org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/actions/IndentAction.java - jdt/eclipse.jdt.ui - Git at Google

 /*******************************************************************************
  * Copyright (c) 2000, 2003 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Common Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/cpl-v10.html
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.jdt.internal.ui.actions;

 import java.util.ResourceBundle;

 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.Status;

 import org.eclipse.swt.custom.BusyIndicator;
 import org.eclipse.swt.widgets.Display;

 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.jface.viewers.ISelectionProvider;

 import org.eclipse.jface.text.Assert;
 import org.eclipse.jface.text.BadLocationException;
 import org.eclipse.jface.text.DocumentCommand;
 import org.eclipse.jface.text.IDocument;
 import org.eclipse.jface.text.IRegion;
 import org.eclipse.jface.text.IRewriteTarget;
 import org.eclipse.jface.text.ITextSelection;
 import org.eclipse.jface.text.ITypedRegion;
 import org.eclipse.jface.text.Position;
 import org.eclipse.jface.text.TextSelection;
 import org.eclipse.jface.text.TextUtilities;
 import org.eclipse.jface.text.source.ISourceViewer;

 import org.eclipse.ui.IEditorInput;
 import org.eclipse.ui.texteditor.IDocumentProvider;
 import org.eclipse.ui.texteditor.ITextEditor;
 import org.eclipse.ui.texteditor.ITextEditorExtension3;
 import org.eclipse.ui.texteditor.TextEditorAction;

 import org.eclipse.jdt.core.JavaCore;

 import org.eclipse.jdt.ui.PreferenceConstants;

 import org.eclipse.jdt.internal.ui.JavaPlugin;
 import org.eclipse.jdt.internal.ui.javaeditor.JavaEditor;
 import org.eclipse.jdt.internal.ui.text.IJavaPartitions;
 import org.eclipse.jdt.internal.ui.text.JavaHeuristicScanner;
 import org.eclipse.jdt.internal.ui.text.JavaIndenter;
 import org.eclipse.jdt.internal.ui.text.javadoc.JavaDocAutoIndentStrategy;


 /**
  * Indents a line or range of lines in a Java document to its correct position. No complete
  * AST must be present, the indentation is computed using heuristics. The algorith used is fast for
  * single lines, but does not store any information and therefore not so efficient for large line
  * ranges.
  *
  * @see org.eclipse.jdt.internal.ui.text.JavaHeuristicScanner
  * @see org.eclipse.jdt.internal.ui.text.JavaIndenter
  * @since 3.0
  */
 public class IndentAction extends TextEditorAction {

 	/** The caret offset after an indent operation. */
 	private int fCaretOffset;

 	/**
 	 * Whether this is the action invoked by TAB. When <code>true</code>, indentation behaves
 	 * differently to accomodate normal TAB operation.
 	 */
 	private final boolean fIsTabAction;

 	/**
 	 * Creates a new instance.
 	 *
 	 * @param bundle the resource bundle
 	 * @param prefix the prefix to use for keys in <code>bundle</code>
 	 * @param editor the text editor
 	 */
 	public IndentAction(ResourceBundle bundle, String prefix, ITextEditor editor, boolean isTabAction) {
 		super(bundle, prefix, editor);
 		fIsTabAction= isTabAction;
 	}

 	/*
 	 * @see org.eclipse.jface.action.Action#run()
 	 */
 	public void run() {
 		// update has been called by the framework
 		if (!isEnabled() || !validateEditorInputState())
 			return;

 		ITextSelection selection= getSelection();
 		final IDocument document= getDocument();

 		if (document != null) {

 			final int offset= selection.getOffset();
 			final int length= selection.getLength();
 			final Position end= new Position(offset + length);
 			final int firstLine, nLines;
 			fCaretOffset= -1;

 			try {
 				document.addPosition(end);
 				firstLine= document.getLineOfOffset(offset);
 				// check for marginal (zero-length) lines
 				int minusOne= length == 0 ? 0 : 1;
 				nLines= document.getLineOfOffset(offset + length - minusOne) - firstLine + 1;
 			} catch (BadLocationException e) {
 				// will only happen on concurrent modification
 				JavaPlugin.log(new Status(IStatus.ERROR, JavaPlugin.getPluginId(), IStatus.OK, "", e)); //$NON-NLS-1$
 				return;
 			}

