point object will be created.
    * @return {Phaser.Point} The Point object holding the result.
    */
    circumferencePoint: function (angle, asDegrees, out) {
        return Phaser.Circle.circumferencePoint(this, angle, asDegrees, out);
    },

    /**
    * Adjusts the location of the Circle object, as determined by its center coordinate, by the specified amounts.
    * @method Phaser.Circle#offset
    * @param {number} dx - Moves the x value of the Circle object by this amount.
    * @param {number} dy - Moves the y value of the Circle object by this amount.
    * @return {Circle} This Circle object.
    */
    offset: function (dx, dy) {
        this.x += dx;
        this.y += dy;
        return this;
    },

    /**
    * Adjusts the location of the Circle object using a Point object as a parameter. This method is similar to the Circle.offset() method, except that it takes a Point object as a parameter.
    * @method Phaser.Circle#offsetPoint
    * @param {Point} point A Point object to use to offset this Circle object (or any valid object with exposed x and y properties).
    * @return {Circle} This Circle object.
    */
    offsetPoint: function (point) {
        return this.offset(point.x, point.y);
    },

    /**
    * Returns a string representation of this object.
    * @method Phaser.Circle#toString
    * @return {string} a string representation of the instance.
    */
    toString: function () {
        return "[{Phaser.Circle (x=" + this.x + " y=" + this.y + " diameter=" + this.diameter + " radius=" + this.radius + ")}]";
    }

};

/**
* The largest distance between any two points on the circle. The same as the radius * 2.
* @name Phaser.Circle#diameter
* @property {number} diameter - Gets or sets the diameter of the circle.
*/
Object.defineProperty(Phaser.Circle.prototype, "diameter", {

    get: function () {
        return this._diameter;
    },

    set: function (value) {
        if (value > 0) {
            this._diameter = value;
            this._radius = value * 0.5;
        }
    }

});

/**
* The length of a line extending from the center of the circle to any point on the circle itself. The same as half the diameter.
* @name Phaser.Circle#radius
* @property {number} radius - Gets or sets the radius of the circle.
*/
Object.defineProperty(Phaser.Circle.prototype, "radius", {
    
    get: function () {
        return this._radius;
    },

    set: function (value) {
        if (value > 0) {
            this._radius = value;
            this._diameter = value * 2;
        }
    }

});

/**
* The x coordinate of the leftmost point of the circle. Changing the left property of a Circle object has no effect on the x and y properties. However it does affect the diameter, whereas changing the x value does not affect the diameter property.
* @name Phaser.Circle#left
* @propety {number} left - Gets or sets the value of the leftmost point of the circle.
*/
Object.defineProperty(Phaser.Circle.prototype, "left", {
    
    get: function () {
        return this.x - this._radius;
    },

    set: function (value) {
        if (value > this.x) {
            this._radius = 0;
            this._diameter = 0;
        } else {
            this.radius = this.x - value;
        }
    }

});

/**
* The x coordinate of the rightmost point of the circle. Changing the right property of a Circle object has no effect on the x and y properties. However it does affect the diameter, whereas changing the x value does not affect the diameter property.
* @name Phaser.Circle#right
* @property {number} right - Gets or sets the value of the rightmost point of the circle.
*/
Object.defineProperty(Phaser.Circle.prototype, "right", {

    get: function () {
        return this.x + this._radius;
    },

    set: function (value) {
        if (value < this.x) {
            this._radius = 0;
            this._diameter = 0;
        } else {
            this.radius = value - this.x;
        }
    }

});

/**
* The sum of the y minus the radius property. Changing the top property of a Circle object has no effect on the x and y properties, but does change the diameter.
* @name Phaser.Circle#top
* @property {number} top - Gets or sets the top of the circle.
*/
Object.defineProperty(Phaser.Circle.prototype, "top", {

    get: function () {
        return this.y - this._radius;
    },
    
    set: function (value) {
        if (value > this.y) {
            this._radius = 0;
            this._diameter = 0;
        } else {
            this.radius = this.y - value;
        }
    }

});

/**
* The sum of the y and radius properties. Changing the bottom property of a Circle object has no effect on the x and y properties, but does change the diameter.
* @name Phaser.Circle#bottom
* @property {number} bottom - Gets or sets the bottom of the circle.
*/
Object.defineProperty(Phaser.Circle.prototype, "bottom", {

    get: function () {
        return this.y + this._radius;
    },

    set: function (value) {

        if (value < this.y) {
            this._radius = 0;
            this._diameter = 0;
        } else {
            this.radius = value - this.y;
        }
    }

});

/**
* The area of this Circle.
* @name Phaser.Circle#area
* @property {number} area - The area of this circle.
* @readonly
*/
Object.defineProperty(Phaser.Circle.prototype, "area", {

    get: function () {
        if (this._radius > 0) {
            return Math.PI * this._radius * this._radius;
        } else {
            return 0;
        }
    }

