This bug was introduced by the fix for
4855207 [Fix for 4250864: Low performance in JTextPane when paragraph has a lot of text]

Run TestAlignment

1. justify first paragraph.
2. move cursor to the begining of the document
3. pres Enter multiple times
4. At some point paragraph is not justified anymore.
It happens because GlyphView in the paragraph is not children of
ParagraphView.Row but children of LogicalView instead


-- TestAlignment.java --
//test from the bug report for 4263904
import javax.swing.text.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class TestAlignment extends JFrame
{
  private JTextPane myTextPane;
  private SimpleAttributeSet sas;
  private StyledDocument theDocument;

  public TestAlignment()
  {
    super();
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize( 500, 500);
    getContentPane().setLayout( new GridLayout( 1, 2));

    myTextPane = new JTextPane();
    myTextPane.setSize( 250, 250);
    getContentPane().add( myTextPane);
    myTextPane.setText( "A long line of text for testing alignment");
    //myTextPane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
    sas = new SimpleAttributeSet();

    JButton leftAlignButton = new JButton( "left");
    JButton rightAlignButton = new JButton( "right");
    JButton centreButton = new JButton( "centered");
    JButton justifyButton = new JButton( "justified");

    JPanel buttonPanel = new JPanel();

    leftAlignButton.addActionListener( new ActionListener() {
      public void actionPerformed( ActionEvent e)
      {
        StyleConstants.setAlignment( sas, StyleConstants.ALIGN_LEFT);
        myTextPane.setParagraphAttributes( sas, false);

        myTextPane.repaint();
      }
    });

    rightAlignButton.addActionListener( new ActionListener() {
      public void actionPerformed( ActionEvent e)
      {
        StyleConstants.setAlignment( sas, StyleConstants.ALIGN_RIGHT);
        myTextPane.setParagraphAttributes( sas, false);

        myTextPane.repaint();
      }
    });

    centreButton.addActionListener( new ActionListener() {
      public void actionPerformed( ActionEvent e)
      {
        StyleConstants.setAlignment( sas, StyleConstants.ALIGN_CENTER);
        myTextPane.setParagraphAttributes( sas, false);

        myTextPane.repaint(); }
    });

    justifyButton.addActionListener( new ActionListener() {
      public void actionPerformed( ActionEvent e)
      {
        StyleConstants.setAlignment( sas, StyleConstants.ALIGN_JUSTIFIED);
        myTextPane.setParagraphAttributes( sas, false);

        myTextPane.repaint();
      }
    });

    buttonPanel.add( leftAlignButton);
    buttonPanel.add( centreButton);
    buttonPanel.add( rightAlignButton);
    buttonPanel.add( justifyButton);

    getContentPane().add( buttonPanel);
  }

  public static void main( String args[])
  {
    TestAlignment myFrame = new TestAlignment();
    myFrame.show();
  }
}
-----