org.eclipse.jface.text/src/org/eclipse/jface/text/hyperlink/DefaultHyperlinkPresenter.java - platform/eclipse.platform.text - Git at Google

 /*******************************************************************************
  * Copyright (c) 2000, 2008 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.jface.text.hyperlink;

 import org.eclipse.swt.SWT;
 import org.eclipse.swt.custom.StyleRange;
 import org.eclipse.swt.custom.StyledText;
 import org.eclipse.swt.graphics.Color;
 import org.eclipse.swt.graphics.Cursor;
 import org.eclipse.swt.graphics.RGB;
 import org.eclipse.swt.widgets.Display;

 import org.eclipse.core.runtime.Assert;

 import org.eclipse.jface.preference.IPreferenceStore;
 import org.eclipse.jface.preference.PreferenceConverter;
 import org.eclipse.jface.util.IPropertyChangeListener;
 import org.eclipse.jface.util.PropertyChangeEvent;

 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.ITextInputListener;
 import org.eclipse.jface.text.ITextPresentationListener;
 import org.eclipse.jface.text.ITextViewer;
 import org.eclipse.jface.text.ITextViewerExtension2;
 import org.eclipse.jface.text.ITextViewerExtension4;
 import org.eclipse.jface.text.Position;
 import org.eclipse.jface.text.Region;
 import org.eclipse.jface.text.TextPresentation;


 /**
  * The default hyperlink presenter underlines the
  * link and colors the line and the text with
  * the given color.
  * <p>
  * It can only be used together with the {@link HyperlinkManager#FIRST}
  * or the {@link HyperlinkManager#LONGEST_REGION_FIRST} hyperlink strategy.
  * </p>
  *
  * @since 3.1
  */
 public class DefaultHyperlinkPresenter implements IHyperlinkPresenter, IHyperlinkPresenterExtension, ITextPresentationListener, ITextInputListener, IDocumentListener, IPropertyChangeListener {

 	/**
 	 * A named preference that holds the color used for hyperlinks.
 	 * <p>
 	 * Value is of type <code>String</code>. A RGB color value encoded as a string
 	 * using class <code>PreferenceConverter</code>
 	 * </p>
 	 *
 	 * @see org.eclipse.jface.resource.StringConverter
 	 * @see org.eclipse.jface.preference.PreferenceConverter
 	 */
 	public final static String HYPERLINK_COLOR= "hyperlinkColor"; //$NON-NLS-1$


 	/** The text viewer. */
 	private ITextViewer fTextViewer;
 	/** The hand cursor. */
 	private Cursor fCursor;
 	/** The link color. */
 	private Color fColor;
 	/** The link color specification. May be <code>null</code>. */
 	private RGB fRGB;
 	/** Tells whether to dispose the color on uninstall. */
 	private boolean fDisposeColor;
 	/** The currently active region. */
 	private IRegion fActiveRegion;
 	/** The currently active style range as position. */
 	private Position fRememberedPosition;
 	/** The optional preference store. May be <code>null</code>. */
 	private IPreferenceStore fPreferenceStore;


 	/**
 	 * Creates a new default hyperlink presenter which uses
 	 * {@link #HYPERLINK_COLOR} to read the color from the given preference store.
 	 *
 	 * @param store the preference store
 	 */
 	public DefaultHyperlinkPresenter(IPreferenceStore store) {
 		fPreferenceStore= store;
 		fDisposeColor= true;
 	}

 	/**
 	 * Creates a new default hyperlink presenter.
 	 *
 	 * @param color the hyperlink color, to be disposed by the caller
 	 */
 	public DefaultHyperlinkPresenter(Color color) {
 		fDisposeColor= false;
 		fColor= color;
 	}

 	/**
 	 * Creates a new default hyperlink presenter.
 	 *
 	 * @param color the hyperlink color, to be disposed by the caller
 	 */
 	public DefaultHyperlinkPresenter(RGB color) {
 		fRGB= color;
 		fDisposeColor= true;
 	}

 	/*
 	 * @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#canShowMultipleHyperlinks()
 	 */
 	public boolean canShowMultipleHyperlinks() {
 		return false;
 	}

