CRD Viewport Management refactor

remoting/webapp/crd/js/bump_scroller.js

+// Copyright 2015 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
+ * This class allows enables the scrolling of the DestkopViewport in fullscreen
+ * mode by moving the mouse to the edge of the screen.
+ */
+
+/** @suppress {duplicate} */
+var remoting = remoting || {};
+
+(function() {
+
+'use strict';
+
+/**
+ * @param {remoting.DesktopViewport} viewport
+ *
+ * @constructor
+ * @implements {base.Disposable}
+ * @extends {base.EventSourceImpl}
+ */
+remoting.BumpScroller = function(viewport) {
+  /** @private */
+  this.viewport_ = viewport;
+  /** @private {number?} */
+  this.bumpScrollTimer_ = null;
+  /** @private */
+  this.eventHook_ = new base.DomEventHook(document.documentElement, 'mousemove',
+                                          this.onMouseMove_.bind(this), false);
+
+  this.defineEvents(base.values(remoting.BumpScroller.Events));
+};
+base.extend(remoting.BumpScroller, base.EventSourceImpl);
+
+/** @enum {string} */
+remoting.BumpScroller.Events = {
+  bumpScrollStarted: 'bumpScrollStarted',
+  bumpScrollStopped: 'bumpScrollStopped'
+};
+
+remoting.BumpScroller.prototype.dispose = function() {
+  base.dispose(this.eventHook_);
+  this.eventHook_ = null;
+};
+
+/**
+ * @param {Event} event The mouse event.
+ * @private
+ */
+remoting.BumpScroller.prototype.onMouseMove_ = function(event) {
+  if (this.bumpScrollTimer_ !== null) {
+    window.clearTimeout(this.bumpScrollTimer_);
+    this.bumpScrollTimer_ = null;
+  }
+
+  /**
+   * Compute the scroll speed based on how close the mouse is to the edge.
+   *
+   * @param {number} mousePos The mouse x- or y-coordinate
+   * @param {number} size The width or height of the content area.
+   * @return {number} The scroll delta, in pixels.
+   */
+  var computeDelta = function(mousePos, size) {
+    var threshold = 10;
+    if (mousePos >= size - threshold) {
+      return 1 + 5 * (mousePos - (size - threshold)) / threshold;
+    } else if (mousePos <= threshold) {
+      return -1 - 5 * (threshold - mousePos) / threshold;
+    }
+    return 0;
+  };
+
+  var clientArea = this.viewport_.getClientArea();
+  var dx = computeDelta(event.x, clientArea.width);
+  var dy = computeDelta(event.y, clientArea.height);
+
+  if (dx !== 0 || dy !== 0) {
+    this.raiseEvent(remoting.BumpScroller.Events.bumpScrollStarted);
+    this.repeatScroll_(dx, dy, new Date().getTime());
+  }
+};
+
+/**
+ * Scroll the view, and schedule a timer to do so again unless we've hit
+ * the edges of the screen. This timer is cancelled when the mouse moves.
+ *
+ * @param {number} dx
+ * @param {number} dy
+ * @param {number} expected The time at which we expect to be called.
+ * @private
+ */
+remoting.BumpScroller.prototype.repeatScroll_ = function(dx, dy, expected) {
+  /** @type {number} */
+  var now = new Date().getTime();
+  var timeout = 10;
+  var lateAdjustment = 1 + (now - expected) / timeout;
+  if (!this.viewport_.scroll(lateAdjustment * dx, lateAdjustment * dy)) {
+    this.raiseEvent(remoting.BumpScroller.Events.bumpScrollStopped);
+  } else {
+    this.bumpScrollTimer_ = window.setTimeout(
+        this.repeatScroll_.bind(this, dx, dy, now + timeout), timeout);
+  }
+};
+
+}());