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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.log4j.lf5.viewer;
import java.awt.Adjustable;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;
/**
* An AdjustmentListener which ensures that an Adjustable (e.g. a Scrollbar)
* will "track" when the Adjustable expands.
* For example, when a vertical scroll bar is at its bottom anchor,
* the scrollbar will remain at the bottom. When the vertical scroll bar
* is at any other location, then no tracking will happen.
* An instance of this class should only listen to one Adjustable as
* it retains state information about the Adjustable it listens to.
*
* @author Richard Wan
*/
// Contributed by ThoughtWorks Inc.
public class TrackingAdjustmentListener implements AdjustmentListener {
//--------------------------------------------------------------------------
// Constants:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Protected Variables:
//--------------------------------------------------------------------------
protected int _lastMaximum = -1;
//--------------------------------------------------------------------------
// Private Variables:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Constructors:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Public Methods:
//--------------------------------------------------------------------------
public void adjustmentValueChanged(AdjustmentEvent e) {
Adjustable bar = e.getAdjustable();
int currentMaximum = bar.getMaximum();
if (bar.getMaximum() == _lastMaximum) {
return; // nothing to do, the adjustable has not expanded
}
int bottom = bar.getValue() + bar.getVisibleAmount();
if (bottom + bar.getUnitIncrement() >= _lastMaximum) {
bar.setValue(bar.getMaximum()); // use the most recent maximum
}
_lastMaximum = currentMaximum;
}
//--------------------------------------------------------------------------
// Protected Methods:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Private Methods:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Nested Top-Level Classes or Interfaces
//--------------------------------------------------------------------------
}