org.eclipse.ui.workbench.texteditor/src/org/eclipse/ui/texteditor/MoveLinesAction.java - platform/eclipse.platform.text - 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.ui.texteditor;

 import java.util.ResourceBundle;

 import org.eclipse.swt.custom.StyledText;
 import org.eclipse.swt.custom.VerifyKeyListener;
 import org.eclipse.swt.events.FocusEvent;
 import org.eclipse.swt.events.FocusListener;
 import org.eclipse.swt.events.MouseEvent;
 import org.eclipse.swt.events.MouseListener;
 import org.eclipse.swt.events.VerifyEvent;
 import org.eclipse.swt.graphics.Point;
 import org.eclipse.swt.widgets.Event;

 import org.eclipse.jface.text.Assert;
 import org.eclipse.jface.text.BadLocationException;
 import org.eclipse.jface.text.DocumentEvent;
 import org.eclipse.jface.text.IDocument;
 import org.eclipse.jface.text.IDocumentListener;
 import org.eclipse.jface.text.IRegion;
 import org.eclipse.jface.text.IRewriteTarget;
 import org.eclipse.jface.text.ITextSelection;
 import org.eclipse.jface.text.ITextViewer;
 import org.eclipse.jface.text.ITextViewerExtension5;
 import org.eclipse.jface.text.TextSelection;
 import org.eclipse.jface.text.source.ISourceViewer;

 /**
  * Action for moving selected lines in an editor.
  * @since 3.0
  */
 public class MoveLinesAction extends TextEditorAction {

 	/**
 	 * Detects the end of a compound edit command. The user is assumed to have ended the command
 	 * when
 	 * <ul>
 	 * <li>entering any text with a different key combination than the one used to move / copy</li>
 	 * <li>clicking anywhere in the editor</li>
 	 * <li>the viewer loses focus</li>
 	 * <li>the underlying document gets changed due to anything but this action</li>
 	 * </ul>
 	 */
 	private class ExitStrategy implements VerifyKeyListener, MouseListener, FocusListener, IDocumentListener {

 		/**
 		 * The widget this instance is registered with for <code>VerifyKey</code>-, <code>Mouse</code>-
 		 * and <code>FocusEvent</code>s, or <code>null</code> if not registered.
 		 */
 		private StyledText fWidgetEventSource;
 		/**
 		 * The document this instance is registered with for <code>DocumentEvent</code>s,
 		 * or <code>null</code> if not registered.
 		 */
 		private IDocument fDocumentEventSource;
 		/**
 		 * Indicates whether there are any pending registrations.<br/>
 		 * Invariant: <code>fIsInstalled || (fWidgetEventSource == fDocumentEventSource == null)</code>
 		 */
 		private boolean fIsInstalled;

 		/**
 		 * Installs the exit strategy with all event sources.
 		 */
 		public void install() {
 			if (fIsInstalled)
 				uninstall();
 			fIsInstalled= true;

 			ISourceViewer viewer= fEditor.getSourceViewer();
 			if (viewer == null)
 				return;

 			fWidgetEventSource= viewer.getTextWidget();
 			if (fWidgetEventSource == null)
 				return;

 			fWidgetEventSource.addVerifyKeyListener(this);
 			fWidgetEventSource.addMouseListener(this);
 			fWidgetEventSource.addFocusListener(this);

 			fDocumentEventSource= viewer.getDocument();
 			if (fDocumentEventSource != null)
 				fDocumentEventSource.addDocumentListener(this);
 		}

 		/**
 		 * Uninstalls the exit strategy with all event sources it was previously registered with.
 		 */
 		public void uninstall() {
 			if (fWidgetEventSource != null) {
 				fWidgetEventSource.removeVerifyKeyListener(this);
 				fWidgetEventSource.removeMouseListener(this);
 				fWidgetEventSource.removeFocusListener(this);
 				fWidgetEventSource= null;
 			}
 			if (fDocumentEventSource != null) {
 				fDocumentEventSource.removeDocumentListener(this);
 				fDocumentEventSource= null;
 			}
 			fIsInstalled= false;
 		}

 		public void verifyKey(VerifyEvent event) {
 			if (event.stateMask != fStateMask) {
 				endCompoundEdit();
 			}
 		}

