chrome/browser/resources/net_internals/horizontal_scrollbar_view.js

   1 // Copyright (c) 2011 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  * This view consists of two nested divs.  The outer one has a horizontal
   7  * scrollbar and the inner one has a height of 1 pixel and a width set to
   8  * allow an appropriate scroll range.  The view reports scroll events to
   9  * a callback specified on construction.
  10  *
  11  * All this funkiness is necessary because there is no HTML scroll control.
  12  * TODO(mmenke):  Consider implementing our own scrollbar directly.
  13  */
  14 var HorizontalScrollbarView = (function() {
  15   'use strict';
  16
  17   // We inherit from DivView.
  18   var superClass = DivView;
  19
  20   /**
  21    * @constructor
  22    */
  23   function HorizontalScrollbarView(divId, innerDivId, callback) {
  24     superClass.call(this, divId);
  25     this.callback_ = callback;
  26     this.innerDiv_ = $(innerDivId);
  27     $(divId).onscroll = this.onScroll_.bind(this);
  28
  29     // The current range and position of the scrollbar.  Because DOM updates
  30     // are asynchronous, the current state cannot be read directly from the DOM
  31     // after updating the range.
  32     this.range_ = 0;
  33     this.position_ = 0;
  34
  35     // The DOM updates asynchronously, so sometimes we need a timer to update
  36     // the current scroll position after resizing the scrollbar.
  37     this.updatePositionTimerId_ = null;
  38   }
  39
  40   HorizontalScrollbarView.prototype = {
  41     // Inherit the superclass's methods.
  42     __proto__: superClass.prototype,
  43
  44     setGeometry: function(left, top, width, height) {
  45       superClass.prototype.setGeometry.call(this, left, top, width, height);
  46       this.setRange(this.range_);
  47     },
  48
  49     show: function(isVisible) {
  50       superClass.prototype.show.call(this, isVisible);
  51     },
  52
  53     /**
  54      * Sets the range of the scrollbar.  The scrollbar can have a value
  55      * anywhere from 0 to |range|, inclusive.  The width of the drag area
  56      * on the scrollbar will generally be based on the width of the scrollbar
  57      * relative to the size of |range|, so if the scrollbar is about the size
  58      * of the thing we're scrolling, we get fairly nice behavior.
  59      *
  60      * If |range| is less than the original position, |position_| is set to
  61      * |range|.  Otherwise, it is not modified.
  62      */
  63     setRange: function(range) {
  64       this.range_ = range;
  65       setNodeWidth(this.innerDiv_, this.getWidth() + range);
  66       if (range < this.position_)
  67         this.position_ = range;
  68       this.setPosition(this.position_);
  69     },
  70
  71     /**
  72      * Sets the position of the scrollbar.  |position| must be between 0 and
  73      * |range_|, inclusive.
  74      */
  75     setPosition: function(position) {
  76       this.position_ = position;
  77       this.updatePosition_();
  78     },
  79
  80     /**
  81      * Updates the visible position of the scrollbar to be |position_|.
  82      * On failure, calls itself again after a timeout.  This is needed because
  83      * setRange does not synchronously update the DOM.
  84      */
  85     updatePosition_: function() {
  86       // Clear the timer if we have one, so we don't have two timers running at
  87       // once.  This is safe even if we were just called from the timer, in
  88       // which case clearTimeout will silently fail.
  89       if (this.updatePositionTimerId_ !== null) {
  90         window.clearTimeout(this.updatePositionTimerId_);
  91         this.updatePositionTimerId_ = null;
  92       }
  93
  94       this.getNode().scrollLeft = this.position_;
  95       if (this.getNode().scrollLeft != this.position_) {
  96         this.updatePositionTimerId_ =
  97             window.setTimeout(this.updatePosition_.bind(this));
  98       }
  99     },
 100
 101     getRange: function() {
 102       return this.range_;
 103     },
 104
 105     getPosition: function() {
 106       return this.position_;
 107     },
 108
 109     onScroll_: function() {
 110       // If we're waiting to update the range, ignore messages from the
 111       // scrollbar.
 112       if (this.updatePositionTimerId_ !== null)
 113         return;
 114       var newPosition = this.getNode().scrollLeft;
 115       if (newPosition == this.position_)
 116         return;
 117       this.position_ = newPosition;
 118       this.callback_();
 119     }
 120   };
 121
 122   return HorizontalScrollbarView;
 123 })();