/*

  * Copyright 2010, Google Inc.

  * All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions are

  * met:

  *

  *     * Redistributions of source code must retain the above copyright

  * notice, this list of conditions and the following disclaimer.

  *     * Redistributions in binary form must reproduce the above

  * copyright notice, this list of conditions and the following disclaimer

  * in the documentation and/or other materials provided with the

  * distribution.

  *     * Neither the name of Google Inc. nor the names of its

  * contributors may be used to endorse or promote products derived from

  * this software without specific prior written permission.

  *

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  */

 /**

  * @fileoverview This file contains functions every webgl program will need

  * a version of one way or another.

  *

  * Instead of setting up a context manually it is recommended to

  * use. This will check for success or failure. On failure it

  * will attempt to present an approriate message to the user.

  *

  *       gl = WebGLUtils.setupWebGL(canvas);

  *

  * For animated WebGL apps use of setTimeout or setInterval are

  * discouraged. It is recommended you structure your rendering

  * loop like this.

  *

  *       function render() {

  *         window.requestAnimFrame(render, canvas);

  *

  *         // do rendering

  *         ...

  *       }

  *       render();

  *

  * This will call your rendering function up to the refresh rate

  * of your display but will stop rendering if your app is not

  * visible.

  */

 WebGLUtils = function() {

 /**

  * Creates the HTLM for a failure message

  * @param {string} canvasContainerId id of container of th

  *        canvas.

  * @return {string} The html.

  */

 var makeFailHTML = function(msg) {

   return '' +

     '<table style="background-color: #8CE; width: 100%; height: 100%;"><tr>' +

     '<td align="center">' +

     '<div style="display: table-cell; vertical-align: middle;">' +

     '<div style="">' + msg + '</div>' +

     '</div>' +

     '</td></tr></table>';

 };

 /**

  * Mesasge for getting a webgl browser

  * @type {string}

  */

 var GET_A_WEBGL_BROWSER = '' +

   'This page requires a browser that supports WebGL.<br/>' +

   '<a href="http://get.webgl.org">Click here to upgrade your browser.</a>';

 /**

  * Mesasge for need better hardware

  * @type {string}

  */

 var OTHER_PROBLEM = '' +

   "It doesn't appear your computer can support WebGL.<br/>" +

   '<a href="http://get.webgl.org/troubleshooting/">Click here for more information.</a>';

 /**

  * Creates a webgl context. If creation fails it will

  * change the contents of the container of the <canvas>

  * tag to an error message with the correct links for WebGL.

  * @param {Element} canvas. The canvas element to create a

  *     context from.

  * @param {WebGLContextCreationAttirbutes} opt_attribs Any

  *     creation attributes you want to pass in.

  * @return {WebGLRenderingContext} The created context.

  */

 var setupWebGL = function(canvas, opt_attribs) {

   function showLink(str) {

     var container = canvas.parentNode;

     if (container) {

       container.innerHTML = makeFailHTML(str);

     }

   };

   if (!window.WebGLRenderingContext) {

     showLink(GET_A_WEBGL_BROWSER);

     return null;

   }

   var context = create3DContext(canvas, opt_attribs);

   if (!context) {

     showLink(OTHER_PROBLEM);

   }

   return context;

 };

 /**

  * Creates a webgl context.

  * @param {!Canvas} canvas The canvas tag to get context

  *     from. If one is not passed in one will be created.

  * @return {!WebGLContext} The created context.

  */

 var create3DContext = function(canvas, opt_attribs) {

   var names = ["webgl", "experimental-webgl", "webkit-3d", "moz-webgl"];

   var context = null;

   for (var ii = 0; ii < names.length; ++ii) {

     try {

       context = canvas.getContext(names[ii], opt_attribs);

     } catch(e) {}

     if (context) {

       break;

     }

   }

   return context;

 }

 return {

   create3DContext: create3DContext,

   setupWebGL: setupWebGL

 };

 }();

 /**

  * Provides requestAnimationFrame in a cross browser way.

  */

 window.requestAnimFrame = (function() {

   return window.requestAnimationFrame ||

          window.webkitRequestAnimationFrame ||

          window.mozRequestAnimationFrame ||

          window.oRequestAnimationFrame ||

          window.msRequestAnimationFrame ||

          function(/* function FrameRequestCallback */ callback, /* DOMElement Element */ element) {

            window.setTimeout(callback, 1000/60);

          };

 })();