 		public void mouseDoubleClick(MouseEvent e) {
 			endCompoundEdit();
 		}

 		public void mouseDown(MouseEvent e) {
 			endCompoundEdit();
 		}

 		public void mouseUp(MouseEvent e) {}

 		public void focusLost(FocusEvent e) {
 			endCompoundEdit();
 		}

 		public void focusGained(FocusEvent e) {}

 		public void documentAboutToBeChanged(DocumentEvent event) {
 			// don't do this since it will break interaction between the moveUp and moveDown actions.
 //			if (!fDescription.correspondsTo(event)) endCompoundEdit();
 		}

 		public void documentChanged(DocumentEvent event) {}
 	}

 	/* keys */

 	/** Key for status message upon illegal move. <p>Value {@value}</p> */
 	private static final String ILLEGAL_MOVE= "Editor.MoveLines.IllegalMove.status"; //$NON-NLS-1$

 	/* state variables - define what this action does */

 	/** <code>true</code> if lines are shifted upwards, <code>false</code> otherwise. */
 	private final boolean fUpwards;
 	/** <code>true</code> if lines are to be copied instead of moved. */
 	private final boolean fCopy;
 	/** The editor we are working on. */
 	private final  AbstractTextEditor fEditor;

 	/* compound members of this action */

 	/** The exit strategy that will detect the ending of a compound edit */
 	private final ExitStrategy fExitStrategy= new ExitStrategy();

 	/* process variables - may change in every run() */

 	/**
 	 * Set to <code>true</code> by <code>getMovingSelection</code> if the resulting selection
 	 * should include the last delimiter.
 	 */
 	private boolean fAddDelimiter;
 	/** <code>true</code> if a compound move / copy is going on. */
 	private boolean fEditInProgress= false;
 	/** stateMask for this action - if it changes, the edition is considered to be ended */
 	private int fStateMask;
 //	/** Description of the last edition triggered by this action */
 //	private EditDescription fDescription= new EditDescription();

 	/**
 	 * Creates and initializes the action for the given text editor.
 	 * The action configures its visual representation from the given resource
 	 * bundle.
 	 *
 	 * @param bundle the resource bundle
 	 * @param prefix a prefix to be prepended to the various resource keys
 	 *   (described in <code>ResourceAction</code> constructor), or  <code>null</code> if none
 	 * @param editor the text editor
 	 * @param upwards <code>true</code>if the selected lines should be moved upwards,
 	 * <code>false</code> if downwards
 	 * @param copy if <code>true</code>, the action will copy lines instead of moving them
 	 * @see TextEditorAction#TextEditorAction(ResourceBundle, String, ITextEditor)
 	 */
 	public MoveLinesAction(ResourceBundle bundle, String prefix, AbstractTextEditor editor, boolean upwards, boolean copy) {
 		super(bundle, prefix, editor);
 		fEditor= editor;
 		fUpwards= upwards;
 		fCopy= copy;
 		update();
 	}

 	/**
 	 * Ends the compound change.
 	 */
 	private void beginCompoundEdit() {
 		if (fEditInProgress || fEditor == null)
 			return;

 		fEditInProgress= true;

 		fExitStrategy.install();

 		IRewriteTarget target= (IRewriteTarget)fEditor.getAdapter(IRewriteTarget.class);
 		if (target != null) {
 			target.beginCompoundChange();
 		}
 	}

 	/**
 	 * Checks if <code>selection</code> is contained by the visible region of <code>viewer</code>.
 	 * As a special case, a selection is considered contained even if it extends over the visible
 	 * region, but the extension stays on a partially contained line and contains only white space.
 	 *
 	 * @param selection the selection to be checked
 	 * @param viewer the viewer displaying a visible region of <code>selection</code>'s document.
 	 * @return <code>true</code>, if <code>selection</code> is contained, <code>false</code> otherwise.
 	 */
 	private boolean containedByVisibleRegion(ITextSelection selection, ISourceViewer viewer) {
 		int min= selection.getOffset();
 		int max= min + selection.getLength();
 		IDocument document= viewer.getDocument();