});

/**
* Determines whether or not this Circle object is empty. Will return a value of true if the Circle objects diameter is less than or equal to 0; otherwise false.
* If set to true it will reset all of the Circle objects properties to 0. A Circle object is empty if its diameter is less than or equal to 0.
* @name Phaser.Circle#empty
* @property {boolean} empty - Gets or sets the empty state of the circle.
*/
Object.defineProperty(Phaser.Circle.prototype, "empty", {

    get: function () {
        return (this._diameter === 0);
    },

    set: function (value) {

        if (value === true)
        {
            this.setTo(0, 0, 0);
        }

    }

});

/**
* Return true if the given x/y coordinates are within the Circle object.
* @method Phaser.Circle.contains
* @param {Phaser.Circle} a - The Circle to be checked.
* @param {number} x - The X value of the coordinate to test.
* @param {number} y - The Y value of the coordinate to test.
* @return {boolean} True if the coordinates are within this circle, otherwise false.
*/
Phaser.Circle.contains = function (a, x, y) {

    //  Check if x/y are within the bounds first
    if (x >= a.left && x <= a.right && y >= a.top && y <= a.bottom) {

        var dx = (a.x - x) * (a.x - x);
        var dy = (a.y - y) * (a.y - y);

        return (dx + dy) <= (a.radius * a.radius);

    }

    return false;

};

/**
* Determines whether the two Circle objects match. This method compares the x, y and diameter properties.
* @method Phaser.Circle.equals
* @param {Phaser.Circle} a - The first Circle object.
* @param {Phaser.Circle} b - The second Circle object.
* @return {boolean} A value of true if the object has exactly the same values for the x, y and diameter properties as this Circle object; otherwise false.
*/
Phaser.Circle.equals = function (a, b) {
    return (a.x == b.x && a.y == b.y && a.diameter == b.diameter);
};

/**
* Determines whether the two Circle objects intersect.
* This method checks the radius distances between the two Circle objects to see if they intersect.
* @method Phaser.Circle.intersects
* @param {Phaser.Circle} a - The first Circle object.
* @param {Phaser.Circle} b - The second Circle object.
* @return {boolean} A value of true if the specified object intersects with this Circle object; otherwise false.
*/
Phaser.Circle.intersects = function (a, b) {
    return (Phaser.Math.distance(a.x, a.y, b.x, b.y) <= (a.radius + b.radius));
};

/**
* Returns a Point object containing the coordinates of a point on the circumference of the Circle based on the given angle.
* @method Phaser.Circle.circumferencePoint
* @param {Phaser.Circle} a - The first Circle object.
* @param {number} angle - The angle in radians (unless asDegrees is true) to return the point from.
* @param {boolean} asDegrees - Is the given angle in radians (false) or degrees (true)?
* @param {Phaser.Point} [out] - An optional Point object to put the result in to. If none specified a new Point object will be created.
* @return {Phaser.Point} The Point object holding the result.
*/
Phaser.Circle.circumferencePoint = function (a, angle, asDegrees, out) {

    if (typeof asDegrees === "undefined") { asDegrees = false; }
    if (typeof out === "undefined") { out = new Phaser.Point(); }

    if (asDegrees === true) {
        angle = Phaser.Math.radToDeg(angle);
    }

    out.x = a.x + a.radius * Math.cos(angle);
    out.y = a.y + a.radius * Math.sin(angle);

    return out;

};

/**
* Checks if the given Circle and Rectangle objects intersect.
* @method Phaser.Circle.intersectsRectangle
* @param {Phaser.Circle} c - The Circle object to test.
* @param {Phaser.Rectangle} r - The Rectangle object to test.
* @return {boolean} True if the two objects intersect, otherwise false.
*/
Phaser.Circle.intersectsRectangle = function (c, r) {

    var cx = Math.abs(c.x - r.x - r.halfWidth);
    var xDist = r.halfWidth + c.radius;

    if (cx > xDist) {
        return false;
    }

    var cy = Math.abs(c.y - r.y - r.halfHeight);
    var yDist = r.halfHeight + c.radius;

    if (cy > yDist) {
        return false;
    }

    if (cx <= r.halfWidth || cy <= r.halfHeight) {
        return true;
    }

    var xCornerDist = cx - r.halfWidth;
    var yCornerDist = cy - r.halfHeight;
    var xCornerDistSq = xCornerDist * xCornerDist;
    var yCornerDistSq = yCornerDist * yCornerDist;
    var maxCornerDistSq = c.radius * c.radius;

    return xCornerDistSq + yCornerDistSq <= maxCornerDistSq;

};