 	/*
 	 * @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#activate(org.eclipse.jdt.internal.ui.javaeditor.IHyperlink[])
 	 */
 	public void showHyperlinks(IHyperlink[] hyperlinks) {
 		Assert.isLegal(hyperlinks != null && hyperlinks.length == 1);
 		highlightRegion(hyperlinks[0].getHyperlinkRegion());
 		activateCursor();
 	}

 	/*
 	 * @see org.eclipse.jface.text.hyperlink.IHyperlinkPresenterExtension#canHideHyperlinks()
 	 * @since 3.4
 	 */
 	public boolean canHideHyperlinks() {
 		return true;
 	}

 	/*
 	 * @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#deactivate()
 	 */
 	public void hideHyperlinks() {
 		repairRepresentation();
 		fRememberedPosition= null;
 	}

 	/*
 	 * @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#install(org.eclipse.jface.text.ITextViewer)
 	 */
 	public void install(ITextViewer textViewer) {
 		Assert.isNotNull(textViewer);
 		fTextViewer= textViewer;
 		fTextViewer.addTextInputListener(this);
 		if (fTextViewer instanceof ITextViewerExtension4)
 			((ITextViewerExtension4)fTextViewer).addTextPresentationListener(this);

 		StyledText text= fTextViewer.getTextWidget();
 		if (text != null && !text.isDisposed()) {
 			if (fPreferenceStore != null)
 				fColor= createColor(fPreferenceStore, HYPERLINK_COLOR, text.getDisplay());
 			else if (fRGB != null)
 				fColor= new Color(text.getDisplay(), fRGB);
 		}

 		if (fPreferenceStore != null)
 			fPreferenceStore.addPropertyChangeListener(this);
 	}

 	/*
 	 * @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#uninstall()
 	 */
 	public void uninstall() {
 		fTextViewer.removeTextInputListener(this);
 		IDocument document= fTextViewer.getDocument();
 		if (document != null)
 			document.removeDocumentListener(this);

 		if (fColor != null) {
 			if (fDisposeColor)
 				fColor.dispose();
 			fColor= null;
 		}

 		if (fCursor != null) {
 			fCursor.dispose();
 			fCursor= null;
 		}

 		if (fTextViewer instanceof ITextViewerExtension4)
 			((ITextViewerExtension4)fTextViewer).removeTextPresentationListener(this);
 		fTextViewer= null;

 		if (fPreferenceStore != null)
 			fPreferenceStore.removePropertyChangeListener(this);
 	}

 	public void setColor(Color color) {
 		Assert.isNotNull(fTextViewer);
 		fColor= color;
 	}

 	/*
 	 * @see org.eclipse.jface.text.ITextPresentationListener#applyTextPresentation(org.eclipse.jface.text.TextPresentation)
 	 */
 	public void applyTextPresentation(TextPresentation textPresentation) {
 		if (fActiveRegion == null)
 			return;
 		IRegion region= textPresentation.getExtent();
 		if (fActiveRegion.getOffset() + fActiveRegion.getLength() >= region.getOffset() && region.getOffset() + region.getLength() > fActiveRegion.getOffset()) {
 			StyleRange styleRange= new StyleRange(fActiveRegion.getOffset(), fActiveRegion.getLength(), fColor, null);
 			styleRange.underline= true;
 			textPresentation.mergeStyleRange(styleRange);
 		}
 	}

 	private void highlightRegion(IRegion region) {

 		if (region.equals(fActiveRegion))
 			return;

 		repairRepresentation();

 		StyledText text= fTextViewer.getTextWidget();
 		if (text == null || text.isDisposed())
 			return;