 		IRegion visible;
 		if (viewer instanceof ITextViewerExtension5)
 			visible= ((ITextViewerExtension5) viewer).getModelCoverage();
 		else
 			visible= viewer.getVisibleRegion();

 		int visOffset= visible.getOffset();
 		try {
 			if (visOffset > min) {
 				if (document.getLineOfOffset(visOffset) != selection.getStartLine())
 					return false;
 				if (!isWhitespace(document.get(min, visOffset - min))) {
 					showStatus();
 					return false;
 				}
 			}
 			int visEnd= visOffset + visible.getLength();
 			if (visEnd < max) {
 				if (document.getLineOfOffset(visEnd) != selection.getEndLine())
 					return false;
 				if (!isWhitespace(document.get(visEnd, max - visEnd))) {
 					showStatus();
 					return false;
 				}
 			}
 			return true;
 		} catch (BadLocationException e) {
 		}
 		return false;
 	}

 	/**
 	 * Ends the compound change.
 	 */
 	private void endCompoundEdit() {
 		if (!fEditInProgress || fEditor == null)
 			return;

 		fExitStrategy.uninstall();

 		IRewriteTarget target= (IRewriteTarget)fEditor.getAdapter(IRewriteTarget.class);
 		if (target != null) {
 			target.endCompoundChange();
 		}

 		fEditInProgress= false;
 	}

 	/**
 	 * Given a selection on a document, computes the lines fully or partially covered by
 	 * <code>selection</code>. A line in the document is considered covered if
 	 * <code>selection</code> comprises any characters on it, including the terminating delimiter.
 	 * <p>Note that the last line in a selection is not considered covered if the selection only
 	 * comprises the line delimiter at its beginning (that is considered part of the second last
 	 * line).
 	 * As a special case, if the selection is empty, a line is considered covered if the caret is
 	 * at any position in the line, including between the delimiter and the start of the line. The
 	 * line containing the delimiter is not considered covered in that case.
 	 * </p>
 	 *
 	 * @param document the document <code>selection</code> refers to
 	 * @param selection a selection on <code>document</code>
 	 * @param viewer the <code>ISourceViewer</code> displaying <code>document</code>
 	 * @return a selection describing the range of lines (partially) covered by
 	 * <code>selection</code>, without any terminating line delimiters
 	 * @throws BadLocationException if the selection is out of bounds (when the underlying document has changed during the call)
 	 */
 	private ITextSelection getMovingSelection(IDocument document, ITextSelection selection, ISourceViewer viewer) throws BadLocationException {
 		int low= document.getLineOffset(selection.getStartLine());
 		int endLine= selection.getEndLine();
 		int high= document.getLineOffset(endLine) + document.getLineLength(endLine);

 		// get everything up to last line without its delimiter
 		String delim= document.getLineDelimiter(endLine);
 		if (delim != null)
 			high -= delim.length();

 		// the new selection will cover the entire lines being moved, except for the last line's
 		// delimiter. The exception to this rule is an empty last line, which will stay covered
 		// including its delimiter
 		if (delim != null && document.getLineLength(endLine) == delim.length())
 			fAddDelimiter= true;
 		else
 			fAddDelimiter= false;

 		return new TextSelection(document, low, high - low);
 	}

 	/**
 	 * Computes the region of the skipped line given the text block to be moved. If
 	 * <code>fUpwards</code> is <code>true</code>, the line above <code>selection</code>
 	 * is selected, otherwise the line below.
 	 *
 	 * @param document the document <code>selection</code> refers to
 	 * @param selection the selection on <code>document</code> that will be moved.
 	 * @return the region comprising the line that <code>selection</code> will be moved over, without its terminating delimiter.
 	 */
 	private ITextSelection getSkippedLine(IDocument document, ITextSelection selection) {
 		int skippedLineN= (fUpwards ? selection.getStartLine() - 1 : selection.getEndLine() + 1);
 		if (skippedLineN < 0 || skippedLineN >= document.getNumberOfLines())
 			return null;
 		try {
 			IRegion line= document.getLineInformation(skippedLineN);
 			return new TextSelection(document, line.getOffset(), line.getLength());
 		} catch (BadLocationException e) {
 			// only happens on concurrent modifications
 			return null;
 		}
 	}

 	/**
 	 * Checks for white space in a string.
 	 *
 	 * @param string the string to be checked or <code>null</code>
 	 * @return <code>true</code> if <code>string</code> contains only white space or is
 	 * <code>null</code>, <code>false</code> otherwise
 	 */
 	private boolean isWhitespace(String string) {
 		return string == null ? true : string.trim().length() == 0;
 	}

