/*

 * 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);

         };

})();