Strange text wrapping with styled text in JTextPane with Java 7

Question

I have two different editors using JTextPane with strange bugs in Java 7 that did not occur with the previous JVM versions. It happens with long lines containing styled text

Answer 1

Investigated this. The reason is breakSpots caching. Looks like LabelView stores them and don't recalculate offsets on previos text edit. If I reset them manually the bug does not happen.

A workaround (very dirty because of private breakSpots fields) is following

import java.awt.Dimension;
import java.lang.reflect.Field;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;

public class BugWrapJava7 {

    private JFrame frame = new JFrame();
    private JTextPane jtp;
    private StyledDocument doc;

    public BugWrapJava7() {
        jtp = new JTextPane();
        jtp.setEditorKit(new MyStyledEditorKit());
        jtp.setText("\ntype some text in the above empty line and check the wrapping behavior");
        doc = jtp.getStyledDocument();
        doc.addDocumentListener(new DocumentListener() {

            public void insertUpdate(DocumentEvent e) {
                insert();
            }

            public void removeUpdate(DocumentEvent e) {
                insert();
            }

            public void changedUpdate(DocumentEvent e) {
                insert();
            }

            public void insert() {
                SwingUtilities.invokeLater(new Runnable() {

                    public void run() {
                        Style defaultStyle = jtp.getStyle(StyleContext.DEFAULT_STYLE);
                        doc.setCharacterAttributes(0, doc.getLength(), defaultStyle, false);
                    }
                });
            }
        });
        JScrollPane scroll = new JScrollPane(jtp);
        scroll.setPreferredSize(new Dimension(200, 200));
        frame.add(scroll);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                BugWrapJava7 bugWrapJava7 = new BugWrapJava7();
            }
        });
    }
}

class MyStyledEditorKit extends StyledEditorKit {
    private MyFactory factory;

    public ViewFactory getViewFactory() {
        if (factory == null) {
            factory = new MyFactory();
        }
        return factory;
    }
}

class MyFactory implements ViewFactory {
    public View create(Element elem) {
        String kind = elem.getName();
        if (kind != null) {
            if (kind.equals(AbstractDocument.ContentElementName)) {
                return new MyLabelView(elem);
            } else if (kind.equals(AbstractDocument.ParagraphElementName)) {
                return new ParagraphView(elem);
            } else if (kind.equals(AbstractDocument.SectionElementName)) {
                return new BoxView(elem, View.Y_AXIS);
            } else if (kind.equals(StyleConstants.ComponentElementName)) {
                return new ComponentView(elem);
            } else if (kind.equals(StyleConstants.IconElementName)) {
                return new IconView(elem);
            }
        }

        // default to text display
        return new LabelView(elem);
    }
}

class MyLabelView extends LabelView {
    public MyLabelView(Element elem) {
        super(elem);
    }
    public View breakView(int axis, int p0, float pos, float len) {
        if (axis == View.X_AXIS) {
            resetBreakSpots();
        }
        return super.breakView(axis, p0, pos, len);
    }

    private void resetBreakSpots() {
        try {
            // HACK the breakSpots private fields
            Field f=GlyphView.class.getDeclaredField("breakSpots");
            f.setAccessible(true);
            f.set(this, null);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

Less hack without the reflection. Based on usual reset of breakSpots on model change.

class MyLabelView extends LabelView {

    boolean isResetBreakSpots=false;

    public MyLabelView(Element elem) {
        super(elem);
    }
    public View breakView(int axis, int p0, float pos, float len) {
        if (axis == View.X_AXIS) {
            resetBreakSpots();
        }
        return super.breakView(axis, p0, pos, len);
    }

    private void resetBreakSpots() {
        isResetBreakSpots=true;
        removeUpdate(null, null, null);
        isResetBreakSpots=false;

//        try {
//            Field f=GlyphView.class.getDeclaredField("breakSpots");
//            f.setAccessible(true);
//            f.set(this, null);
//        } catch (Exception e) {
//            e.printStackTrace();
//        }
    }

    public void removeUpdate(DocumentEvent e, Shape a, ViewFactory f) {
        super.removeUpdate(e, a, f);
    }

    public void preferenceChanged(View child, boolean width, boolean height) {
        if (!isResetBreakSpots) {
            super.preferenceChanged(child, width, height);
        }
    }
}

UPDATE: This one fixes TextSamplerDemo as well. I reset all spots for all labels views.

class MyStyledEditorKit extends StyledEditorKit {
    private MyFactory factory;

    public ViewFactory getViewFactory() {
        if (factory == null) {
            factory = new MyFactory();
        }
        return factory;
    }
}

class MyFactory implements ViewFactory {
    public View create(Element elem) {
        String kind = elem.getName();
        if (kind != null) {
            if (kind.equals(AbstractDocument.ContentElementName)) {
                return new MyLabelView(elem);
            } else if (kind.equals(AbstractDocument.ParagraphElementName)) {
                return new MyParagraphView(elem);
            } else if (kind.equals(AbstractDocument.SectionElementName)) {
                return new BoxView(elem, View.Y_AXIS);
            } else if (kind.equals(StyleConstants.ComponentElementName)) {
                return new ComponentView(elem);
            } else if (kind.equals(StyleConstants.IconElementName)) {
                return new IconView(elem);
            }
        }

        // default to text display
        return new LabelView(elem);
    }
}

class MyParagraphView extends ParagraphView {

    public MyParagraphView(Element elem) {
        super(elem);
    }
public void removeUpdate(DocumentEvent e, Shape a, ViewFactory f) {
    super.removeUpdate(e, a, f);
    resetBreakSpots();
}
public void insertUpdate(DocumentEvent e, Shape a, ViewFactory f) {
    super.insertUpdate(e, a, f);
    resetBreakSpots();
}

private void resetBreakSpots() {
    for (int i=0; i