 	/*
 	 * @see org.eclipse.jface.action.IAction#run()
 	 */
 	public void runWithEvent(Event event) {

 		updateShortCut(event);

 		// get involved objects
 		if (fEditor == null)
 			return;

 		if (!validateEditorInputState())
 			return;

 		ISourceViewer viewer= fEditor.getSourceViewer();
 		if (viewer == null)
 			return;

 		IDocument document= viewer.getDocument();
 		if (document == null)
 			return;

 		StyledText widget= viewer.getTextWidget();
 		if (widget == null)
 			return;

 		// get selection
 		Point p= viewer.getSelectedRange();
 		if (p == null)
 			return;

 		ITextSelection sel= new TextSelection(document, p.x, p.y);

 		ITextSelection skippedLine= getSkippedLine(document, sel);
 		if (skippedLine == null)
 			return;

 		try {

 			ITextSelection movingArea= getMovingSelection(document, sel, viewer);

 			// if either the skipped line or the moving lines are outside the widget's
 			// visible area, bail out
 			if (!containedByVisibleRegion(movingArea, viewer) || !containedByVisibleRegion(skippedLine, viewer))
 				return;

 			// get the content to be moved around: the moving (selected) area and the skipped line
 			String moving= movingArea.getText();
 			String skipped= skippedLine.getText();
 			if (moving == null || skipped == null)
 				return;

 			String delim;
 			String insertion;
 			int offset, deviation;
 			if (fUpwards) {
 				delim= document.getLineDelimiter(skippedLine.getEndLine());
 				Assert.isNotNull(delim);
 				if (fCopy) {
 					insertion= moving + delim;
 					offset= movingArea.getOffset();
 					deviation= 0;
 				} else {
 					insertion= moving + delim + skipped;
 					offset= skippedLine.getOffset();
 					deviation= -skippedLine.getLength() - delim.length();
 				}
 			} else {
 				delim= document.getLineDelimiter(movingArea.getEndLine());
 				Assert.isNotNull(delim);
 				if (fCopy) {
 					insertion= moving + delim;
 					offset= skippedLine.getOffset();
 					deviation= movingArea.getLength() + delim.length();
 				} else {
 					insertion= skipped + delim + moving;
 					offset= movingArea.getOffset();
 					deviation= skipped.length() + delim.length();
 				}
 			}

 			// modify the document
 			beginCompoundEdit();
 			if (fCopy) {
 //				fDescription= new EditDescription(offset, 0, insertion.length());
 				document.replace(offset, 0, insertion);
 			} else {
 //				fDescription= new EditDescription(offset, insertion.length(), insertion.length());
 				document.replace(offset, insertion.length(), insertion);
 			}

 			// move the selection along
 			int selOffset= movingArea.getOffset() + deviation;
 			int selLength= movingArea.getLength() + (fAddDelimiter ? delim.length() : 0);
 			if (! (viewer instanceof ITextViewerExtension5))
 				selLength= Math.min(selLength, viewer.getVisibleRegion().getOffset() + viewer.getVisibleRegion().getLength() - selOffset);
 			else {
 				// TODO need to check what is necessary in the projection case
 			}
 			selectAndReveal(viewer, selOffset, selLength);
 		} catch (BadLocationException x) {
 			// won't happen without concurrent modification - bail out
 			return;
 		}
 	}

 	/**
 	 * Saves the state mask of <code>event</code> for comparison with the next event in order to
 	 * detect key changes in the set of keys pressed by the user.
 	 *
 	 * @param event the event that triggered this action
 	 */
 	private void updateShortCut(Event event) {
 		fStateMask= event.stateMask;
 	}

 	/**
 	 * Performs similar to AbstractTextEditor.selectAndReveal, but does not update
 	 * the viewers highlight area.
 	 *
 	 * @param viewer the viewer that we want to select on
 	 * @param offset the offset of the selection
 	 * @param length the length of the selection
 	 */
 	private void selectAndReveal(ITextViewer viewer, int offset, int length) {
 		// invert selection to avoid jumping to the end of the selection in st.showSelection()
 		viewer.setSelectedRange(offset + length, -length);
 		//viewer.revealRange(offset, length); // will trigger jumping
 		StyledText st= viewer.getTextWidget();
 		if (st != null)
 			st.showSelection(); // only minimal scrolling
 	}