 			Runnable runnable= new Runnable() {
 				public void run() {
 					IRewriteTarget target= (IRewriteTarget)getTextEditor().getAdapter(IRewriteTarget.class);
 					if (target != null) {
 						target.beginCompoundChange();
 						target.setRedraw(false);
 					}

 					try {
 						JavaHeuristicScanner scanner= new JavaHeuristicScanner(document);
 						JavaIndenter indenter= new JavaIndenter(document, scanner);
 						boolean hasChanged= false;
 						for (int i= 0; i < nLines; i++) {
 							hasChanged |= indentLine(document, firstLine + i, offset, indenter, scanner);
 						}

 						// update caret position: move to new position when indenting just one line
 						// keep selection when indenting multiple
 						int newOffset, newLength;
 						if (fIsTabAction) {
 							newOffset= fCaretOffset;
 							newLength= 0;
 						} else if (nLines > 1) {
 							newOffset= offset;
 							newLength= end.getOffset() - offset;
 						} else {
 							newOffset= fCaretOffset;
 							newLength= 0;
 						}

 						// always reset the selection if anything was replaced
 						// but not when we had a singleline nontab invocation
 						if (newOffset != -1 && (hasChanged || newOffset != offset || newLength != length))
 							selectAndReveal(newOffset, newLength);

 						document.removePosition(end);
 					} catch (BadLocationException e) {
 						// will only happen on concurrent modification
 						JavaPlugin.log(new Status(IStatus.ERROR, JavaPlugin.getPluginId(), IStatus.OK, "ConcurrentModification in IndentAction", e)); //$NON-NLS-1$

 					} finally {

 						if (target != null) {
 							target.endCompoundChange();
 							target.setRedraw(true);
 						}
 					}
 				}
 			};

 			if (nLines > 50) {
 				Display display= getTextEditor().getEditorSite().getWorkbenchWindow().getShell().getDisplay();
 				BusyIndicator.showWhile(display, runnable);
 			} else
 				runnable.run();

 		}
 	}

 	/**
 	 * Selects the given range on the editor.
 	 *
 	 * @param newOffset the selection offset
 	 * @param newLength the selection range
 	 */
 	private void selectAndReveal(int newOffset, int newLength) {
 		Assert.isTrue(newOffset >= 0);
 		Assert.isTrue(newLength >= 0);
 		ITextEditor editor= getTextEditor();
 		if (editor instanceof JavaEditor) {
 			ISourceViewer viewer= ((JavaEditor)editor).getViewer();
 			if (viewer != null)
 				viewer.setSelectedRange(newOffset, newLength);
 		} else
 			// this is too intrusive, but will never get called anyway
 			getTextEditor().selectAndReveal(newOffset, newLength);

 	}

 	/**
 	 * Indents a single line using the java heuristic scanner. Javadoc and multiline comments are
 	 * indented as specified by the <code>JavaDocAutoIndentStrategy</code>.
 	 *
 	 * @param document the document
 	 * @param line the line to be indented
 	 * @param caret the caret position
 	 * @param indenter the java indenter
 	 * @param scanner the heuristic scanner
 	 * @return <code>true</code> if <code>document</code> was modified, <code>false</code> otherwise
 	 * @throws BadLocationException if the document got changed concurrently
 	 */
 	private boolean indentLine(IDocument document, int line, int caret, JavaIndenter indenter, JavaHeuristicScanner scanner) throws BadLocationException {
 		IRegion currentLine= document.getLineInformation(line);
 		int offset= currentLine.getOffset();

 		String indent= null;
 		if (offset < document.getLength()) {
 			ITypedRegion partition= TextUtilities.getPartition(document, IJavaPartitions.JAVA_PARTITIONING, offset);
 			String type= partition.getType();
 			if (partition.getOffset() < offset
 					&& type.equals(IJavaPartitions.JAVA_DOC)
 					|| type.equals(IJavaPartitions.JAVA_MULTI_LINE_COMMENT)) {

 				// TODO this is a hack
 				// what I want to do
 //				new JavaDocAutoIndentStrategy().indentLineAtOffset(document, offset);
 //				return;

 				int start= 0;
 				if (line > 0) {

 					IRegion previousLine= document.getLineInformation(line - 1);
 					start= previousLine.getOffset() + previousLine.getLength();
 				}

