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What this is

This file is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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The source code

package org.apache.log4j.gui;


/**
 * Title:
 * Description:
 * Copyright:    Copyright (c) 2001
 * Company:
 * @author
 * @version 1.0
 */

import java.awt.Color;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.BorderLayout;

import javax.swing.*;
import javax.swing.text.StyledDocument;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.MutableAttributeSet;
import javax.swing.text.StyleConstants;

import java.util.Hashtable;
import java.util.StringTokenizer;
import java.util.Enumeration;
import java.util.ArrayList;

import org.apache.log4j.*;

public class LogTextPanel extends JPanel {

  private JScrollBar scrollBar;
  private JTextPane textPane;
  private JCheckBox cbxTail;
  private StyledDocument doc;

  private Hashtable fontAttributes;

  private int eventBufferMaxSize = 10000;
  private ArrayList eventBuffer = new ArrayList(eventBufferMaxSize);
  private int eventViewIndex = 0;

  public LogTextPanel() {
    constructComponents();
    createDefaultFontAttributes();
  }

  private void constructComponents() {
      // setup the panel's additional components...
    this.setLayout(new BorderLayout());

    cbxTail = new JCheckBox();
    cbxTail.setSelected(true);
    cbxTail.setText("Tail log events");

    JPanel bottomPanel = new JPanel();
    bottomPanel.add(cbxTail, null);

    textPane = new JTextPane();
    textPane.setEditable(false);
    textPane.setText("");
    doc = textPane.getStyledDocument();

    scrollBar = new JScrollBar(JScrollBar.VERTICAL);

    this.add(bottomPanel, BorderLayout.SOUTH);
    this.add(scrollBar, BorderLayout.EAST);
    this.add(textPane, BorderLayout.CENTER);
  }

  public
  void setTextBackground(Color color) {
    textPane.setBackground(color);
  }

  public
  void setTextBackground(String v) {
    textPane.setBackground(parseColor(v));
  }

  private void createDefaultFontAttributes() {
    Priority[] prio = Priority.getAllPossiblePriorities();

    fontAttributes = new Hashtable();
    for (int i=0; i= eventBufferMaxSize) {
      for(int i=0; i < evts.length; i++) {
        eventBuffer.remove(0);
      }
      eventViewIndex -= evts.length;
      if(eventViewIndex < 0)
        eventViewIndex = 0;
    }
    for(int i=0; i < evts.length; i++)
      eventBuffer.add(evts[i]);

    if((eventBuffer.size() > maxR) && cbxTail.isSelected()) {
      eventViewIndex = (eventBuffer.size() - maxR);
    }

    // only redraw if new line is visible...
    if((maxR < 0) || (eventBuffer.size() >= eventViewIndex && eventBuffer.size() <= (eventViewIndex + maxR)))
      drawText();
  }

  int maxR = -1;

  void drawText() {
    if(maxR < 0)
      maxR =  textPane.getHeight() / textPane.getFontMetrics(textPane.getFont()).getHeight();
    try {
      doc.remove(0, doc.getLength());
    } catch(Exception e) { e.printStackTrace(); }

    for(int i=eventViewIndex; (i < eventBuffer.size()) && (i < (eventViewIndex + maxR)); i++) {
      EventBufferElement evt = (EventBufferElement)eventBuffer.get(i);

      try {
        doc.insertString(doc.getLength(), evt.text, (MutableAttributeSet)fontAttributes.get(evt.prio));
      } catch(Exception e) { e.printStackTrace(); }
    }
  }


}
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