 	/**
 	 * Displays information in the status line why a line move is not possible
 	 */
 	private void showStatus() {
 		IEditorStatusLine status= (IEditorStatusLine) fEditor.getAdapter(IEditorStatusLine.class);
 		if (status == null)
 			return;
 		status.setMessage(false, EditorMessages.getString(ILLEGAL_MOVE), null);
 	}

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

 		if (isEnabled())
 			setEnabled(canModifyEditor());

 	}
 }
	/*******************************************************************************
	* 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.ui.texteditor;

	import java.util.ResourceBundle;

	import org.eclipse.swt.custom.StyledText;
	import org.eclipse.swt.custom.VerifyKeyListener;
	import org.eclipse.swt.events.FocusEvent;
	import org.eclipse.swt.events.FocusListener;
	import org.eclipse.swt.events.MouseEvent;
	import org.eclipse.swt.events.MouseListener;
	import org.eclipse.swt.events.VerifyEvent;
	import org.eclipse.swt.graphics.Point;
	import org.eclipse.swt.widgets.Event;

	import org.eclipse.jface.text.Assert;
	import org.eclipse.jface.text.BadLocationException;
	import org.eclipse.jface.text.DocumentEvent;
	import org.eclipse.jface.text.IDocument;
	import org.eclipse.jface.text.IDocumentListener;
	import org.eclipse.jface.text.IRegion;
	import org.eclipse.jface.text.IRewriteTarget;
	import org.eclipse.jface.text.ITextSelection;
	import org.eclipse.jface.text.ITextViewer;
	import org.eclipse.jface.text.ITextViewerExtension5;
	import org.eclipse.jface.text.TextSelection;
	import org.eclipse.jface.text.source.ISourceViewer;

	/**
	* Action for moving selected lines in an editor.
	* @since 3.0
	*/
	public class MoveLinesAction extends TextEditorAction {

	/**
	* Detects the end of a compound edit command. The user is assumed to have ended the command
	* when
	* <ul>
	* <li>entering any text with a different key combination than the one used to move / copy</li>
	* <li>clicking anywhere in the editor</li>
	* <li>the viewer loses focus</li>
	* <li>the underlying document gets changed due to anything but this action</li>
	* </ul>
	*/
	private class ExitStrategy implements VerifyKeyListener, MouseListener, FocusListener, IDocumentListener {

	/**
	* The widget this instance is registered with for <code>VerifyKey</code>-, <code>Mouse</code>-
	* and <code>FocusEvent</code>s, or <code>null</code> if not registered.
	*/
	private StyledText fWidgetEventSource;
	/**
	* The document this instance is registered with for <code>DocumentEvent</code>s,
	* or <code>null</code> if not registered.
	*/
	private IDocument fDocumentEventSource;
	/**
	* Indicates whether there are any pending registrations.<br/>
	* Invariant: <code>fIsInstalled \|\| (fWidgetEventSource == fDocumentEventSource == null)</code>
	*/
	private boolean fIsInstalled;

	/**
	* Installs the exit strategy with all event sources.
	*/
	public void install() {
	if (fIsInstalled)
	uninstall();
	fIsInstalled= true;

	ISourceViewer viewer= fEditor.getSourceViewer();
	if (viewer == null)
	return;

	fWidgetEventSource= viewer.getTextWidget();
	if (fWidgetEventSource == null)
	return;

	fWidgetEventSource.addVerifyKeyListener(this);
	fWidgetEventSource.addMouseListener(this);
	fWidgetEventSource.addFocusListener(this);

	fDocumentEventSource= viewer.getDocument();
	if (fDocumentEventSource != null)
	fDocumentEventSource.addDocumentListener(this);
	}

