michael@0: WebGLUtil = (function() {
michael@0:   // ---------------------------------------------------------------------------
michael@0:   // Error handling (for obvious failures, such as invalid element ids)
michael@0: 
michael@0:   function defaultErrorFunc(str) {
michael@0:     console.log('Error: ' + str);
michael@0:   }
michael@0: 
michael@0:   var gErrorFunc = defaultErrorFunc;
michael@0:   function setErrorFunc(func) {
michael@0:     gErrorFunc = func;
michael@0:   }
michael@0: 
michael@0:   function error(str) {
michael@0:     gErrorFunc(str);
michael@0:   }
michael@0: 
michael@0:   // ---------------------------------------------------------------------------
michael@0:   // Warning handling (for failures that may be intentional)
michael@0: 
michael@0:   function defaultWarningFunc(str) {
michael@0:     console.log('Warning: ' + str);
michael@0:   }
michael@0: 
michael@0:   var gWarningFunc = defaultWarningFunc;
michael@0:   function setWarningFunc(func) {
michael@0:     gWarningFunc = func;
michael@0:   }
michael@0: 
michael@0:   function warning(str) {
michael@0:     gWarningFunc(str);
michael@0:   }
michael@0: 
michael@0:   // ---------------------------------------------------------------------------
michael@0:   // WebGL helpers
michael@0: 
michael@0:   function getWebGL(canvasId, requireConformant) {
michael@0:     // `requireConformant` will default to falsey if it is not supplied.
michael@0: 
michael@0:     var canvas = document.getElementById(canvasId);
michael@0: 
michael@0:     var gl = null;
michael@0:     try {
michael@0:       gl = canvas.getContext('webgl');
michael@0:     } catch(e) {}
michael@0: 
michael@0:     if (!gl && !requireConformant) {
michael@0:       try {
michael@0:         gl = canvas.getContext('experimental-webgl');
michael@0:       } catch(e) {}
michael@0:     }
michael@0: 
michael@0:     if (!gl) {
michael@0:       error('WebGL context could not be retrieved from \'' + canvasId + '\'.');
michael@0:       return null;
michael@0:     }
michael@0: 
michael@0:     return gl;
michael@0:   }
michael@0: 
michael@0:   function getContentFromElem(elem) {
michael@0:     var str = "";
michael@0:     var k = elem.firstChild;
michael@0:     while (k) {
michael@0:       if (k.nodeType == 3)
michael@0:         str += k.textContent;
michael@0: 
michael@0:       k = k.nextSibling;
michael@0:     }
michael@0: 
michael@0:     return str;
michael@0:   }
michael@0: 
michael@0:   // Returns a valid shader, or null on errors.
michael@0:   function createShaderById(gl, id) {
michael@0:     var elem = document.getElementById(id);
michael@0:     if (!elem) {
michael@0:       error('Failed to create shader from non-existent id \'' + id + '\'.');
michael@0:       return null;
michael@0:     }
michael@0: 
michael@0:     var src = getContentFromElem(elem);
michael@0: 
michael@0:     var shader;
michael@0:     if (elem.type == "x-shader/x-fragment") {
michael@0:       shader = gl.createShader(gl.FRAGMENT_SHADER);
michael@0:     } else if (elem.type == "x-shader/x-vertex") {
michael@0:       shader = gl.createShader(gl.VERTEX_SHADER);
michael@0:     } else {
michael@0:       error('Bad MIME type for shader \'' + id + '\': ' + elem.type + '.');
michael@0:       return null;
michael@0:     }
michael@0: 
michael@0:     gl.shaderSource(shader, src);
michael@0:     gl.compileShader(shader);
michael@0: 
michael@0:     return shader;
michael@0:   }
michael@0: 
michael@0:   function createProgramByIds(gl, vsId, fsId) {
michael@0:     var vs = createShaderById(gl, vsId);
michael@0:     var fs = createShaderById(gl, fsId);
michael@0:     if (!vs || !fs)
michael@0:       return null;
michael@0: 
michael@0:     var prog = gl.createProgram();
michael@0:     gl.attachShader(prog, vs);
michael@0:     gl.attachShader(prog, fs);
michael@0:     gl.linkProgram(prog);
michael@0: 
michael@0:     if (!gl.getProgramParameter(prog, gl.LINK_STATUS)) {
michael@0:       var str = "Shader program linking failed:";
michael@0:       str += "\nShader program info log:\n" + gl.getProgramInfoLog(prog);
michael@0:       str += "\n\nVert shader log:\n" + gl.getShaderInfoLog(vs);
michael@0:       str += "\n\nFrag shader log:\n" + gl.getShaderInfoLog(fs);
michael@0:       warning(str);
michael@0:       return null;
michael@0:     }
michael@0: 
michael@0:     return prog;
michael@0:   }
michael@0: 
michael@0:   return {
michael@0:     setErrorFunc: setErrorFunc,
michael@0:     setWarningFunc: setWarningFunc,
michael@0: 
michael@0:     getWebGL: getWebGL,
michael@0:     createShaderById: createShaderById,
michael@0:     createProgramByIds: createProgramByIds,
michael@0:   };
michael@0: })();