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Java > Open Source Codes > org > eclipse > text > edits > UndoCollector


1 /*******************************************************************************
2  * Copyright (c) 2000, 2006 IBM Corporation and others.
3  * All rights reserved. This program and the accompanying materials
4  * are made available under the terms of the Eclipse Public License v1.0
5  * which accompanies this distribution, and is available at
6  * http://www.eclipse.org/legal/epl-v10.html
7  *
8  * Contributors:
9  * IBM Corporation - initial API and implementation
10  *******************************************************************************/
11 package org.eclipse.text.edits;
12
13 import org.eclipse.core.runtime.Assert;
14
15 import org.eclipse.jface.text.BadLocationException;
16 import org.eclipse.jface.text.DocumentEvent;
17 import org.eclipse.jface.text.IDocument;
18 import org.eclipse.jface.text.IDocumentListener;
19
20
21 class UndoCollector implements IDocumentListener {
22
23     protected UndoEdit undo;
24     private int fOffset;
25     private int fLength;
26     
27     /**
28      * @since 3.1
29      */
30     private String JavaDoc fLastCurrentText;
31
32     public UndoCollector(TextEdit root) {
33         fOffset= root.getOffset();
34         fLength= root.getLength();
35     }
36
37     public void connect(IDocument document) {
38         document.addDocumentListener(this);
39         undo= new UndoEdit();
40     }
41
42     public void disconnect(IDocument document) {
43         if (undo != null) {
44             document.removeDocumentListener(this);
45             undo.defineRegion(fOffset, fLength);
46         }
47     }
48
49     public void documentChanged(DocumentEvent event) {
50         fLength+= getDelta(event);
51     }
52
53     private static int getDelta(DocumentEvent event) {
54         String JavaDoc text= event.getText();
55         return text == null ? -event.getLength() : (text.length() - event.getLength());
56     }
57
58     public void documentAboutToBeChanged(DocumentEvent event) {
59         int offset= event.getOffset();
60         int currentLength= event.getLength();
61         String JavaDoc currentText= null;
62         try {
63             currentText= event.getDocument().get(offset, currentLength);
64         } catch (BadLocationException cannotHappen) {
65             Assert.isTrue(false, "Can't happen"); //$NON-NLS-1$
66 }
67         
68         /*
69          * see https://bugs.eclipse.org/bugs/show_bug.cgi?id=93634
70          * If the same string is replaced on many documents (e.g. rename
71          * package), the size of the undo can be reduced by using the same
72          * String instance in all edits, instead of using the unique String
73          * returned from IDocument.get(int, int).
74          */
75         if (fLastCurrentText != null && fLastCurrentText.equals(currentText))
76             currentText= fLastCurrentText;
77         else
78             fLastCurrentText= currentText;
79
80         String JavaDoc newText= event.getText();
81         undo.add(new ReplaceEdit(offset, newText != null ? newText.length() : 0, currentText));
82     }
83 }
84
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