	/**
	* Uninstalls the exit strategy with all event sources it was previously registered with.
	*/
	public void uninstall() {
	if (fWidgetEventSource != null) {
	fWidgetEventSource.removeVerifyKeyListener(this);
	fWidgetEventSource.removeMouseListener(this);
	fWidgetEventSource.removeFocusListener(this);
	fWidgetEventSource= null;
	}
	if (fDocumentEventSource != null) {
	fDocumentEventSource.removeDocumentListener(this);
	fDocumentEventSource= null;
	}
	fIsInstalled= false;
	}

	public void verifyKey(VerifyEvent event) {
	if (event.stateMask != fStateMask) {
	endCompoundEdit();
	}
	}

	public void mouseDoubleClick(MouseEvent e) {
	endCompoundEdit();
	}

	public void mouseDown(MouseEvent e) {
	endCompoundEdit();
	}

	public void mouseUp(MouseEvent e) {}

	public void focusLost(FocusEvent e) {
	endCompoundEdit();
	}

	public void focusGained(FocusEvent e) {}

	public void documentAboutToBeChanged(DocumentEvent event) {
	// don't do this since it will break interaction between the moveUp and moveDown actions.
	// if (!fDescription.correspondsTo(event)) endCompoundEdit();
	}

	public void documentChanged(DocumentEvent event) {}
	}

	/* keys */

	/** Key for status message upon illegal move. <p>Value {@value}</p> */
	private static final String ILLEGAL_MOVE= "Editor.MoveLines.IllegalMove.status"; //$NON-NLS-1$

	/* state variables - define what this action does */

	/** <code>true</code> if lines are shifted upwards, <code>false</code> otherwise. */
	private final boolean fUpwards;
	/** <code>true</code> if lines are to be copied instead of moved. */
	private final boolean fCopy;
	/** The editor we are working on. */
	private final AbstractTextEditor fEditor;

	/* compound members of this action */

	/** The exit strategy that will detect the ending of a compound edit */
	private final ExitStrategy fExitStrategy= new ExitStrategy();

	/* process variables - may change in every run() */

	/**
	* Set to <code>true</code> by <code>getMovingSelection</code> if the resulting selection
	* should include the last delimiter.
	*/
	private boolean fAddDelimiter;
	/** <code>true</code> if a compound move / copy is going on. */
	private boolean fEditInProgress= false;
	/** stateMask for this action - if it changes, the edition is considered to be ended */
	private int fStateMask;
	// /** Description of the last edition triggered by this action */
	// private EditDescription fDescription= new EditDescription();

	/**
	* Creates and initializes the action for the given text editor.
	* The action configures its visual representation from the given resource
	* bundle.
	*
	* @param bundle the resource bundle
	* @param prefix a prefix to be prepended to the various resource keys
	* (described in <code>ResourceAction</code> constructor), or <code>null</code> if none
	* @param editor the text editor
	* @param upwards <code>true</code>if the selected lines should be moved upwards,
	* <code>false</code> if downwards
	* @param copy if <code>true</code>, the action will copy lines instead of moving them
	* @see TextEditorAction#TextEditorAction(ResourceBundle, String, ITextEditor)
	*/
	public MoveLinesAction(ResourceBundle bundle, String prefix, AbstractTextEditor editor, boolean upwards, boolean copy) {
	super(bundle, prefix, editor);
	fEditor= editor;
	fUpwards= upwards;
	fCopy= copy;
	update();
	}

	/**
	* Ends the compound change.
	*/
	private void beginCompoundEdit() {
	if (fEditInProgress \|\| fEditor == null)
	return;

	fEditInProgress= true;

	fExitStrategy.install();

	IRewriteTarget target= (IRewriteTarget)fEditor.getAdapter(IRewriteTarget.class);
	if (target != null) {
	target.beginCompoundChange();
	}
	}

	/**
	* Checks if <code>selection</code> is contained by the visible region of <code>viewer</code>.
	* As a special case, a selection is considered contained even if it extends over the visible
	* region, but the extension stays on a partially contained line and contains only white space.
	*
	* @param selection the selection to be checked
	* @param viewer the viewer displaying a visible region of <code>selection</code>'s document.
	* @return <code>true</code>, if <code>selection</code> is contained, <code>false</code> otherwise.
	*/
	private boolean containedByVisibleRegion(ITextSelection selection, ISourceViewer viewer) {
	int min= selection.getOffset();
	int max= min + selection.getLength();
	IDocument document= viewer.getDocument();