 		// Invalidate region ==> apply text presentation
 		fActiveRegion= region;
 		if (fTextViewer instanceof ITextViewerExtension2)
 			((ITextViewerExtension2)fTextViewer).invalidateTextPresentation(region.getOffset(), region.getLength());
 		else
 			fTextViewer.invalidateTextPresentation();
 	}

 	private void activateCursor() {
 		StyledText text= fTextViewer.getTextWidget();
 		if (text == null || text.isDisposed())
 			return;
 		Display display= text.getDisplay();
 		if (fCursor == null)
 			fCursor= new Cursor(display, SWT.CURSOR_HAND);
 		text.setCursor(fCursor);
 	}

 	private void resetCursor() {
 		StyledText text= fTextViewer.getTextWidget();
 		if (text != null && !text.isDisposed())
 			text.setCursor(null);

 		if (fCursor != null) {
 			fCursor.dispose();
 			fCursor= null;
 		}
 	}

 	private void repairRepresentation() {

 		if (fActiveRegion == null)
 			return;

 		int offset= fActiveRegion.getOffset();
 		int length= fActiveRegion.getLength();
 		fActiveRegion= null;

 		resetCursor();

 		// Invalidate ==> remove applied text presentation
 		if (fTextViewer instanceof ITextViewerExtension2)
 			((ITextViewerExtension2) fTextViewer).invalidateTextPresentation(offset, length);
 		else
 			fTextViewer.invalidateTextPresentation();

 	}

 	/*
 	 * @see org.eclipse.jface.text.IDocumentListener#documentAboutToBeChanged(org.eclipse.jface.text.DocumentEvent)
 	 */
 	public void documentAboutToBeChanged(DocumentEvent event) {
 		if (fActiveRegion != null) {
 			fRememberedPosition= new Position(fActiveRegion.getOffset(), fActiveRegion.getLength());
 			try {
 				event.getDocument().addPosition(fRememberedPosition);
 			} catch (BadLocationException x) {
 				fRememberedPosition= null;
 			}
 		}
 	}

 	/*
 	 * @see org.eclipse.jface.text.IDocumentListener#documentChanged(org.eclipse.jface.text.DocumentEvent)
 	 */
 	public void documentChanged(DocumentEvent event) {
 		if (fRememberedPosition != null) {
 			if (!fRememberedPosition.isDeleted()) {
 				event.getDocument().removePosition(fRememberedPosition);
 				fActiveRegion= new Region(fRememberedPosition.getOffset(), fRememberedPosition.getLength());
 			} else {
 				fActiveRegion= new Region(event.getOffset(), event.getLength());
 			}
 			fRememberedPosition= null;

 			StyledText widget= fTextViewer.getTextWidget();
 			if (widget != null && !widget.isDisposed()) {
 				widget.getDisplay().asyncExec(new Runnable() {
 					public void run() {
 						hideHyperlinks();
 					}
 				});
 			}
 		}
 	}

 	/*
 	 * @see org.eclipse.jface.text.ITextInputListener#inputDocumentAboutToBeChanged(org.eclipse.jface.text.IDocument, org.eclipse.jface.text.IDocument)
 	 */
 	public void inputDocumentAboutToBeChanged(IDocument oldInput, IDocument newInput) {
 		if (oldInput == null)
 			return;
 		hideHyperlinks();
 		oldInput.removeDocumentListener(this);
 	}

 	/*
 	 * @see org.eclipse.jface.text.ITextInputListener#inputDocumentChanged(org.eclipse.jface.text.IDocument, org.eclipse.jface.text.IDocument)
 	 */
 	public void inputDocumentChanged(IDocument oldInput, IDocument newInput) {
 		if (newInput == null)
 			return;
 		newInput.addDocumentListener(this);
 	}

 	/**
 	 * Creates a color from the information stored in the given preference store.
 	 *
 	 * @param store the preference store
 	 * @param key the key
 	 * @param display the display
 	 * @return the color or <code>null</code> if there is no such information available
 	 */
 	private Color createColor(IPreferenceStore store, String key, Display display) {

 		RGB rgb= null;

 		if (store.contains(key)) {

 			if (store.isDefault(key))
 				rgb= PreferenceConverter.getDefaultColor(store, key);
 			else
 				rgb= PreferenceConverter.getColor(store, key);

 			if (rgb != null)
 				return new Color(display, rgb);
 		}

 		return null;
 	}

 	/*
 	 * @see org.eclipse.jface.util.IPropertyChangeListener#propertyChange(org.eclipse.jface.util.PropertyChangeEvent)
 	 */
 	public void propertyChange(PropertyChangeEvent event) {
 		if (!HYPERLINK_COLOR.equals(event.getProperty()))
 			return;

 		if (fDisposeColor && fColor != null && !fColor.isDisposed())
 			fColor.dispose();
 		fColor= null;

