wiggle.js

////////////////////////////////////////////////////////////////////////////////////////////////////
// File:      wiggle.js
// Purpose:   webgl helper functions. 
// Author:    Ryan McDonald <devops001@gmail.com> 
///////////////////////////////////////////////////////////////////////////////////////////////////

function initGL(canvas) {

  function setupFocusTracking() {
    function isHidden() {
      return document.hidden || document.webkitHidden || document.msHidden;
    }
    function focusChanged() {
      window.isHidden = isHidden();
    }
    document.addEventListener("visibilitychange",       focusChanged);
    document.addEventListener("webkitvisibilitychange", focusChanged);
    document.addEventListener("msvisibilitychange",     focusChanged);
  }

  function setupGL() {
    var gl = canvas.getContext("webgl");
    gl.clearColor(0.2, 0.3, 0.4, 1.0);
    gl.enable(gl.DEPTH_TEST);
    gl.depthFunc(gl.LEQUAL);
    gl.viewport(0, 0, canvas.width, canvas.height);
    return gl;
  }

  setupFocusTracking();
  return setupGL();
}

function initShader(gl, canvas) {

  function createShader(shaderType, shaderSource) {
    var shader = gl.createShader(shaderType);
    gl.shaderSource(shader, shaderSource);
    gl.compileShader(shader);
    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
      var error = gl.getShaderInfoLog(shader);
      var name  = shaderType==gl.VERTEX_SHADER ? "vertex shader" : "fragment shader";
      console.log(name +" failed to compile. error: "+ error +"\nsource:\n"+ shaderSource);
      return null;
    }
    return shader;
  }

  var vertexSource   = document.getElementById("vertex_shader").text;
  var fragmentSource = document.getElementById("fragment_shader").text;
  var vertexShader   = createShader(gl.VERTEX_SHADER, vertexSource);
  var fragmentShader = createShader(gl.FRAGMENT_SHADER, fragmentSource);
  var shaderProgram  = gl.createProgram();

  gl.attachShader(shaderProgram, vertexShader);
  gl.attachShader(shaderProgram, fragmentShader);
  gl.linkProgram(shaderProgram);

  if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
    var error = gl.getProgramInfoLog(shaderProgram);
    console.log("shader program failed to link: "+ error);
    gl.deleteProgram(shaderProgram);
    return null;
  }

  gl.useProgram(shaderProgram);
  return shaderProgram;
}

function render() {
  console.log("override the render() function to render things.");
}

function startRendering() {
  function renderLoop() {
    if (!window.isHidden) {
      window.currentFrame = window.requestAnimationFrame(renderLoop);
      render();
    }
  }
  renderLoop();
}

function stopRendering() {
  window.cancelAnimationFrame(window.currentFrame);
}