 				DocumentCommand command= new DocumentCommand() {};
 				command.text= "\n"; //$NON-NLS-1$
 				command.offset= start;
 				new JavaDocAutoIndentStrategy(IJavaPartitions.JAVA_PARTITIONING).customizeDocumentCommand(document, command);
 				int i= command.text.indexOf('*');
 				if (i != -1)
 					indent= command.text.substring(1, i);
 				else
 					indent= command.text.substring(1);
 			}
 		}

 		// standard java indentation
 		if (indent == null) {
 			StringBuffer computed= indenter.computeIndentation(offset);
 			if (computed != null)
 				indent= computed.toString();
 			else
 				indent= new String();
 		}

 		// change document:
 		// get current white space
 		int lineLength= currentLine.getLength();
 		int end= scanner.findNonWhitespaceForwardInAnyPartition(offset, offset + lineLength);
 		if (end == JavaHeuristicScanner.NOT_FOUND)
 			end= offset + lineLength;
 		int length= end - offset;
 		String currentIndent= document.get(offset, length);

 		// if we are right before the text start / line end, and already after the insertion point
 		// then just insert a tab.
 		if (fIsTabAction && caret == end && whiteSpaceLength(currentIndent) >= whiteSpaceLength(indent)) {
 			String tab= getTabEquivalent();
 			document.replace(caret, 0, tab);
 			fCaretOffset= caret + tab.length();
 			return true;
 		}

 		// set the caret offset so it can be used when setting the selection
 		if (caret >= offset && caret <= end)
 			fCaretOffset= offset + indent.length();
 		else
 			fCaretOffset= -1;

 		// only change the document if it is a real change
 		if (!indent.equals(currentIndent)) {
 			document.replace(offset, length, indent);
 			return true;
 		} else
 			return false;
 	}

 	/**
 	 * Returns the size in characters of a string. All characters count one, tabs count the editor's
 	 * preference for the tab display
 	 *
 	 * @param indent the string to be measured.
 	 * @return
 	 */
 	private int whiteSpaceLength(String indent) {
 		if (indent == null)
 			return 0;
 		else {
 			int size= 0;
 			int l= indent.length();
 			int tabSize= JavaPlugin.getDefault().getPreferenceStore().getInt(PreferenceConstants.EDITOR_TAB_WIDTH);

 			for (int i= 0; i < l; i++)
 				size += indent.charAt(i) == '\t' ? tabSize : 1;
 			return size;
 		}
 	}

 	/**
 	 * Returns a tab equivalent, either as a tab character or as spaces, depending on the editor and
 	 * formatter preferences.
 	 *
 	 * @return a string representing one tab in the editor, never <code>null</code>
 	 */
 	private String getTabEquivalent() {
 		String tab;
 		if (JavaPlugin.getDefault().getPreferenceStore().getBoolean(PreferenceConstants.EDITOR_SPACES_FOR_TABS)) {
 			int size= JavaCore.getPlugin().getPluginPreferences().getInt(JavaCore.FORMATTER_TAB_SIZE);
 			StringBuffer buf= new StringBuffer();
 			for (int i= 0; i< size; i++)
 				buf.append(' ');
 			tab= buf.toString();
 		} else
 			tab= "\t"; //$NON-NLS-1$

 		return tab;
 	}

 	/**
 	 * Returns the editor's selection provider.
 	 *
 	 * @return the editor's selection provider or <code>null</code>
 	 */
 	private ISelectionProvider getSelectionProvider() {
 		ITextEditor editor= getTextEditor();
 		if (editor != null) {
 			return editor.getSelectionProvider();
 		}
 		return null;
 	}

 	/*
 	 * @see org.eclipse.ui.texteditor.IUpdate#update()
 	 */
 	public void update() {
 		super.update();

 		if (isEnabled())
 			if (fIsTabAction)
 				setEnabled(canModifyEditor() && isSmartMode() && isValidSelection());
 			else
 				setEnabled(canModifyEditor() && !getSelection().isEmpty());
 	}

