Phaser Source: src/pixi/utils/CanvasPool.js

# Source: src/pixi/utils/CanvasPool.js

    /**
    * @author       Richard Davey <rich@photonstorm.com>
    * @copyright    2016 Photon Storm Ltd.
    * @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
    */

    /**
    * The CanvasPool is a global static object that allows Pixi and Phaser to pool canvas DOM elements.
    *
    * @class CanvasPool
    * @static
    */
    PIXI.CanvasPool = {

        /**
        * Creates a new Canvas DOM element, or pulls one from the pool if free.
        *
        * @method create
        * @static
        * @param parent {any} The parent of the canvas element.
        * @param width {number} The width of the canvas element.
        * @param height {number} The height of the canvas element.
        * @return {HTMLCanvasElement} The canvas element.
        */
        create: function (parent, width, height) {

            var idx = PIXI.CanvasPool.getFirst();
            var canvas;

            if (idx === -1)
            {
                var container = {
                    parent: parent,
                    canvas: document.createElement('canvas')
                }

                PIXI.CanvasPool.pool.push(container);

                canvas = container.canvas;
            }
            else
            {
                PIXI.CanvasPool.pool[idx].parent = parent;

                canvas = PIXI.CanvasPool.pool[idx].canvas;
            }

            if (width !== undefined)
            {
                canvas.width = width;
                canvas.height = height;
            }

            return canvas;

        },

        /**
        * Gets the first free canvas index from the pool.
        *
        * @method getFirst
        * @static
        * @return {number}
        */
        getFirst: function () {

            var pool = PIXI.CanvasPool.pool;

            for (var i = 0; i < pool.length; i++)
            {
                if (!pool[i].parent)
                {
                    return i;
                }
            }

            return -1;

        },

        /**
        * Removes the parent from a canvas element from the pool, freeing it up for re-use.
        *
        * @method remove
        * @param parent {any} The parent of the canvas element.
        * @static
        */
        remove: function (parent) {

            var pool = PIXI.CanvasPool.pool;

            for (var i = 0; i < pool.length; i++)
            {
                if (pool[i].parent === parent)
                {
                    pool[i].parent = null;
                    pool[i].canvas.width = 1;
                    pool[i].canvas.height = 1;
                }
            }

        },

        /**
        * Removes the parent from a canvas element from the pool, freeing it up for re-use.
        *
        * @method removeByCanvas
        * @param canvas {HTMLCanvasElement} The canvas element to remove
        * @static
        */
        removeByCanvas: function (canvas) {

            var pool = PIXI.CanvasPool.pool;

            for (var i = 0; i < pool.length; i++)
            {
                if (pool[i].canvas === canvas)
                {
                    pool[i].parent = null;
                    pool[i].canvas.width = 1;
                    pool[i].canvas.height = 1;
                }
            }

        },

        /**
        * Gets the total number of used canvas elements in the pool.
        *
        * @method getTotal
        * @static
        * @return {number} The number of in-use (parented) canvas elements in the pool.
        */
        getTotal: function () {

            var pool = PIXI.CanvasPool.pool;
            var c = 0;

            for (var i = 0; i < pool.length; i++)
            {
                if (pool[i].parent)
                {
                    c++;
                }
            }

            return c;

        },

        /**
        * Gets the total number of free canvas elements in the pool.
        *
        * @method getFree
        * @static
        * @return {number} The number of free (un-parented) canvas elements in the pool.
        */
        getFree: function () {

            var pool = PIXI.CanvasPool.pool;
            var c = 0;

            for (var i = 0; i < pool.length; i++)
            {
                if (!pool[i].parent)
                {
                    c++;
                }
            }

            return c;

        }

    };

    /**
     * The pool into which the canvas dom elements are placed.
     *
     * @property pool
     * @type Array
     * @static
     */
    PIXI.CanvasPool.pool = [];