From b26a7695b88b44186aca11fc305c34552d958ad1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Benjamin=20Strau=C3=9F?= <b.strauss@netzbewegung.com>
Date: Wed, 24 Jan 2018 19:01:58 +0100
Subject: [PATCH] feat(animation): RenderLoop

---
 src/animation/rendering.js  | 98 +++++++++++++++++++++++++++++++++++++
 test/animation/rendering.js | 52 ++++++++++++++++++++
 test/test_main.js           |  2 +
 3 files changed, 152 insertions(+)
 create mode 100644 src/animation/rendering.js
 create mode 100644 test/animation/rendering.js

diff --git a/src/animation/rendering.js b/src/animation/rendering.js
new file mode 100644
index 0000000..13631e2
--- /dev/null
+++ b/src/animation/rendering.js
@@ -0,0 +1,98 @@
+goog.module('clulib.animation.rendering');
+
+const EventTarget = goog.require('goog.events.EventTarget');
+const Event = goog.require('goog.events.Event');
+
+/**
+ * A render loop which runs on requestAnimationFrame.
+ *
+ * Dispatches RenderLoopEvents
+ */
+class RenderLoop extends EventTarget {
+  constructor () {
+    super();
+
+    /**
+     * @type {boolean}
+     * @private
+     */
+    this.isRunning_ = false;
+
+    /**
+     * @type {?number}
+     * @private
+     */
+    this.id_ = null;
+  }
+
+  /**
+   * @returns {boolean}
+   */
+  get isRunning () {
+    return this.isRunning_;
+  }
+
+  start () {
+    if (this.isRunning_)
+      return;
+    this.id_ = window.requestAnimationFrame(this.tick_.bind(this));
+    this.isRunning_ = true;
+    this.dispatchEvent(new RenderLoopEvent(RenderLoopEventType.START, this));
+  }
+
+  /**
+   * @param {number} highResolutionTimestamp
+   * @private
+   */
+  tick_ (highResolutionTimestamp) {
+    this.dispatchEvent(new RenderLoopEvent(RenderLoopEventType.TICK, this, highResolutionTimestamp));
+  }
+
+  stop () {
+    if (!this.isRunning_)
+      return;
+    window.cancelAnimationFrame(/** @type {number} */ (this.id_));
+    this.isRunning_ = false;
+    this.dispatchEvent(new RenderLoopEvent(RenderLoopEventType.END, this));
+  }
+}
+
+/**
+ * The event for RenderLoop. Holds the elapsed time.
+ */
+class RenderLoopEvent extends Event {
+  /**
+   * @param {RenderLoopEventType} type
+   * @param {RenderLoop} target
+   * @param {number=} elapsedTime
+   */
+  constructor (type, target, elapsedTime) {
+    super(type, target);
+
+    /**
+     * @type {?number}
+     * @private
+     */
+    this.elapsedTime_ = /** @type {?number} */ (elapsedTime);
+  }
+
+  /**
+   * The elapsed time since the last tick in milliseconds.
+   *
+   * @returns {?number}
+   */
+  get elapsedTime () {
+    return this.elapsedTime_;
+  }
+}
+
+/**
+ * @enum {string}
+ */
+const RenderLoopEventType = {
+  START: 'start',
+  TICK: 'tick',
+  END: 'end'
+};
+
+exports = {RenderLoop, RenderLoopEvent, RenderLoopEventType};
diff --git a/test/animation/rendering.js b/test/animation/rendering.js
new file mode 100644
index 0000000..c640434
--- /dev/null
+++ b/test/animation/rendering.js
@@ -0,0 +1,52 @@
+goog.module('test.clulib.animation.rendering');
+
+const {RenderLoop, RenderLoopEventType} = goog.require('clulib.animation.rendering');
+
+/**
+ * @param {number} ms
+ * @returns {Promise<void>}
+ */
+const waitFor = function (ms) {
+  return new Promise(resolve => {
+    setTimeout(() => {
+      resolve();
+    }, ms);
+  });
+};
+
+exports = function () {
+  describe('clulib.animation.rendering', () => {
+    describe('RenderLoop', () => {
+      it('should dispatch tick events', async () => {
+        const loop = new RenderLoop();
+        let started = false;
+        let ticked = false;
+        let ended = false;
+        let elapsedTime = 0;
+
+        loop.addEventListener(RenderLoopEventType.START, () => {
+          started = true;
+        });
+
+        loop.addEventListener(RenderLoopEventType.TICK, event => {
+          ticked = true;
+          elapsedTime = event.elapsedTime;
+          loop.stop();
+        });
+
+        loop.addEventListener(RenderLoopEventType.END, () => {
+          ended = true;
+        });
+
+        loop.start();
+
+        await waitFor(1000);
+
+        expect(started).toBe(true);
+        expect(ticked).toBe(true);
+        expect(ended).toBe(true);
+        expect(elapsedTime > 0).toBe(true);
+      });
+    });
+  });
+};
diff --git a/test/test_main.js b/test/test_main.js
index 31854b5..5444b7b 100644
--- a/test/test_main.js
+++ b/test/test_main.js
@@ -1,5 +1,6 @@
 goog.module('test.main');
 
+const renderingMain = goog.require('test.clulib.animation.rendering');
 const arrayMain = goog.require('test.clulib.array');
 const asyncCompleterMain = goog.require('test.clulib.async.Completer');
 const cmMain = goog.require('test.clulib.cm');
@@ -11,6 +12,7 @@ const resourceManagerMain = goog.require('test.clulib.l10n.ResourceManager');
 const httpRequestMain = goog.require('test.clulib.net.http_request');
 const mathMain = goog.require('test.clulib.math');
 
+renderingMain();
 arrayMain();
 asyncCompleterMain();
 cmMain();