 	/**
 	 * Returns if the current selection is valid, i.e. whether it is empty and the caret in the
 	 * whitespace at the start of a line, or covers multiple lines.
 	 *
 	 * @return <code>true</code> if the selection is valid for an indent operation
 	 */
 	private boolean isValidSelection() {
 		ITextSelection selection= getSelection();
 		if (selection.isEmpty())
 			return false;

 		int offset= selection.getOffset();
 		int length= selection.getLength();

 		IDocument document= getDocument();
 		if (document == null)
 			return false;

 		try {
 			IRegion firstLine= document.getLineInformationOfOffset(offset);
 			int lineOffset= firstLine.getOffset();

 			// either the selection has to be empty and the caret in the WS at the line start
 			// or the selection has to extend over multiple lines
 			if (length == 0)
 				return document.get(lineOffset, offset - lineOffset).trim().length() == 0;
 			else
 //				return lineOffset + firstLine.getLength() < offset + length;
 				return false; // only enable for empty selections for now

 		} catch (BadLocationException e) {
 		}

 		return false;
 	}

 	/**
 	 * Returns the smart preference state.
 	 *
 	 * @return <code>true</code> if smart mode is on, <code>false</code> otherwise
 	 */
 	private boolean isSmartMode() {
 		ITextEditor editor= getTextEditor();

 		if (editor instanceof ITextEditorExtension3)
 			return ((ITextEditorExtension3) editor).getInsertMode() == ITextEditorExtension3.SMART_INSERT;

 		return false;
 	}

 	/**
 	 * Returns the document currently displayed in the editor, or <code>null</code> if none can be
 	 * obtained.
 	 *
 	 * @return the current document or <code>null</code>
 	 */
 	private IDocument getDocument() {

 		ITextEditor editor= getTextEditor();
 		if (editor != null) {

 			IDocumentProvider provider= editor.getDocumentProvider();
 			IEditorInput input= editor.getEditorInput();
 			if (provider != null && input != null)
 				return provider.getDocument(input);

 		}
 		return null;
 	}

 	/**
 	 * Returns the selection on the editor or an invalid selection if none can be obtained. Returns
 	 * never <code>null</code>.
 	 *
 	 * @return the current selection, never <code>null</code>
 	 */
 	private ITextSelection getSelection() {
 		ISelectionProvider provider= getSelectionProvider();
 		if (provider != null) {

 			ISelection selection= provider.getSelection();
 			if (selection instanceof ITextSelection)
 				return (ITextSelection) selection;
 		}

 		// null object
 		return TextSelection.emptySelection();
 	}

 }
	/*******************************************************************************
	* Copyright (c) 2000, 2003 IBM Corporation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Common Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/cpl-v10.html
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	*******************************************************************************/
	package org.eclipse.jdt.internal.ui.actions;

	import java.util.ResourceBundle;

	import org.eclipse.core.runtime.IStatus;
	import org.eclipse.core.runtime.Status;

	import org.eclipse.swt.custom.BusyIndicator;
	import org.eclipse.swt.widgets.Display;

	import org.eclipse.jface.viewers.ISelection;
	import org.eclipse.jface.viewers.ISelectionProvider;

	import org.eclipse.jface.text.Assert;
	import org.eclipse.jface.text.BadLocationException;
	import org.eclipse.jface.text.DocumentCommand;
	import org.eclipse.jface.text.IDocument;
	import org.eclipse.jface.text.IRegion;
	import org.eclipse.jface.text.IRewriteTarget;
	import org.eclipse.jface.text.ITextSelection;
	import org.eclipse.jface.text.ITypedRegion;
	import org.eclipse.jface.text.Position;
	import org.eclipse.jface.text.TextSelection;
	import org.eclipse.jface.text.TextUtilities;
	import org.eclipse.jface.text.source.ISourceViewer;

	import org.eclipse.ui.IEditorInput;
	import org.eclipse.ui.texteditor.IDocumentProvider;
	import org.eclipse.ui.texteditor.ITextEditor;
	import org.eclipse.ui.texteditor.ITextEditorExtension3;
	import org.eclipse.ui.texteditor.TextEditorAction;

	import org.eclipse.jdt.core.JavaCore;

	import org.eclipse.jdt.ui.PreferenceConstants;

	import org.eclipse.jdt.internal.ui.JavaPlugin;
	import org.eclipse.jdt.internal.ui.javaeditor.JavaEditor;
	import org.eclipse.jdt.internal.ui.text.IJavaPartitions;
	import org.eclipse.jdt.internal.ui.text.JavaHeuristicScanner;
	import org.eclipse.jdt.internal.ui.text.JavaIndenter;
	import org.eclipse.jdt.internal.ui.text.javadoc.JavaDocAutoIndentStrategy;


