remoting/webapp/crd/js/bump_scroller.js

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 /**
   6  * @fileoverview
   7  * This class allows enables the scrolling of the DestkopViewport in fullscreen
   8  * mode by moving the mouse to the edge of the screen.
   9  */
  10
  11 /** @suppress {duplicate} */
  12 var remoting = remoting || {};
  13
  14 (function() {
  15
  16 'use strict';
  17
  18 /**
  19  * @param {remoting.DesktopViewport} viewport
  20  *
  21  * @constructor
  22  * @implements {base.Disposable}
  23  * @extends {base.EventSourceImpl}
  24  */
  25 remoting.BumpScroller = function(viewport) {
  26   base.inherits(this, base.EventSourceImpl);
  27
  28   /** @private */
  29   this.viewport_ = viewport;
  30   /** @private {number?} */
  31   this.bumpScrollTimer_ = null;
  32   /** @private */
  33   this.eventHook_ = new base.DomEventHook(document.documentElement, 'mousemove',
  34                                           this.onMouseMove_.bind(this), false);
  35
  36   this.defineEvents(base.values(remoting.BumpScroller.Events));
  37 };
  38
  39 /** @enum {string} */
  40 remoting.BumpScroller.Events = {
  41   bumpScrollStarted: 'bumpScrollStarted',
  42   bumpScrollStopped: 'bumpScrollStopped'
  43 };
  44
  45 remoting.BumpScroller.prototype.dispose = function() {
  46   base.dispose(this.eventHook_);
  47   this.eventHook_ = null;
  48 };
  49
  50 /**
  51  * @param {Event} event The mouse event.
  52  * @private
  53  */
  54 remoting.BumpScroller.prototype.onMouseMove_ = function(event) {
  55   if (this.bumpScrollTimer_ !== null) {
  56     window.clearTimeout(this.bumpScrollTimer_);
  57     this.bumpScrollTimer_ = null;
  58   }
  59
  60   /**
  61    * Compute the scroll speed based on how close the mouse is to the edge.
  62    *
  63    * @param {number} mousePos The mouse x- or y-coordinate
  64    * @param {number} size The width or height of the content area.
  65    * @return {number} The scroll delta, in pixels.
  66    */
  67   var computeDelta = function(mousePos, size) {
  68     var threshold = 10;
  69     if (mousePos >= size - threshold) {
  70       return 1 + 5 * (mousePos - (size - threshold)) / threshold;
  71     } else if (mousePos <= threshold) {
  72       return -1 - 5 * (threshold - mousePos) / threshold;
  73     }
  74     return 0;
  75   };
  76
  77   var clientArea = this.viewport_.getClientArea();
  78   var dx = computeDelta(event.x, clientArea.width);
  79   var dy = computeDelta(event.y, clientArea.height);
  80
  81   if (dx !== 0 || dy !== 0) {
  82     this.raiseEvent(remoting.BumpScroller.Events.bumpScrollStarted);
  83     this.repeatScroll_(dx, dy, new Date().getTime());
  84   }
  85 };
  86
  87 /**
  88  * Scroll the view, and schedule a timer to do so again unless we've hit
  89  * the edges of the screen. This timer is cancelled when the mouse moves.
  90  *
  91  * @param {number} dx
  92  * @param {number} dy
  93  * @param {number} expected The time at which we expect to be called.
  94  * @private
  95  */
  96 remoting.BumpScroller.prototype.repeatScroll_ = function(dx, dy, expected) {
  97   /** @type {number} */
  98   var now = new Date().getTime();
  99   var timeout = 10;
 100   var lateAdjustment = 1 + (now - expected) / timeout;
 101   if (!this.viewport_.scroll(lateAdjustment * dx, lateAdjustment * dy)) {
 102     this.raiseEvent(remoting.BumpScroller.Events.bumpScrollStopped);
 103   } else {
 104     this.bumpScrollTimer_ = window.setTimeout(
 105         this.repeatScroll_.bind(this, dx, dy, now + timeout), timeout);
 106   }
 107 };
 108
 109 }());