	IRegion visible;
	if (viewer instanceof ITextViewerExtension5)
	visible= ((ITextViewerExtension5) viewer).getModelCoverage();
	else
	visible= viewer.getVisibleRegion();

	int visOffset= visible.getOffset();
	try {
	if (visOffset > min) {
	if (document.getLineOfOffset(visOffset) != selection.getStartLine())
	return false;
	if (!isWhitespace(document.get(min, visOffset - min))) {
	showStatus();
	return false;
	}
	}
	int visEnd= visOffset + visible.getLength();
	if (visEnd < max) {
	if (document.getLineOfOffset(visEnd) != selection.getEndLine())
	return false;
	if (!isWhitespace(document.get(visEnd, max - visEnd))) {
	showStatus();
	return false;
	}
	}
	return true;
	} catch (BadLocationException e) {
	}
	return false;
	}

	/**
	* Ends the compound change.
	*/
	private void endCompoundEdit() {
	if (!fEditInProgress \|\| fEditor == null)
	return;

	fExitStrategy.uninstall();

	IRewriteTarget target= (IRewriteTarget)fEditor.getAdapter(IRewriteTarget.class);
	if (target != null) {
	target.endCompoundChange();
	}

	fEditInProgress= false;
	}

	/**
	* Given a selection on a document, computes the lines fully or partially covered by
	* <code>selection</code>. A line in the document is considered covered if
	* <code>selection</code> comprises any characters on it, including the terminating delimiter.
	* <p>Note that the last line in a selection is not considered covered if the selection only
	* comprises the line delimiter at its beginning (that is considered part of the second last
	* line).
	* As a special case, if the selection is empty, a line is considered covered if the caret is
	* at any position in the line, including between the delimiter and the start of the line. The
	* line containing the delimiter is not considered covered in that case.
	* </p>
	*
	* @param document the document <code>selection</code> refers to
	* @param selection a selection on <code>document</code>
	* @param viewer the <code>ISourceViewer</code> displaying <code>document</code>
	* @return a selection describing the range of lines (partially) covered by
	* <code>selection</code>, without any terminating line delimiters
	* @throws BadLocationException if the selection is out of bounds (when the underlying document has changed during the call)
	*/
	private ITextSelection getMovingSelection(IDocument document, ITextSelection selection, ISourceViewer viewer) throws BadLocationException {
	int low= document.getLineOffset(selection.getStartLine());
	int endLine= selection.getEndLine();
	int high= document.getLineOffset(endLine) + document.getLineLength(endLine);

	// get everything up to last line without its delimiter
	String delim= document.getLineDelimiter(endLine);
	if (delim != null)
	high -= delim.length();

	// the new selection will cover the entire lines being moved, except for the last line's
	// delimiter. The exception to this rule is an empty last line, which will stay covered
	// including its delimiter
	if (delim != null && document.getLineLength(endLine) == delim.length())
	fAddDelimiter= true;
	else
	fAddDelimiter= false;

	return new TextSelection(document, low, high - low);
	}

	/**
	* Computes the region of the skipped line given the text block to be moved. If
	* <code>fUpwards</code> is <code>true</code>, the line above <code>selection</code>
	* is selected, otherwise the line below.
	*
	* @param document the document <code>selection</code> refers to
	* @param selection the selection on <code>document</code> that will be moved.
	* @return the region comprising the line that <code>selection</code> will be moved over, without its terminating delimiter.
	*/
	private ITextSelection getSkippedLine(IDocument document, ITextSelection selection) {
	int skippedLineN= (fUpwards ? selection.getStartLine() - 1 : selection.getEndLine() + 1);
	if (skippedLineN < 0 \|\| skippedLineN >= document.getNumberOfLines())
	return null;
	try {
	IRegion line= document.getLineInformation(skippedLineN);
	return new TextSelection(document, line.getOffset(), line.getLength());
	} catch (BadLocationException e) {
	// only happens on concurrent modifications
	return null;
	}
	}

	/**
	* Checks for white space in a string.
	*
	* @param string the string to be checked or <code>null</code>
	* @return <code>true</code> if <code>string</code> contains only white space or is
	* <code>null</code>, <code>false</code> otherwise
	*/
	private boolean isWhitespace(String string) {
	return string == null ? true : string.trim().length() == 0;
	}

	/*
	* @see org.eclipse.jface.action.IAction#run()
	*/
	public void runWithEvent(Event event) {

	updateShortCut(event);