	/**
	* Indents a line or range of lines in a Java document to its correct position. No complete
	* AST must be present, the indentation is computed using heuristics. The algorith used is fast for
	* single lines, but does not store any information and therefore not so efficient for large line
	* ranges.
	*
	* @see org.eclipse.jdt.internal.ui.text.JavaHeuristicScanner
	* @see org.eclipse.jdt.internal.ui.text.JavaIndenter
	* @since 3.0
	*/
	public class IndentAction extends TextEditorAction {

	/** The caret offset after an indent operation. */
	private int fCaretOffset;

	/**
	* Whether this is the action invoked by TAB. When <code>true</code>, indentation behaves
	* differently to accomodate normal TAB operation.
	*/
	private final boolean fIsTabAction;

	/**
	* Creates a new instance.
	*
	* @param bundle the resource bundle
	* @param prefix the prefix to use for keys in <code>bundle</code>
	* @param editor the text editor
	*/
	public IndentAction(ResourceBundle bundle, String prefix, ITextEditor editor, boolean isTabAction) {
	super(bundle, prefix, editor);
	fIsTabAction= isTabAction;
	}

	/*
	* @see org.eclipse.jface.action.Action#run()
	*/
	public void run() {
	// update has been called by the framework
	if (!isEnabled() \|\| !validateEditorInputState())
	return;

	ITextSelection selection= getSelection();
	final IDocument document= getDocument();

	if (document != null) {

	final int offset= selection.getOffset();
	final int length= selection.getLength();
	final Position end= new Position(offset + length);
	final int firstLine, nLines;
	fCaretOffset= -1;

	try {
	document.addPosition(end);
	firstLine= document.getLineOfOffset(offset);
	// check for marginal (zero-length) lines
	int minusOne= length == 0 ? 0 : 1;
	nLines= document.getLineOfOffset(offset + length - minusOne) - firstLine + 1;
	} catch (BadLocationException e) {
	// will only happen on concurrent modification
	JavaPlugin.log(new Status(IStatus.ERROR, JavaPlugin.getPluginId(), IStatus.OK, "", e)); //$NON-NLS-1$
	return;
	}

	Runnable runnable= new Runnable() {
	public void run() {
	IRewriteTarget target= (IRewriteTarget)getTextEditor().getAdapter(IRewriteTarget.class);
	if (target != null) {
	target.beginCompoundChange();
	target.setRedraw(false);
	}

	try {
	JavaHeuristicScanner scanner= new JavaHeuristicScanner(document);
	JavaIndenter indenter= new JavaIndenter(document, scanner);
	boolean hasChanged= false;
	for (int i= 0; i < nLines; i++) {
	hasChanged \|= indentLine(document, firstLine + i, offset, indenter, scanner);
	}

	// update caret position: move to new position when indenting just one line
	// keep selection when indenting multiple
	int newOffset, newLength;
	if (fIsTabAction) {
	newOffset= fCaretOffset;
	newLength= 0;
	} else if (nLines > 1) {
	newOffset= offset;
	newLength= end.getOffset() - offset;
	} else {
	newOffset= fCaretOffset;
	newLength= 0;
	}

	// always reset the selection if anything was replaced
	// but not when we had a singleline nontab invocation
	if (newOffset != -1 && (hasChanged \|\| newOffset != offset \|\| newLength != length))
	selectAndReveal(newOffset, newLength);

	document.removePosition(end);
	} catch (BadLocationException e) {
	// will only happen on concurrent modification
	JavaPlugin.log(new Status(IStatus.ERROR, JavaPlugin.getPluginId(), IStatus.OK, "ConcurrentModification in IndentAction", e)); //$NON-NLS-1$

