MD Settings: animation interface

chrome/browser/resources/settings/animation/animation.js

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @fileoverview Simplified API wrapping native Web Animations with some sugar.
+ * A compromise between the draft spec and Chrome's evolving support. This API
+ * will be changed (or removed) as Chrome support evolves.
+ */
+cr.define('settings.animation', function() {
+  'use strict';
+
+  /**
+   * Default timing constants.
+   * @const
+   */
+  var Timing = {
+    DURATION: 250,
+    EASING: 'cubic-bezier(0.4, 0, 0.2, 1)',  // Fast out, slow in.
+  };
+
+  /**
+   * Offers a small subset of the v1 Animation interface. The underlying
+   * animation can be reversed, canceled or immediately finished.
+   * @see https://www.w3.org/TR/web-animations-1/#animation
+   *
+   * @constructor
+   * @extends {cr.EventTarget}
+   * @param {!Element} el The element to animate.
+   * @param {!Array<!Object>|!Object<!Array>|!Object<string>} keyframes
+   *     Keyframes, as in Element.prototype.animate.
+   * @param {number|!KeyframeEffectOptions=} opt_options Duration or options
+   *     object, as in Element.prototype.animate.
+   */
+  function Animation(el, keyframes, opt_options) {
+    // Disallow direct usage of the underlying animation.
+    this.animation_ = el.animate(keyframes, opt_options);
+
+    var self = this;
+    /** @type {!Promise} */
+    this.finished = new Promise(function(resolve, reject) {

[Dan Beam, 2016/07/01 00:33:58]

so the point of this class is just basically to add this |finished| promise,
right?

[michaelpg, 2016/07/01 20:21:46]

Yes, that's entirely the point. Once the platform adds |finished| we replace all
    new settings.animation.Animation(el, ...)
with
    el.animate(...)

web-animations-next-lite does something similar but ideally we remove that
(crbug.com/584126)

+      // If we were implementing the full spec, we'd have to support
+      // removing or resetting these listeners.
+      self.animation_.addEventListener('finish', function(e) {
+        resolve();
+        // According to the spec, queue a task to fire the event after
+        // resolving the promise.
+        self.queueDispatch_(e);
+      });
+      self.animation_.addEventListener('cancel', function(e) {
+        reject(new
+            /**
+             * @see https://heycam.github.io/webidl/#es-DOMException-call
+             * @type {function (new:DOMException, string, string)}
+             */(
+                DOMException
+            )('', 'AbortError'));
+        self.queueDispatch_(e);
+      });
+    });
+  }
+
+  Animation.prototype = {
+    __proto__: cr.EventTarget.prototype,
+
+    finish: function() {
+      assert(this.animation_);
+      this.animation_.finish();
+    },
+
+    cancel: function() {
+      assert(this.animation_);
+      this.animation_.cancel();
+    },
+
+    /**
+     * @param {!Event} e
+     * @private
+     */
+    queueDispatch_: function(e) {
+      setTimeout(function() {
+        this.dispatchEvent(e);
+        this.animation_ = undefined;
+      }.bind(this));
+    },
+  };
+
+  return {
+    Animation: Animation,
+    Timing: Timing,
+  };
+});