	// get involved objects
	if (fEditor == null)
	return;

	if (!validateEditorInputState())
	return;

	ISourceViewer viewer= fEditor.getSourceViewer();
	if (viewer == null)
	return;

	IDocument document= viewer.getDocument();
	if (document == null)
	return;

	StyledText widget= viewer.getTextWidget();
	if (widget == null)
	return;

	// get selection
	Point p= viewer.getSelectedRange();
	if (p == null)
	return;

	ITextSelection sel= new TextSelection(document, p.x, p.y);

	ITextSelection skippedLine= getSkippedLine(document, sel);
	if (skippedLine == null)
	return;

	try {

	ITextSelection movingArea= getMovingSelection(document, sel, viewer);

	// if either the skipped line or the moving lines are outside the widget's
	// visible area, bail out
	if (!containedByVisibleRegion(movingArea, viewer) \|\| !containedByVisibleRegion(skippedLine, viewer))
	return;

	// get the content to be moved around: the moving (selected) area and the skipped line
	String moving= movingArea.getText();
	String skipped= skippedLine.getText();
	if (moving == null \|\| skipped == null)
	return;

	String delim;
	String insertion;
	int offset, deviation;
	if (fUpwards) {
	delim= document.getLineDelimiter(skippedLine.getEndLine());
	Assert.isNotNull(delim);
	if (fCopy) {
	insertion= moving + delim;
	offset= movingArea.getOffset();
	deviation= 0;
	} else {
	insertion= moving + delim + skipped;
	offset= skippedLine.getOffset();
	deviation= -skippedLine.getLength() - delim.length();
	}
	} else {
	delim= document.getLineDelimiter(movingArea.getEndLine());
	Assert.isNotNull(delim);
	if (fCopy) {
	insertion= moving + delim;
	offset= skippedLine.getOffset();
	deviation= movingArea.getLength() + delim.length();
	} else {
	insertion= skipped + delim + moving;
	offset= movingArea.getOffset();
	deviation= skipped.length() + delim.length();
	}
	}

	// modify the document
	beginCompoundEdit();
	if (fCopy) {
	// fDescription= new EditDescription(offset, 0, insertion.length());
	document.replace(offset, 0, insertion);
	} else {
	// fDescription= new EditDescription(offset, insertion.length(), insertion.length());
	document.replace(offset, insertion.length(), insertion);
	}

	// move the selection along
	int selOffset= movingArea.getOffset() + deviation;
	int selLength= movingArea.getLength() + (fAddDelimiter ? delim.length() : 0);
	if (! (viewer instanceof ITextViewerExtension5))
	selLength= Math.min(selLength, viewer.getVisibleRegion().getOffset() + viewer.getVisibleRegion().getLength() - selOffset);
	else {
	// TODO need to check what is necessary in the projection case
	}
	selectAndReveal(viewer, selOffset, selLength);
	} catch (BadLocationException x) {
	// won't happen without concurrent modification - bail out
	return;
	}
	}

	/**
	* Saves the state mask of <code>event</code> for comparison with the next event in order to
	* detect key changes in the set of keys pressed by the user.
	*
	* @param event the event that triggered this action
	*/
	private void updateShortCut(Event event) {
	fStateMask= event.stateMask;
	}

	/**
	* Performs similar to AbstractTextEditor.selectAndReveal, but does not update
	* the viewers highlight area.
	*
	* @param viewer the viewer that we want to select on
	* @param offset the offset of the selection
	* @param length the length of the selection
	*/
	private void selectAndReveal(ITextViewer viewer, int offset, int length) {
	// invert selection to avoid jumping to the end of the selection in st.showSelection()
	viewer.setSelectedRange(offset + length, -length);
	//viewer.revealRange(offset, length); // will trigger jumping
	StyledText st= viewer.getTextWidget();
	if (st != null)
	st.showSelection(); // only minimal scrolling
	}

	/**
	* Displays information in the status line why a line move is not possible
	*/
	private void showStatus() {
	IEditorStatusLine status= (IEditorStatusLine) fEditor.getAdapter(IEditorStatusLine.class);
	if (status == null)
	return;
	status.setMessage(false, EditorMessages.getString(ILLEGAL_MOVE), null);
	}

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

	if (isEnabled())
	setEnabled(canModifyEditor());

	}
	}