[polymer] Merge of master into polymer10-migration

netlog_viewer/horizontal_scrollbar_view.js

+// Copyright (c) 2011 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.
+
+/**
+ * This view consists of two nested divs.  The outer one has a horizontal
+ * scrollbar and the inner one has a height of 1 pixel and a width set to
+ * allow an appropriate scroll range.  The view reports scroll events to
+ * a callback specified on construction.
+ *
+ * All this funkiness is necessary because there is no HTML scroll control.
+ * TODO(mmenke):  Consider implementing our own scrollbar directly.
+ */
+var HorizontalScrollbarView = (function() {
+  'use strict';
+
+  // We inherit from DivView.
+  var superClass = DivView;
+
+  /**
+   * @constructor
+   */
+  function HorizontalScrollbarView(divId, innerDivId, callback) {
+    superClass.call(this, divId);
+    this.callback_ = callback;
+    this.innerDiv_ = $(innerDivId);
+    $(divId).onscroll = this.onScroll_.bind(this);
+
+    // The current range and position of the scrollbar.  Because DOM updates
+    // are asynchronous, the current state cannot be read directly from the DOM
+    // after updating the range.
+    this.range_ = 0;
+    this.position_ = 0;
+
+    // The DOM updates asynchronously, so sometimes we need a timer to update
+    // the current scroll position after resizing the scrollbar.
+    this.updatePositionTimerId_ = null;
+  }
+
+  HorizontalScrollbarView.prototype = {
+    // Inherit the superclass's methods.
+    __proto__: superClass.prototype,
+
+    setGeometry: function(left, top, width, height) {
+      superClass.prototype.setGeometry.call(this, left, top, width, height);
+      this.setRange(this.range_);
+    },
+
+    show: function(isVisible) {
+      superClass.prototype.show.call(this, isVisible);
+    },
+
+    /**
+     * Sets the range of the scrollbar.  The scrollbar can have a value
+     * anywhere from 0 to |range|, inclusive.  The width of the drag area
+     * on the scrollbar will generally be based on the width of the scrollbar
+     * relative to the size of |range|, so if the scrollbar is about the size
+     * of the thing we're scrolling, we get fairly nice behavior.
+     *
+     * If |range| is less than the original position, |position_| is set to
+     * |range|.  Otherwise, it is not modified.
+     */
+    setRange: function(range) {
+      this.range_ = range;
+      setNodeWidth(this.innerDiv_, this.getWidth() + range);
+      if (range < this.position_)
+        this.position_ = range;
+      this.setPosition(this.position_);
+    },
+
+    /**
+     * Sets the position of the scrollbar.  |position| must be between 0 and
+     * |range_|, inclusive.
+     */
+    setPosition: function(position) {
+      this.position_ = position;
+      this.updatePosition_();
+    },
+
+    /**
+     * Updates the visible position of the scrollbar to be |position_|.
+     * On failure, calls itself again after a timeout.  This is needed because
+     * setRange does not synchronously update the DOM.
+     */
+    updatePosition_: function() {
+      // Clear the timer if we have one, so we don't have two timers running at
+      // once.  This is safe even if we were just called from the timer, in
+      // which case clearTimeout will silently fail.
+      if (this.updatePositionTimerId_ !== null) {
+        window.clearTimeout(this.updatePositionTimerId_);
+        this.updatePositionTimerId_ = null;
+      }
+
+      this.getNode().scrollLeft = this.position_;
+      if (this.getNode().scrollLeft != this.position_) {
+        this.updatePositionTimerId_ =
+            window.setTimeout(this.updatePosition_.bind(this));
+      }
+    },
+
+    getRange: function() {
+      return this.range_;
+    },
+
+    getPosition: function() {
+      return this.position_;
+    },
+
+    onScroll_: function() {
+      // If we're waiting to update the range, ignore messages from the
+      // scrollbar.
+      if (this.updatePositionTimerId_ !== null)
+        return;
+      var newPosition = this.getNode().scrollLeft;
+      if (newPosition == this.position_)
+        return;
+      this.position_ = newPosition;
+      this.callback_();
+    }
+  };
+
+  return HorizontalScrollbarView;
+})();
+