	} finally {

	if (target != null) {
	target.endCompoundChange();
	target.setRedraw(true);
	}
	}
	}
	};

	if (nLines > 50) {
	Display display= getTextEditor().getEditorSite().getWorkbenchWindow().getShell().getDisplay();
	BusyIndicator.showWhile(display, runnable);
	} else
	runnable.run();

	}
	}

	/**
	* Selects the given range on the editor.
	*
	* @param newOffset the selection offset
	* @param newLength the selection range
	*/
	private void selectAndReveal(int newOffset, int newLength) {
	Assert.isTrue(newOffset >= 0);
	Assert.isTrue(newLength >= 0);
	ITextEditor editor= getTextEditor();
	if (editor instanceof JavaEditor) {
	ISourceViewer viewer= ((JavaEditor)editor).getViewer();
	if (viewer != null)
	viewer.setSelectedRange(newOffset, newLength);
	} else
	// this is too intrusive, but will never get called anyway
	getTextEditor().selectAndReveal(newOffset, newLength);

	}

	/**
	* Indents a single line using the java heuristic scanner. Javadoc and multiline comments are
	* indented as specified by the <code>JavaDocAutoIndentStrategy</code>.
	*
	* @param document the document
	* @param line the line to be indented
	* @param caret the caret position
	* @param indenter the java indenter
	* @param scanner the heuristic scanner
	* @return <code>true</code> if <code>document</code> was modified, <code>false</code> otherwise
	* @throws BadLocationException if the document got changed concurrently
	*/
	private boolean indentLine(IDocument document, int line, int caret, JavaIndenter indenter, JavaHeuristicScanner scanner) throws BadLocationException {
	IRegion currentLine= document.getLineInformation(line);
	int offset= currentLine.getOffset();

	String indent= null;
	if (offset < document.getLength()) {
	ITypedRegion partition= TextUtilities.getPartition(document, IJavaPartitions.JAVA_PARTITIONING, offset);
	String type= partition.getType();
	if (partition.getOffset() < offset
	&& type.equals(IJavaPartitions.JAVA_DOC)
	\|\| type.equals(IJavaPartitions.JAVA_MULTI_LINE_COMMENT)) {

	// TODO this is a hack
	// what I want to do
	// new JavaDocAutoIndentStrategy().indentLineAtOffset(document, offset);
	// return;

	int start= 0;
	if (line > 0) {

	IRegion previousLine= document.getLineInformation(line - 1);
	start= previousLine.getOffset() + previousLine.getLength();
	}

	DocumentCommand command= new DocumentCommand() {};
	command.text= "\n"; //$NON-NLS-1$
	command.offset= start;
	new JavaDocAutoIndentStrategy(IJavaPartitions.JAVA_PARTITIONING).customizeDocumentCommand(document, command);
	int i= command.text.indexOf('*');
	if (i != -1)
	indent= command.text.substring(1, i);
	else
	indent= command.text.substring(1);
	}
	}

	// standard java indentation
	if (indent == null) {
	StringBuffer computed= indenter.computeIndentation(offset);
	if (computed != null)
	indent= computed.toString();
	else
	indent= new String();
	}

	// change document:
	// get current white space
	int lineLength= currentLine.getLength();
	int end= scanner.findNonWhitespaceForwardInAnyPartition(offset, offset + lineLength);
	if (end == JavaHeuristicScanner.NOT_FOUND)
	end= offset + lineLength;
	int length= end - offset;
	String currentIndent= document.get(offset, length);

	// if we are right before the text start / line end, and already after the insertion point
	// then just insert a tab.
	if (fIsTabAction && caret == end && whiteSpaceLength(currentIndent) >= whiteSpaceLength(indent)) {
	String tab= getTabEquivalent();
	document.replace(caret, 0, tab);
	fCaretOffset= caret + tab.length();
	return true;
	}

	// set the caret offset so it can be used when setting the selection
	if (caret >= offset && caret <= end)
	fCaretOffset= offset + indent.length();
	else
	fCaretOffset= -1;

	// only change the document if it is a real change
	if (!indent.equals(currentIndent)) {
	document.replace(offset, length, indent);
	return true;
	} else
	return false;
	}

