src/main/java/org/apache/log4j/chainsaw/WelcomePanel.java

/*
 * 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.chainsaw;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.io.IOException;
import java.net.URL;
import java.util.Stack;

import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JEditorPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JToolBar;
import javax.swing.SwingUtilities;
import javax.swing.event.HyperlinkEvent;

import org.apache.log4j.chainsaw.icons.ChainsawIcons;


/**
 * An initial Welcome Panel that is used when Chainsaw starts up, can displays
 * a HTML pages based on URLs.
 *
 * @author Paul Smith
 * @author Scott Deboy <sdeboy@apache.org>
 */
public class WelcomePanel extends JPanel {
  private Stack<URL> urlStack = new Stack<>();
  private final JEditorPane textInfo = new JEditorPane();
  private final URLToolbar urlToolbar = new URLToolbar();

  public WelcomePanel() {
    super(new BorderLayout());
    setBackground(Color.white);
    add(urlToolbar, BorderLayout.NORTH);

	URL helpURL = ChainsawConstants.WELCOME_URL;

    if (helpURL != null) {
      textInfo.setBorder(BorderFactory.createEmptyBorder(0, 5, 0, 5));

      JScrollPane pane = new JScrollPane(textInfo);
      pane.setBorder(null);
      add(pane, BorderLayout.CENTER);

      try {
        textInfo.setEditable(false);
        textInfo.setPreferredSize(new Dimension(320, 240));
        textInfo.setPage(helpURL);
        JTextComponentFormatter.applySystemFontAndSize(textInfo);
        textInfo.addHyperlinkListener(
                e -> {
                  if (e.getEventType() == HyperlinkEvent.EventType.ACTIVATED) {
                    urlStack.add(textInfo.getPage());

                    try {
                      textInfo.setPage(e.getURL());
                      urlToolbar.updateToolbar();
                    } catch (IOException e1) {
                      e1.printStackTrace();
                    }
                  }
                });
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }

  void setURL(final URL url) {
    SwingUtilities.invokeLater(
            () -> {
              try {
                urlStack.push(textInfo.getPage());
                textInfo.setPage(url);
                //not all pages displayed in the Welcome Panel are html-based (example receiver config is an xml file)..
                JTextComponentFormatter.applySystemFontAndSize(textInfo);
                urlToolbar.updateToolbar();
              } catch (IOException e) {
                e.printStackTrace();
              }
            });
  }

  private class URLToolbar extends JToolBar {
    private final Action previousAction =
      new AbstractAction(null, new ImageIcon(ChainsawIcons.ICON_BACK)) {
        public void actionPerformed(ActionEvent e) {
          if (urlStack.isEmpty()) {
            return;
          }

          setURL(urlStack.pop());
        }
      };

    private final Action homeAction =
      new AbstractAction(null, new ImageIcon(ChainsawIcons.ICON_HOME)) {
        public void actionPerformed(ActionEvent e) {
          setURL(ChainsawConstants.WELCOME_URL);
          urlStack.clear();
        }
      };

    private URLToolbar() {
      setFloatable(false);
      updateToolbar();
      previousAction.putValue(Action.SHORT_DESCRIPTION, "Back");
      homeAction.putValue(Action.SHORT_DESCRIPTION, "Home");

      JButton home = new SmallButton(homeAction);
      add(home);

      addSeparator();

      JButton previous = new SmallButton(previousAction);
      previous.setEnabled(false);
      add(previous);

      addSeparator();
    }

    void updateToolbar() {
      previousAction.setEnabled(!urlStack.isEmpty());
    }
  }

  /**
   * @return tooolbar
   */
  public JToolBar getToolbar() {
    return urlToolbar;
  }
}