Source: core/renderers/webgl/managers/ShaderManager.js

var WebGLManager = require('./WebGLManager'),
    TextureShader = require('../shaders/TextureShader'),
    ComplexPrimitiveShader = require('../shaders/ComplexPrimitiveShader'),
    PrimitiveShader = require('../shaders/PrimitiveShader'),
    utils = require('../../../utils');

/**
 * @class
 * @memberof PIXI
 * @extends PIXI.WebGLManager
 * @param renderer {PIXI.WebGLRenderer} The renderer this manager works for.
 */
function ShaderManager(renderer)
{
    WebGLManager.call(this, renderer);

    /**
     * @member {number}
     */
    this.maxAttibs = 10;

    /**
     * @member {any[]}
     */
    this.attribState = [];

    /**
     * @member {any[]}
     */
    this.tempAttribState = [];

    for (var i = 0; i < this.maxAttibs; i++)
    {
        this.attribState[i] = false;
    }

    /**
     * @member {any[]}
     */
    this.stack = [];

    /**
     * @member {number}
     * @private
     */
    this._currentId = -1;

    /**
     * @member {PIXI.Shader}
     * @private
     */
    this.currentShader = null;

//    this.initPlugins();
}

ShaderManager.prototype = Object.create(WebGLManager.prototype);
ShaderManager.prototype.constructor = ShaderManager;
utils.pluginTarget.mixin(ShaderManager);

module.exports = ShaderManager;

/**
 * Called when there is a WebGL context change.
 *
 */
ShaderManager.prototype.onContextChange = function ()
{
    this.initPlugins();

    var gl = this.renderer.gl;

    // get the maximum number of attribute correctly as this tends to vary
    this.maxAttibs = gl.getParameter(gl.MAX_VERTEX_ATTRIBS);

    this.attribState = [];

    for (var i = 0; i < this.maxAttibs; i++)
    {
        this.attribState[i] = false;
    }

    // TODO - Why are these not plugins? We can't decouple primitives unless they are....
    this.defaultShader = new TextureShader(this);
    this.primitiveShader = new PrimitiveShader(this);
    this.complexPrimitiveShader = new ComplexPrimitiveShader(this);
};

/**
 * Takes the attributes given in parameters and uploads them.
 *
 * @param attribs {any[]} attribs
 */
ShaderManager.prototype.setAttribs = function (attribs)
{
    // reset temp state
    var i;

    for (i = 0; i < this.tempAttribState.length; i++)
    {
        this.tempAttribState[i] = false;
    }

    // set the new attribs
    for (var a in attribs)
    {
        this.tempAttribState[attribs[a]] = true;
    }

    var gl = this.renderer.gl;

    for (i = 0; i < this.attribState.length; i++)
    {
        if (this.attribState[i] !== this.tempAttribState[i])
        {
            this.attribState[i] = this.tempAttribState[i];

            if (this.attribState[i])
            {
                gl.enableVertexAttribArray(i);
            }
            else
            {
                gl.disableVertexAttribArray(i);
            }
        }
    }
};

/**
 * Sets the current shader.
 *
 * @param shader {PIXI.Shader} the shader to upload
 */
ShaderManager.prototype.setShader = function (shader)
{
    if (this._currentId === shader.uid)
    {
        return false;
    }

    this._currentId = shader.uid;

    this.currentShader = shader;

    this.renderer.gl.useProgram(shader.program);
    this.setAttribs(shader.attributes);

    return true;
};

/**
 * Destroys this object.
 *
 */
ShaderManager.prototype.destroy = function ()
{
    this.primitiveShader.destroy();
    this.complexPrimitiveShader.destroy();
    WebGLManager.prototype.destroy.call(this);

    this.destroyPlugins();

    this.attribState = null;

    this.tempAttribState = null;
};