 		StyledText textWidget= fTextViewer.getTextWidget();
 		if (textWidget != null && !textWidget.isDisposed())
 			fColor= createColor(fPreferenceStore, HYPERLINK_COLOR, textWidget.getDisplay());
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2000, 2008 IBM Corporation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	*******************************************************************************/
	package org.eclipse.jface.text.hyperlink;

	import org.eclipse.swt.SWT;
	import org.eclipse.swt.custom.StyleRange;
	import org.eclipse.swt.custom.StyledText;
	import org.eclipse.swt.graphics.Color;
	import org.eclipse.swt.graphics.Cursor;
	import org.eclipse.swt.graphics.RGB;
	import org.eclipse.swt.widgets.Display;

	import org.eclipse.core.runtime.Assert;

	import org.eclipse.jface.preference.IPreferenceStore;
	import org.eclipse.jface.preference.PreferenceConverter;
	import org.eclipse.jface.util.IPropertyChangeListener;
	import org.eclipse.jface.util.PropertyChangeEvent;

	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.ITextInputListener;
	import org.eclipse.jface.text.ITextPresentationListener;
	import org.eclipse.jface.text.ITextViewer;
	import org.eclipse.jface.text.ITextViewerExtension2;
	import org.eclipse.jface.text.ITextViewerExtension4;
	import org.eclipse.jface.text.Position;
	import org.eclipse.jface.text.Region;
	import org.eclipse.jface.text.TextPresentation;


	/**
	* The default hyperlink presenter underlines the
	* link and colors the line and the text with
	* the given color.
	* <p>
	* It can only be used together with the {@link HyperlinkManager#FIRST}
	* or the {@link HyperlinkManager#LONGEST_REGION_FIRST} hyperlink strategy.
	* </p>
	*
	* @since 3.1
	*/
	public class DefaultHyperlinkPresenter implements IHyperlinkPresenter, IHyperlinkPresenterExtension, ITextPresentationListener, ITextInputListener, IDocumentListener, IPropertyChangeListener {

	/**
	* A named preference that holds the color used for hyperlinks.
	* <p>
	* Value is of type <code>String</code>. A RGB color value encoded as a string
	* using class <code>PreferenceConverter</code>
	* </p>
	*
	* @see org.eclipse.jface.resource.StringConverter
	* @see org.eclipse.jface.preference.PreferenceConverter
	*/
	public final static String HYPERLINK_COLOR= "hyperlinkColor"; //$NON-NLS-1$


	/** The text viewer. */
	private ITextViewer fTextViewer;
	/** The hand cursor. */
	private Cursor fCursor;
	/** The link color. */
	private Color fColor;
	/** The link color specification. May be <code>null</code>. */
	private RGB fRGB;
	/** Tells whether to dispose the color on uninstall. */
	private boolean fDisposeColor;
	/** The currently active region. */
	private IRegion fActiveRegion;
	/** The currently active style range as position. */
	private Position fRememberedPosition;
	/** The optional preference store. May be <code>null</code>. */
	private IPreferenceStore fPreferenceStore;


	/**
	* Creates a new default hyperlink presenter which uses
	* {@link #HYPERLINK_COLOR} to read the color from the given preference store.
	*
	* @param store the preference store
	*/
	public DefaultHyperlinkPresenter(IPreferenceStore store) {
	fPreferenceStore= store;
	fDisposeColor= true;
	}

	/**
	* Creates a new default hyperlink presenter.
	*
	* @param color the hyperlink color, to be disposed by the caller
	*/
	public DefaultHyperlinkPresenter(Color color) {
	fDisposeColor= false;
	fColor= color;
	}

	/**
	* Creates a new default hyperlink presenter.
	*
	* @param color the hyperlink color, to be disposed by the caller
	*/
	public DefaultHyperlinkPresenter(RGB color) {
	fRGB= color;
	fDisposeColor= true;
	}

	/*
	* @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#canShowMultipleHyperlinks()
	*/
	public boolean canShowMultipleHyperlinks() {
	return false;
	}

