sdk/pkg/template_binding/lib/js/flush.js

/*
 * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */

(function(scope) {

/**
 * @class Polymer
 */

// imports
var endOfMicrotask = scope.endOfMicrotask;

// logging
var log = window.WebComponents ? WebComponents.flags.log : {};

// inject style sheet
var style = document.createElement('style');
style.textContent = 'template {display: none !important;} /* injected by platform.js */';
var head = document.querySelector('head');
head.insertBefore(style, head.firstChild);


/**
 * Force any pending data changes to be observed before 
 * the next task. Data changes are processed asynchronously but are guaranteed
 * to be processed, for example, before paintin. This method should rarely be 
 * needed. It does nothing when Object.observe is available; 
 * when Object.observe is not available, Polymer automatically flushes data 
 * changes approximately every 1/10 second. 
 * Therefore, `flush` should only be used when a data mutation should be 
 * observed sooner than this.
 * 
 * @method flush
 */
// flush (with logging)
var flushing;
function flush() {
  if (!flushing) {
    flushing = true;
    endOfMicrotask(function() {
      flushing = false;
      log.data && console.group('flush');
      Platform.performMicrotaskCheckpoint();
      log.data && console.groupEnd();
    });
  }
};

// polling dirty checker
// flush periodically if platform does not have object observe.
if (!Observer.hasObjectObserve) {
  var FLUSH_POLL_INTERVAL = 125;
  window.addEventListener('WebComponentsReady', function() {
    flush();
    // watch document visiblity to toggle dirty-checking
    var visibilityHandler = function() {
      // only flush if the page is visibile
      if (document.visibilityState === 'hidden') {
        if (scope.flushPoll) {
          clearInterval(scope.flushPoll);
        }
      } else {
        scope.flushPoll = setInterval(flush, FLUSH_POLL_INTERVAL);
      }
    };
    if (typeof document.visibilityState === 'string') {
      document.addEventListener('visibilitychange', visibilityHandler);
    }
    visibilityHandler();
  });
} else {
  // make flush a no-op when we have Object.observe
  flush = function() {};
}

if (window.CustomElements && !CustomElements.useNative) {
  var originalImportNode = Document.prototype.importNode;
  Document.prototype.importNode = function(node, deep) {
    var imported = originalImportNode.call(this, node, deep);
    CustomElements.upgradeAll(imported);
    return imported;
  };
}

// exports
scope.flush = flush;
// bc
Platform.flush = flush;

})(window.Polymer);