org.eclipse.ui.editors/src/org/eclipse/ui/texteditor/ChainedPreferenceStore.java - platform/eclipse.platform.text - Git at Google

 /*******************************************************************************
  * Copyright (c) 2000, 2010 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.ui.texteditor;

 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;

 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.ListenerList;

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


 /**
  * Preference store that composes multiple preference stores in a
  * chain and serves a preference value from the first preference store in the
  * chain that contains the preference.
  * <p>
  * This preference store is read-only i.e. write access
  * throws an {@link java.lang.UnsupportedOperationException}.</p>
  *
  * @since 3.0
  */
 public class ChainedPreferenceStore implements IPreferenceStore {

 	/** Child preference stores. */
 	private IPreferenceStore[] fPreferenceStores;

 	/** Listeners on this chained preference store. */
 	private ListenerList fClientListeners= new ListenerList(ListenerList.IDENTITY);

 	/** Listeners on the child preference stores. */
 	private List<PropertyChangeListener> fChildListeners= new ArrayList<>();

 	/**
 	 * Listener on the chained preference stores. Forwards only the events
 	 * that are visible to clients.
 	 */
 	private class PropertyChangeListener implements IPropertyChangeListener {

 		/** Preference store to listen too. */
 		private IPreferenceStore fPreferenceStore;

 		/**
 		 * Initialize with the given preference store.
 		 *
 		 * @param preferenceStore the preference store
 		 */
 		public PropertyChangeListener(IPreferenceStore preferenceStore) {
 			setPreferenceStore(preferenceStore);
 		}

 		@Override
 		public void propertyChange(PropertyChangeEvent event) {
 			IPreferenceStore childPreferenceStore= getPreferenceStore();
 			handlePropertyChangeEvent(childPreferenceStore, event);
 		}

 		/**
 		 * Registers this listener on the preference store.
 		 */
 		public void register() {
 			getPreferenceStore().addPropertyChangeListener(this);
 		}

 		/**
 		 * Unregisters this listener from the preference store.
 		 */
 		public void unregister() {
 			getPreferenceStore().removePropertyChangeListener(this);
 		}

 		/**
 		 * Returns the preference store.
 		 *
 		 * @return the preference store
 		 */
 		public IPreferenceStore getPreferenceStore() {
 			return fPreferenceStore;
 		}

 		/**
 		 * Sets the preference store.
 		 *
 		 * @param preferenceStore the preference store to set
 		 */
 		public void setPreferenceStore(IPreferenceStore preferenceStore) {
 			fPreferenceStore= preferenceStore;
 		}

 	}

 	/**
 	 * Sets the chained preference stores.
 	 *
 	 * @param preferenceStores the chained preference stores to set
 	 */
 	public ChainedPreferenceStore(IPreferenceStore[] preferenceStores) {
 		Assert.isTrue(preferenceStores != null && preferenceStores.length > 0);
 		fPreferenceStores= new IPreferenceStore[preferenceStores.length];
 		System.arraycopy(preferenceStores, 0, fPreferenceStores, 0, preferenceStores.length);
 		// Create listeners
 		for (int i= 0, length= fPreferenceStores.length; i < length; i++) {
 			PropertyChangeListener listener= new PropertyChangeListener(fPreferenceStores[i]);
 			fChildListeners.add(listener);
 		}
 	}

 	@Override
 	public void addPropertyChangeListener(IPropertyChangeListener listener) {
 		if (fClientListeners.size() == 0) {
 			registerChildListeners();
 		}
 		fClientListeners.add(listener);
 	}

 	@Override
 	public void removePropertyChangeListener(IPropertyChangeListener listener) {
 		fClientListeners.remove(listener);
 		if (fClientListeners.size() == 0) {
 			unregisterChildListeners();
 		}
 	}

 	@Override
 	public boolean contains(String name) {
 		return getVisibleStore(name) != null;
 	}

 	@Override
 	public void firePropertyChangeEvent(String name, Object oldValue, Object newValue) {
 		firePropertyChangeEvent(new PropertyChangeEvent(this, name, oldValue, newValue));
 	}

 	/**
 	 * Fire the given property change event.
 	 *
 	 * @param event the property change event
 	 */
 	private void firePropertyChangeEvent(PropertyChangeEvent event) {
 		Object[] listeners= fClientListeners.getListeners();
 		for (int i= 0; i < listeners.length; i++)
 			 ((IPropertyChangeListener) listeners[i]).propertyChange(event);
 	}

 	@Override
 	public boolean getBoolean(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getBoolean(name);
 		return BOOLEAN_DEFAULT_DEFAULT;
 	}

 	@Override
 	public boolean getDefaultBoolean(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getDefaultBoolean(name);
 		return BOOLEAN_DEFAULT_DEFAULT;
 	}

 	@Override
 	public double getDefaultDouble(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getDefaultDouble(name);
 		return DOUBLE_DEFAULT_DEFAULT;
 	}

 	@Override
 	public float getDefaultFloat(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getDefaultFloat(name);
 		return FLOAT_DEFAULT_DEFAULT;
 	}

 	@Override
 	public int getDefaultInt(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getDefaultInt(name);
 		return INT_DEFAULT_DEFAULT;
 	}

 	@Override
 	public long getDefaultLong(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getDefaultLong(name);
 		return LONG_DEFAULT_DEFAULT;
 	}

 	@Override
 	public String getDefaultString(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getDefaultString(name);
 		return STRING_DEFAULT_DEFAULT;
 	}

 	@Override
 	public double getDouble(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getDouble(name);
 		return DOUBLE_DEFAULT_DEFAULT;
 	}