	/*
	* @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#activate(org.eclipse.jdt.internal.ui.javaeditor.IHyperlink[])
	*/
	public void showHyperlinks(IHyperlink[] hyperlinks) {
	Assert.isLegal(hyperlinks != null && hyperlinks.length == 1);
	highlightRegion(hyperlinks[0].getHyperlinkRegion());
	activateCursor();
	}

	/*
	* @see org.eclipse.jface.text.hyperlink.IHyperlinkPresenterExtension#canHideHyperlinks()
	* @since 3.4
	*/
	public boolean canHideHyperlinks() {
	return true;
	}

	/*
	* @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#deactivate()
	*/
	public void hideHyperlinks() {
	repairRepresentation();
	fRememberedPosition= null;
	}

	/*
	* @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#install(org.eclipse.jface.text.ITextViewer)
	*/
	public void install(ITextViewer textViewer) {
	Assert.isNotNull(textViewer);
	fTextViewer= textViewer;
	fTextViewer.addTextInputListener(this);
	if (fTextViewer instanceof ITextViewerExtension4)
	((ITextViewerExtension4)fTextViewer).addTextPresentationListener(this);

	StyledText text= fTextViewer.getTextWidget();
	if (text != null && !text.isDisposed()) {
	if (fPreferenceStore != null)
	fColor= createColor(fPreferenceStore, HYPERLINK_COLOR, text.getDisplay());
	else if (fRGB != null)
	fColor= new Color(text.getDisplay(), fRGB);
	}

	if (fPreferenceStore != null)
	fPreferenceStore.addPropertyChangeListener(this);
	}

	/*
	* @see org.eclipse.jdt.internal.ui.javaeditor.IHyperlinkControl#uninstall()
	*/
	public void uninstall() {
	fTextViewer.removeTextInputListener(this);
	IDocument document= fTextViewer.getDocument();
	if (document != null)
	document.removeDocumentListener(this);

	if (fColor != null) {
	if (fDisposeColor)
	fColor.dispose();
	fColor= null;
	}

	if (fCursor != null) {
	fCursor.dispose();
	fCursor= null;
	}

	if (fTextViewer instanceof ITextViewerExtension4)
	((ITextViewerExtension4)fTextViewer).removeTextPresentationListener(this);
	fTextViewer= null;

	if (fPreferenceStore != null)
	fPreferenceStore.removePropertyChangeListener(this);
	}

	public void setColor(Color color) {
	Assert.isNotNull(fTextViewer);
	fColor= color;
	}

	/*
	* @see org.eclipse.jface.text.ITextPresentationListener#applyTextPresentation(org.eclipse.jface.text.TextPresentation)
	*/
	public void applyTextPresentation(TextPresentation textPresentation) {
	if (fActiveRegion == null)
	return;
	IRegion region= textPresentation.getExtent();
	if (fActiveRegion.getOffset() + fActiveRegion.getLength() >= region.getOffset() && region.getOffset() + region.getLength() > fActiveRegion.getOffset()) {
	StyleRange styleRange= new StyleRange(fActiveRegion.getOffset(), fActiveRegion.getLength(), fColor, null);
	styleRange.underline= true;
	textPresentation.mergeStyleRange(styleRange);
	}
	}

	private void highlightRegion(IRegion region) {

	if (region.equals(fActiveRegion))
	return;

	repairRepresentation();

	StyledText text= fTextViewer.getTextWidget();
	if (text == null \|\| text.isDisposed())
	return;

	// Invalidate region ==> apply text presentation
	fActiveRegion= region;
	if (fTextViewer instanceof ITextViewerExtension2)
	((ITextViewerExtension2)fTextViewer).invalidateTextPresentation(region.getOffset(), region.getLength());
	else
	fTextViewer.invalidateTextPresentation();
	}

	private void activateCursor() {
	StyledText text= fTextViewer.getTextWidget();
	if (text == null \|\| text.isDisposed())
	return;
	Display display= text.getDisplay();
	if (fCursor == null)
	fCursor= new Cursor(display, SWT.CURSOR_HAND);
	text.setCursor(fCursor);
	}

	private void resetCursor() {
	StyledText text= fTextViewer.getTextWidget();
	if (text != null && !text.isDisposed())
	text.setCursor(null);

	if (fCursor != null) {
	fCursor.dispose();
	fCursor= null;
	}
	}

	private void repairRepresentation() {

	if (fActiveRegion == null)
	return;

	int offset= fActiveRegion.getOffset();
	int length= fActiveRegion.getLength();
	fActiveRegion= null;

	resetCursor();

