/*
* 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" target="_blank">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/" target="_blank">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);
         };
})();