util.js

/*
 * Collection of useful "global" utility functions.
 *
 */
 
/* requireJS module definition */
define(["jquery","webgl-debug"], (function($, WebGLDebugUtils) {

    "use strict"; 
    
    // start with an empty object
    var util = {};

    /*
     *  This function asks the HTML Canvas element to create
     *  a context object for WebGL rendering.
     *
     *  It also creates awrapper around it for debugging 
     *  purposes, using webgl-debug.js
     *
     */
    
    util.makeWebGLContext = function(canvas_name) {
    
        // get the canvas element to be used for drawing
        var canvas=$("#"+canvas_name).get(0);
        if(!canvas) { 
            throw "HTML element with id '"+canvas_name + "' not found"; 
            return null;
        };

        // get WebGL rendering context for canvas element
        var options = {alpha: true, depth: true, antialias:true};
        var gl = canvas.getContext("webgl", options) || 
                 canvas.getContext("experimental-webgl", options);
        if(!gl) {
            throw "could not create WebGL rendering context";
        };
        
        // create a debugging wrapper of the context object
        var throwOnGLError = function(err, funcName, args) {
            throw WebGLDebugUtils.glEnumToString(err) + " was caused by call to: " + funcName;
        };
        var gl=WebGLDebugUtils.makeDebugContext(gl, throwOnGLError);
        
        return gl;
    };
            
    /** return the [x,y] position within the HTML canvas element.
        **Please note** that this will only work if the positioning 
        of the canvas element has been set to "relative"!
      */
    util.canvasPosition = function(event) {
      return [event.layerX,event.layerY];
    };
        
    /* return the interface defined by this module */
    return util;

})); // require 


 /*
 * The code below this comment is:
 * 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.
 */

/**
 * Provides requestAnimationFrame in a cross browser way.
 * (C)opyright 2010, Google Inc. 
 */
window.requestAnimFrame = (function() {
  return window.requestAnimationFrame ||
         window.webkitRequestAnimationFrame ||
         window.mozRequestAnimationFrame ||
         window.oRequestAnimationFrame ||
         window.msRequestAnimationFrame ||
         function(/* function FrameRequestCallback */ callback, /* DOMElement Element */ element) {
           return window.setTimeout(callback, 1000/60);
         };
})();

/**
 * Provides cancelRequestAnimationFrame in a cross browser way.
 * (C)opyright 2010, Google Inc. 
 */
window.cancelRequestAnimFrame = (function() {
  return window.cancelCancelRequestAnimationFrame ||
         window.webkitCancelRequestAnimationFrame ||
         window.mozCancelRequestAnimationFrame ||
         window.oCancelRequestAnimationFrame ||
         window.msCancelRequestAnimationFrame ||
         window.clearTimeout;
})();