# Source: src/pixi/display/SpriteBatch.js

    /**
     * @author Mat Groves http://matgroves.com/
     */

    /**
     * The SpriteBatch class is a really fast version of the DisplayObjectContainer
     * built solely for speed, so use when you need a lot of sprites or particles.
     * And it's extremely easy to use :

        var container = new PIXI.SpriteBatch();

        for(var i  = 0; i < 100; i++)
        {
            var sprite = new PIXI.Sprite.fromImage("myImage.png");
            container.addChild(sprite);
        }
     * And here you have a hundred sprites that will be renderer at the speed of light
     *
     * @class SpriteBatch
     * @constructor
     * @param texture {Texture}
     */
    PIXI.SpriteBatch = function(texture)
    {
        PIXI.DisplayObjectContainer.call( this);

        this.textureThing = texture;

        this.ready = false;
    };

    PIXI.SpriteBatch.prototype = Object.create(PIXI.DisplayObjectContainer.prototype);
    PIXI.SpriteBatch.prototype.constructor = PIXI.SpriteBatch;

    /*
     * Initialises the spriteBatch
     *
     * @method initWebGL
     * @param gl {WebGLContext} the current WebGL drawing context
     */
    PIXI.SpriteBatch.prototype.initWebGL = function(gl)
    {
        // TODO only one needed for the whole engine really?
        this.fastSpriteBatch = new PIXI.WebGLFastSpriteBatch(gl);

        this.ready = true;
    };

    /*
     * Updates the object transform for rendering
     *
     * @method updateTransform
     * @private
     */
    PIXI.SpriteBatch.prototype.updateTransform = function()
    {
        // TODO don't need to!
        this.displayObjectUpdateTransform();
        //  PIXI.DisplayObjectContainer.prototype.updateTransform.call( this );
    };

    /**
    * Renders the object using the WebGL renderer
    *
    * @method _renderWebGL
    * @param renderSession {RenderSession}
    * @private
    */
    PIXI.SpriteBatch.prototype._renderWebGL = function(renderSession)
    {
        if (!this.visible || this.alpha <= 0 || !this.children.length) return;

        if (!this.ready)
        {
            this.initWebGL(renderSession.gl);
        }

        if (this.fastSpriteBatch.gl !== renderSession.gl)
        {
            this.fastSpriteBatch.setContext(renderSession.gl);
        }

        renderSession.spriteBatch.stop();

        renderSession.shaderManager.setShader(renderSession.shaderManager.fastShader);

        this.fastSpriteBatch.begin(this, renderSession);
        this.fastSpriteBatch.render(this);

        renderSession.spriteBatch.start();

    };

    /**
    * Renders the object using the Canvas renderer
    *
    * @method _renderCanvas
    * @param renderSession {RenderSession}
    * @private
    */
    PIXI.SpriteBatch.prototype._renderCanvas = function(renderSession)
    {
        if (!this.visible || this.alpha <= 0 || !this.children.length) return;

        var context = renderSession.context;

        context.globalAlpha = this.worldAlpha;

        this.displayObjectUpdateTransform();

        var transform = this.worldTransform;

        var isRotated = true;

        for (var i = 0; i < this.children.length; i++)
        {
            var child = this.children[i];

            if (!child.visible) continue;

            var texture = child.texture;
            var frame = texture.frame;

            context.globalAlpha = this.worldAlpha * child.alpha;

            if (child.rotation % (Math.PI * 2) === 0)
            {
                if (isRotated)
                {
                    context.setTransform(transform.a, transform.b, transform.c, transform.d, transform.tx, transform.ty);
                    isRotated = false;
                }

                // this is the fastest  way to optimise! - if rotation is 0 then we can avoid any kind of setTransform call
                context.drawImage(texture.baseTexture.source,
                                     frame.x,
                                     frame.y,
                                     frame.width,
                                     frame.height,
                                     ((child.anchor.x) * (-frame.width * child.scale.x) + child.position.x + 0.5 + renderSession.shakeX) | 0,
                                     ((child.anchor.y) * (-frame.height * child.scale.y) + child.position.y + 0.5 + renderSession.shakeY) | 0,
                                     frame.width * child.scale.x,
                                     frame.height * child.scale.y);
            }
            else
            {
                if (!isRotated) isRotated = true;

                child.displayObjectUpdateTransform();

                var childTransform = child.worldTransform;
                var tx = (childTransform.tx * renderSession.resolution) + renderSession.shakeX;
                var ty = (childTransform.ty * renderSession.resolution) + renderSession.shakeY;

                // allow for trimming

                if (renderSession.roundPixels)
                {
                    context.setTransform(childTransform.a, childTransform.b, childTransform.c, childTransform.d, tx | 0, ty | 0);
                }
                else
                {
                    context.setTransform(childTransform.a, childTransform.b, childTransform.c, childTransform.d, tx, ty);
                }

                context.drawImage(texture.baseTexture.source,
                                     frame.x,
                                     frame.y,
                                     frame.width,
                                     frame.height,
                                     ((child.anchor.x) * (-frame.width) + 0.5) | 0,
                                     ((child.anchor.y) * (-frame.height) + 0.5) | 0,
                                     frame.width,
                                     frame.height);
            }
        }

    };