	// Invalidate ==> remove applied text presentation
	if (fTextViewer instanceof ITextViewerExtension2)
	((ITextViewerExtension2) fTextViewer).invalidateTextPresentation(offset, length);
	else
	fTextViewer.invalidateTextPresentation();

	}

	/*
	* @see org.eclipse.jface.text.IDocumentListener#documentAboutToBeChanged(org.eclipse.jface.text.DocumentEvent)
	*/
	public void documentAboutToBeChanged(DocumentEvent event) {
	if (fActiveRegion != null) {
	fRememberedPosition= new Position(fActiveRegion.getOffset(), fActiveRegion.getLength());
	try {
	event.getDocument().addPosition(fRememberedPosition);
	} catch (BadLocationException x) {
	fRememberedPosition= null;
	}
	}
	}

	/*
	* @see org.eclipse.jface.text.IDocumentListener#documentChanged(org.eclipse.jface.text.DocumentEvent)
	*/
	public void documentChanged(DocumentEvent event) {
	if (fRememberedPosition != null) {
	if (!fRememberedPosition.isDeleted()) {
	event.getDocument().removePosition(fRememberedPosition);
	fActiveRegion= new Region(fRememberedPosition.getOffset(), fRememberedPosition.getLength());
	} else {
	fActiveRegion= new Region(event.getOffset(), event.getLength());
	}
	fRememberedPosition= null;

	StyledText widget= fTextViewer.getTextWidget();
	if (widget != null && !widget.isDisposed()) {
	widget.getDisplay().asyncExec(new Runnable() {
	public void run() {
	hideHyperlinks();
	}
	});
	}
	}
	}

	/*
	* @see org.eclipse.jface.text.ITextInputListener#inputDocumentAboutToBeChanged(org.eclipse.jface.text.IDocument, org.eclipse.jface.text.IDocument)
	*/
	public void inputDocumentAboutToBeChanged(IDocument oldInput, IDocument newInput) {
	if (oldInput == null)
	return;
	hideHyperlinks();
	oldInput.removeDocumentListener(this);
	}

	/*
	* @see org.eclipse.jface.text.ITextInputListener#inputDocumentChanged(org.eclipse.jface.text.IDocument, org.eclipse.jface.text.IDocument)
	*/
	public void inputDocumentChanged(IDocument oldInput, IDocument newInput) {
	if (newInput == null)
	return;
	newInput.addDocumentListener(this);
	}

	/**
	* Creates a color from the information stored in the given preference store.
	*
	* @param store the preference store
	* @param key the key
	* @param display the display
	* @return the color or <code>null</code> if there is no such information available
	*/
	private Color createColor(IPreferenceStore store, String key, Display display) {

	RGB rgb= null;

	if (store.contains(key)) {

	if (store.isDefault(key))
	rgb= PreferenceConverter.getDefaultColor(store, key);
	else
	rgb= PreferenceConverter.getColor(store, key);

	if (rgb != null)
	return new Color(display, rgb);
	}

	return null;
	}

	/*
	* @see org.eclipse.jface.util.IPropertyChangeListener#propertyChange(org.eclipse.jface.util.PropertyChangeEvent)
	*/
	public void propertyChange(PropertyChangeEvent event) {
	if (!HYPERLINK_COLOR.equals(event.getProperty()))
	return;

	if (fDisposeColor && fColor != null && !fColor.isDisposed())
	fColor.dispose();
	fColor= null;

	StyledText textWidget= fTextViewer.getTextWidget();
	if (textWidget != null && !textWidget.isDisposed())
	fColor= createColor(fPreferenceStore, HYPERLINK_COLOR, textWidget.getDisplay());
	}
	}