gistfile1.txt

/*
 * SK's Minecraft Launcher
 * Copyright (C) 2010-2014 Albert Pham <http://www.sk89q.com> and contributors
 * Please see LICENSE.txt for license information.
 */

package com.skcraft.launcher.util;

import javax.swing.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.Element;

/**
 * From http://tips4java.wordpress.com/2008/10/15/limit-lines-in-document/
 * 
 * @author Rob Camick
 */
public class LimitLinesDocumentListener implements DocumentListener {
    private int maximumLines;
    private boolean isRemoveFromStart;

    /**
     * Specify the number of lines to be stored in the Document. Extra lines
     * will be removed from the start or end of the Document, depending on
     * the boolean value specified.
     * 
     * @param maximumLines number of lines
     * @param isRemoveFromStart true to remove from the start
     */
    public LimitLinesDocumentListener(int maximumLines,
                                      boolean isRemoveFromStart) {
        setLimitLines(maximumLines);
        this.isRemoveFromStart = isRemoveFromStart;
    }

    /**
     * Set the maximum number of lines to be stored in the Document
     * 
     * @param maximumLines number of lines
     */
    public void setLimitLines(int maximumLines) {
        if (maximumLines < 1) {
            throw new IllegalArgumentException("Maximum lines must be greater than 0");
        }

        this.maximumLines = maximumLines;
    }

    @Override
    public void insertUpdate(final DocumentEvent e) {
        // Changes to the Document can not be done within the listener
        // so we need to add the processing to the end of the EDT

        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                removeLines(e);
            }
        });
    }

    @Override
    public void removeUpdate(DocumentEvent e) {
    }

    @Override
    public void changedUpdate(DocumentEvent e) {
    }

    private void removeLines(DocumentEvent e) {
        // The root Element of the Document will tell us the total number
        // of line in the Document.

        Document document = e.getDocument();
        Element root = document.getDefaultRootElement();
	int excess = root.getElementCount() - maximumLines;
	if (excess > 0) {
            if (isRemoveFromStart) {
                removeFromStart(document, root, excess);
            } else {
                removeFromEnd(document, root, excess);
            }
        }
    }

    private void removeFromStart(Document document, Element root, int excess) {
        Element line = root.getElement(excess - 1);
        int start = line.getStartOffset();
        int end = line.getEndOffset();

        try {
            document.remove(0, end);
	    System.out.printf("rFS: excess %d, element is %d-%d, new count %d/%d\n", excess, start, end, root.getElementCount(), maximumLines);
        } catch (BadLocationException ble) {
	    System.out.printf("rFS: excess %d, range %d-%d failed\n", excess, start, end);
            System.out.println(ble);
        }
    }

    private void removeFromEnd(Document document, Element root, int excess) {
        // We use start minus 1 to make sure we remove the newline
        // character of the previous line

        Element line = root.getElement(root.getElementCount() - excess);
        int start = line.getStartOffset();
        int end = line.getEndOffset();

        try {
            document.remove(start - 1, end - start);
        } catch (BadLocationException ble) {
            System.out.println(ble);
        }
    }
}