Customize the Outline View in Text Mode

Suppose that you have the following XML document:

<doc startnumber="15">
    <sec counter="no">
        <info/>
        <title>Introduction</title>   
      </sec>
    <sec>
        <title>Section title</title>       
      <para>Content</para>
        <sec>
            <title>Section title</title> 
                <para>Content</para>
        </sec>
    </sec>
    <sec> 
            <title>Section title</title>
        <para>Content</para>   
      </sec>
</doc>

and you want to display the XML content in a simplified Outline view like this:

doc "15"
sec Introduction
sec 15 Section title
sec 15.1 Section title
sec 16 Section title

Usually, an Outline view should have the following characteristics:

1. Double-clicking a node in the Outline view would select the corresponding XML content in the editor.
2. When the cursor moves in the open XML document, the Outline view would select the proper entry.
3. When modifications occur in the document, the Outline view would refresh.

A simple implementation using a Workspace Access plugin type could be something like this:

/**
 * Simple Outline for Text mode based on executing XPaths over the text content.
 */
 public class CustomWorkspaceAccessPluginExtension implements 
WorkspaceAccessPluginExtension {
  /**
   * The custom outline list.
   */
  private JList customOutlineList;
  
  /**
   * Maps outline nodes to ranges in document
   */
  private WSXMLTextNodeRange[] currentOutlineRanges; 
  
  /**
   * The current text page
   */
  private WSXMLTextEditorPage currentTextPage;
  
  /**
   * Disable CaretListener when we select from the CaretListener.
   */
  private boolean enableCaretListener = true;
  
  /**
   * @see WorkspaceAccessPluginExtension#applicationStarted
(ro.sync.exml.workspace.api.standalone.StandalonePluginWorkspace)
   */
  @Override
  public void applicationStarted
(final StandalonePluginWorkspace pluginWorkspaceAccess) {
    pluginWorkspaceAccess.addViewComponentCustomizer
(new ViewComponentCustomizer() {
      /**
       * @see ViewComponentCustomizer#customizeView
(ro.sync.exml.workspace.api.standalone.ViewInfo)
       */
      @Override
      public void customizeView(ViewInfo viewInfo) {
        if(
            //The view ID defined in the "plugin.xml"
            "SampleWorkspaceAccessID".equals(viewInfo.getViewID())) {
          customOutlineList = new JList();
          //Render the content in the Outline.
          customOutlineList.setCellRenderer(new DefaultListCellRenderer() {
       /**
        * @see javax.swing.DefaultListCellRenderer#getListCellRendererComponent
(javax.swing.JList, java.lang.Object, int, boolean, boolean)
        */
      @Override
      public Component getListCellRendererComponent
(JList<?> list, Object value, int index,
          boolean isSelected, boolean cellHasFocus) {
        JLabel label = (JLabel) super.getListCellRendererComponent
(list, value, index, isSelected, cellHasFocus);
        String val = null;
        if(value instanceof Element) {
          Element element = ((Element)value);
          val = element.getNodeName();
          if(!"".equals(element.getAttribute("startnumber"))) {
            val += " " + "'" + element.getAttribute("startnumber") + "'";
          }
          NodeList titles = element.getElementsByTagName("title");
          if(titles.getLength() > 0) {
            val += " \"" + titles.item(0).getTextContent() + "\"";
         }
       }
        label.setText(val);
        return label;
      }
    });
    //When we click a node, select it in the text page.
    customOutlineList.addMouseListener(new MouseAdapter() {
     @Override
     public void mouseClicked(MouseEvent e) {
       if(SwingUtilities.isLeftMouseButton(e) && e.getClickCount() == 2) {
          int sel = customOutlineList.getSelectedIndex();
          enableCaretListener = false;
         try {
          currentTextPage.select(currentTextPage.getOffsetOfLineStart
(currentOutlineRanges[sel].getStartLine()) + 
currentOutlineRanges[sel].getStartColumn() - 1, 
            currentTextPage.getOffsetOfLineStart
(currentOutlineRanges[sel].getEndLine()) + 
currentOutlineRanges[sel].getEndColumn());
          } catch (BadLocationException e1) {
           e1.printStackTrace();
         }
          enableCaretListener = true;
        }
      }
    });
     viewInfo.setComponent(new JScrollPane(customOutlineList));
     viewInfo.setTitle("Custom Outline");
  } 
 }
}); 
    