	/**
	* Returns the size in characters of a string. All characters count one, tabs count the editor's
	* preference for the tab display
	*
	* @param indent the string to be measured.
	* @return
	*/
	private int whiteSpaceLength(String indent) {
	if (indent == null)
	return 0;
	else {
	int size= 0;
	int l= indent.length();
	int tabSize= JavaPlugin.getDefault().getPreferenceStore().getInt(PreferenceConstants.EDITOR_TAB_WIDTH);

	for (int i= 0; i < l; i++)
	size += indent.charAt(i) == '\t' ? tabSize : 1;
	return size;
	}
	}

	/**
	* Returns a tab equivalent, either as a tab character or as spaces, depending on the editor and
	* formatter preferences.
	*
	* @return a string representing one tab in the editor, never <code>null</code>
	*/
	private String getTabEquivalent() {
	String tab;
	if (JavaPlugin.getDefault().getPreferenceStore().getBoolean(PreferenceConstants.EDITOR_SPACES_FOR_TABS)) {
	int size= JavaCore.getPlugin().getPluginPreferences().getInt(JavaCore.FORMATTER_TAB_SIZE);
	StringBuffer buf= new StringBuffer();
	for (int i= 0; i< size; i++)
	buf.append(' ');
	tab= buf.toString();
	} else
	tab= "\t"; //$NON-NLS-1$

	return tab;
	}

	/**
	* Returns the editor's selection provider.
	*
	* @return the editor's selection provider or <code>null</code>
	*/
	private ISelectionProvider getSelectionProvider() {
	ITextEditor editor= getTextEditor();
	if (editor != null) {
	return editor.getSelectionProvider();
	}
	return null;
	}

	/*
	* @see org.eclipse.ui.texteditor.IUpdate#update()
	*/
	public void update() {
	super.update();

	if (isEnabled())
	if (fIsTabAction)
	setEnabled(canModifyEditor() && isSmartMode() && isValidSelection());
	else
	setEnabled(canModifyEditor() && !getSelection().isEmpty());
	}

	/**
	* Returns if the current selection is valid, i.e. whether it is empty and the caret in the
	* whitespace at the start of a line, or covers multiple lines.
	*
	* @return <code>true</code> if the selection is valid for an indent operation
	*/
	private boolean isValidSelection() {
	ITextSelection selection= getSelection();
	if (selection.isEmpty())
	return false;

	int offset= selection.getOffset();
	int length= selection.getLength();

	IDocument document= getDocument();
	if (document == null)
	return false;

	try {
	IRegion firstLine= document.getLineInformationOfOffset(offset);
	int lineOffset= firstLine.getOffset();

	// either the selection has to be empty and the caret in the WS at the line start
	// or the selection has to extend over multiple lines
	if (length == 0)
	return document.get(lineOffset, offset - lineOffset).trim().length() == 0;
	else
	// return lineOffset + firstLine.getLength() < offset + length;
	return false; // only enable for empty selections for now

	} catch (BadLocationException e) {
	}

	return false;
	}

	/**
	* Returns the smart preference state.
	*
	* @return <code>true</code> if smart mode is on, <code>false</code> otherwise
	*/
	private boolean isSmartMode() {
	ITextEditor editor= getTextEditor();

	if (editor instanceof ITextEditorExtension3)
	return ((ITextEditorExtension3) editor).getInsertMode() == ITextEditorExtension3.SMART_INSERT;

	return false;
	}

	/**
	* Returns the document currently displayed in the editor, or <code>null</code> if none can be
	* obtained.
	*
	* @return the current document or <code>null</code>
	*/
	private IDocument getDocument() {

	ITextEditor editor= getTextEditor();
	if (editor != null) {

	IDocumentProvider provider= editor.getDocumentProvider();
	IEditorInput input= editor.getEditorInput();
	if (provider != null && input != null)
	return provider.getDocument(input);

	}
	return null;
	}

	/**
	* Returns the selection on the editor or an invalid selection if none can be obtained. Returns
	* never <code>null</code>.
	*
	* @return the current selection, never <code>null</code>
	*/
	private ITextSelection getSelection() {
	ISelectionProvider provider= getSelectionProvider();
	if (provider != null) {

	ISelection selection= provider.getSelection();
	if (selection instanceof ITextSelection)
	return (ITextSelection) selection;
	}

	// null object
	return TextSelection.emptySelection();
	}

	}