Problem with text formatting in JTextPane/DefaultStyledDocument using setCharacterAttributes()

HighlightedTextArea.java

package testing;

import testing.ObjectExplorer;
import java.awt.Font;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.Collections;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JTextPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.Element;

public final class HighlightedTextArea extends JTextPane {

    private final List<Object> highlights = new ArrayList<>();

    private Logger logger;

    public HighlightedTextArea() {
        super();

        logger = Logger.getLogger(HighlightedTextArea.class.getName());

        setFont(new Font("Courier New", Font.PLAIN, 12));
        setDocument(new myStylizedDocument());//Syntax highlighting

        addLink();
    }

    @Override
    public String getText() {
        try {
            return getDocument().getText(0, getDocument().getLength());
        } catch (BadLocationException ex) {
            Logger.getLogger(HighlightedTextArea.class.getName()).log(Level.SEVERE, null, ex);
        }

        return null;
    }

    @Override
    public void setText(String t) {

        logger.log(Level.INFO,
                "Setting text (to a new document)");
        try {
            logger.log(Level.INFO,
                    "Old contents: " + getDocument().getText(0, getDocument().getLength()));
        } catch (Exception e) {
            logger.log(Level.INFO,
                    "Couldn't get contents!");
        }
        setDocument(new myStylizedDocument());
        try {
            logger.log(Level.INFO,
                    "New contents: " + getDocument().getText(0, getDocument().getLength()));
        } catch (Exception e) {
            logger.log(Level.INFO,
                    "Couldn't get contents!");
        }
        super.setText(t);

        logger.log(Level.INFO,
                "Text has been set.");

    }

    private void addLink() {
        MouseAdapter adapter = new MouseAdapter() {

            @Override
            public void mousePressed(MouseEvent e) {
                if (e.getClickCount() == 2) {
                    logger.log(Level.INFO,
                        "Received mouse click for URL");
                    ObjectExplorer.INSTANCE.update();
                }
            }

        };
        this.addMouseListener(adapter);
    }

}

myStylizedDocument.java

package testing;

import java.awt.Color;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultStyledDocument;
import javax.swing.text.MutableAttributeSet;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;
import java.util.logging.Logger;
import java.util.logging.Level;

public class myStylizedDocument extends DefaultStyledDocument {

    private final MutableAttributeSet normal;
    private final MutableAttributeSet quote;

    private Logger logger;

    public myStylizedDocument() {

        logger = Logger.getLogger(myStylizedDocument.class.getName());

        normal = new SimpleAttributeSet();
        StyleConstants.setForeground(normal, Color.BLACK);

        quote = new SimpleAttributeSet();
        StyleConstants.setForeground(quote, Color.RED);
    }

    /*
     * Override to apply syntax highlighting after the document has been updated
     */
    @Override
    public void insertString(int offset, String str, AttributeSet a) throws BadLocationException {
        super.insertString(offset, str, a);
        Logger.getLogger(myStylizedDocument.class.getName()).log(
                Level.INFO,
                "In insertString, about to apply highlighting");

        // Hardcoding this syntax highlight for simplicity's sake
        String content = getText(0, getLength());
        int firstIdx = content.indexOf("'");
        int secondIdx = content.lastIndexOf("'");
        if (firstIdx != -1 && secondIdx != -1) {
            setCharacterAttributes(firstIdx, secondIdx-firstIdx, quote, false);
        }
    }

}

ObjectExplorer.java

package testing;

import testing.HighlightedTextArea;
import java.awt.BorderLayout;

public final class ObjectExplorer extends javax.swing.JFrame {

    public static ObjectExplorer INSTANCE = null;
    private final HighlightedTextArea textElement;

    private int counter;

    /**
     * Creates new form DumpFrame
     */
    public ObjectExplorer() {
        initComponents();
        INSTANCE = this;
        counter = 0;

        textElement = new HighlightedTextArea();
        textElement.setEditable(false);
        jPanel1.setLayout(new BorderLayout());
        jPanel1.add(textElement);

        // Pretend to have some data.
        setText("(\n    ALinkToSee = AttributeType'GD_Foo_Bar.Baz.Frotz'\n)\n");

    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {

        /* Create and display the form */
        new ObjectExplorer().setVisible(true);
    }

    public void update() {
        counter++;
        setText(String.format(
                "(\n    NewFakeData = AnotherAttribute'GD_Omg_Wtf.NotReal.Stuff%d'\n)\n",
                counter));
    }

    private void setText(String text) {
        textElement.setText(text);
    }

    @Override
    public void dispose() {
        INSTANCE = null;
        super.dispose();
        System.exit(0);
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();

        setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
        setTitle("Object Explorer");

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 977, Short.MAX_VALUE)
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 537, Short.MAX_VALUE)
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(13, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>//GEN-END:initComponents

    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JPanel jPanel1;
    // End of variables declaration//GEN-END:variables

}