pluginWorkspaceAccess.addEditorChangeListener(new WSEditorChangeListener() {
  /**
  * @see WSEditorChangeListener#editorOpened(java.net.URL)
  */
  @Override
  public void editorOpened(URL editorLocation) {
   //An editor was opened
   WSEditor editorAccess = pluginWorkspaceAccess.getEditorAccess
(editorLocation, StandalonePluginWorkspace.MAIN_EDITING_AREA);
        if(editorAccess != null) {
          WSEditorPage currentPage = editorAccess.getCurrentPage();
          if(currentPage instanceof WSXMLTextEditorPage) {
            //User editing in Text mode an open XML document.
            final WSXMLTextEditorPage xmlTP = (WSXMLTextEditorPage) currentPage;
            //Reconfigure outline on each change.
            xmlTP.getDocument().addDocumentListener(new DocumentListener() {
              @Override
              public void removeUpdate(DocumentEvent e) {
                reconfigureOutline(xmlTP);
              }
              @Override
              public void insertUpdate(DocumentEvent e) {
                reconfigureOutline(xmlTP);
              }
              @Override
              public void changedUpdate(DocumentEvent e) {
                reconfigureOutline(xmlTP);
              }
            });
            JTextArea textComponent = (JTextArea) xmlTP.getTextComponent();
            textComponent.addCaretListener(new CaretListener() {
              @Override
              public void caretUpdate(CaretEvent e) {
              if(currentOutlineRanges != null && currentTextPage != null && 
enableCaretListener) {
                  enableCaretListener = false;
                  //Find the node to select in the outline.
                  try {
                    int line = xmlTP.getLineOfOffset(e.getDot());
                    for (int i = currentOutlineRanges.length - 1; i >= 0; i--) {
              if(line > currentOutlineRanges[i].getStartLine() && 
line < currentOutlineRanges[i].getEndLine()) {
                        customOutlineList.setSelectedIndex(i);
                        break;
                      }
                    }
                  } catch (BadLocationException e1) {
                    e1.printStackTrace();
                  }
                  enableCaretListener = true;
                }
              }
            });
          }
        }
      }
      /**
       * @see WSEditorChangeListener#editorActivated(java.net.URL)
       */
      @Override
      public void editorActivated(URL editorLocation) {
        //An editor was selected, reconfigure the common outline
        WSEditor editorAccess = pluginWorkspaceAccess.getEditorAccess
(editorLocation, StandalonePluginWorkspace.MAIN_EDITING_AREA);
        if(editorAccess != null) {
          WSEditorPage currentPage = editorAccess.getCurrentPage();
          if(currentPage instanceof WSXMLTextEditorPage) {
            //User editing in Text mode an open XML document.
            WSXMLTextEditorPage xmlTP = (WSXMLTextEditorPage) currentPage;
            reconfigureOutline(xmlTP);
          }
        }
      }
    }, StandalonePluginWorkspace.MAIN_EDITING_AREA);
  }
  
  /**
   * Reconfigure the outline
   * 
   * @param xmlTP The XML Text page.
   */
  protected void reconfigureOutline(final WSXMLTextEditorPage xmlTP) {
    try {
      //These are DOM nodes.
      Object[] evaluateXPath = xmlTP.evaluateXPath("//doc | //sec");
      //These are the ranges each node takes in the document.
      currentOutlineRanges = xmlTP.findElementsByXPath("//doc | //sec");
      currentTextPage = xmlTP;
      DefaultListModel listModel = new DefaultListModel();
      if(evaluateXPath != null) {
        for (int i = 0; i < evaluateXPath.length; i++) { 
          listModel.addElement(evaluateXPath[i]);
        }
      }
      customOutlineList.setModel(listModel);
    } catch(XPathException ex) {
      ex.printStackTrace();
    }
  }

  /**
   * @see WorkspaceAccessPluginExtension#applicationClosing()
   */
  @Override
  public boolean applicationClosing() {
    return true;
  }
}