 	@Override
 	public float getFloat(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getFloat(name);
 		return FLOAT_DEFAULT_DEFAULT;
 	}

 	@Override
 	public int getInt(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getInt(name);
 		return INT_DEFAULT_DEFAULT;
 	}

 	@Override
 	public long getLong(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getLong(name);
 		return LONG_DEFAULT_DEFAULT;
 	}

 	@Override
 	public String getString(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.getString(name);
 		return STRING_DEFAULT_DEFAULT;
 	}

 	@Override
 	public boolean isDefault(String name) {
 		IPreferenceStore visibleStore= getVisibleStore(name);
 		if (visibleStore != null)
 			return visibleStore.isDefault(name);
 		return false;
 	}

 	@Override
 	public boolean needsSaving() {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void putValue(String name, String value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setDefault(String name, double value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setDefault(String name, float value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setDefault(String name, int value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setDefault(String name, long value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setDefault(String name, String defaultObject) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setDefault(String name, boolean value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setToDefault(String name) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setValue(String name, double value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setValue(String name, float value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setValue(String name, int value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setValue(String name, long value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setValue(String name, String value) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	public void setValue(String name, boolean value) {
 		throw new UnsupportedOperationException();
 	}

 	/**
 	 * Handle property change event from the child listener with the given child preference store.
 	 *
 	 * @param childPreferenceStore the child preference store
 	 * @param event the event
 	 */
 	private void handlePropertyChangeEvent(IPreferenceStore childPreferenceStore, PropertyChangeEvent event) {
 		String property= event.getProperty();
 		Object oldValue= event.getOldValue();
 		Object newValue= event.getNewValue();

 		IPreferenceStore visibleStore= getVisibleStore(property);

 		/*
 		 * Assume that the property is there but has no default value (its owner relies on the default-default value)
 		 * see https://bugs.eclipse.org/bugs/show_bug.cgi?id=52827
 		 */
 		if (visibleStore == null && newValue != null)
 			visibleStore= childPreferenceStore;

 		if (visibleStore == null) {
 			// no visible store
 			if (oldValue != null)
 				// removal in child, last in chain -> removal in this chained preference store
 				firePropertyChangeEvent(event);
 		} else if (visibleStore == childPreferenceStore) {
 			// event from visible store
 			if (oldValue != null) {
 				// change in child, visible store -> change in this chained preference store
 				firePropertyChangeEvent(event);
 			} else {
 				// insertion in child
 				IPreferenceStore oldVisibleStore= null;
 				int i= 0;
 				int length= fPreferenceStores.length;
 				while (i < length && fPreferenceStores[i++] != visibleStore) {
 					// do nothing
 				}
 				while (oldVisibleStore == null && i < length) {
 					if (fPreferenceStores[i].contains(property))
 						oldVisibleStore= fPreferenceStores[i];
 					i++;
 				}

 				if (oldVisibleStore == null) {
 					// insertion in child, first in chain -> insertion in this chained preference store
 					firePropertyChangeEvent(event);
 				} else {
 					// insertion in child, not first in chain
 					oldValue= getOtherValue(property, oldVisibleStore, newValue);
 					if (!oldValue.equals(newValue))
 						// insertion in child, different old value -> change in this chained preference store
 						firePropertyChangeEvent(property, oldValue, newValue);
 					// else: insertion in child, same old value -> no change in this chained preference store
 				}
 			}
 		} else {
 			// event from other than the visible store
 			boolean eventBeforeVisibleStore= false;
 			for (int i= 0, length= fPreferenceStores.length; i < length; i++) {
 				IPreferenceStore store= fPreferenceStores[i];
 				if (store == visibleStore)
 					break;
 				if (store == childPreferenceStore) {
 					eventBeforeVisibleStore= true;
 					break;
 				}
 			}

 			if (eventBeforeVisibleStore) {
 				// removal in child, before visible store

 				/*
 				 * The original event's new value can be non-null (removed assertion).
 				 * see https://bugs.eclipse.org/bugs/show_bug.cgi?id=69419
 				 */

 				newValue= getOtherValue(property, visibleStore, oldValue);
 				if (!newValue.equals(oldValue))
 					// removal in child, before visible store, different old value -> change in this chained preference store
 					firePropertyChangeEvent(property, oldValue, newValue);
 				// else: removal in child, before visible store, same old value -> no change in this chained preference store
 			}
 			// else: event behind visible store -> no change in this chained preference store
 		}
 	}

 	/**
 	 * Returns an object of the same dynamic type as <code>thisValue</code>, the returned object
 	 * encapsulates the value of the <code>property</code> from the preference <code>store</code>.
 	 *
 	 * @param property the name of the considered property
 	 * @param store the preference store
 	 * @param thisValue the given value
 	 * @return the other value
 	 */
 	private Object getOtherValue(String property, IPreferenceStore store, Object thisValue) {

 		if (thisValue instanceof Boolean)
 			return store.getBoolean(property) ? Boolean.TRUE : Boolean.FALSE;
 		else if (thisValue instanceof Double)
 			return new Double(store.getDouble(property));
 		else if (thisValue instanceof Float)
 			return new Float(store.getFloat(property));
 		else if (thisValue instanceof Integer)
 			return new Integer(store.getInt(property));
 		else if (thisValue instanceof Long)
 			return new Long(store.getLong(property));
 		else if (thisValue instanceof String)
 			return store.getString(property);

 		return store.getString(property);
 	}

 	/**
 	 * Returns the preference store from which the given property's value
 	 * is visible.
 	 *
 	 * @param property the name of the property
 	 * @return the preference store from which the property's value is visible,
 	 * 	<code>null</code> if the property is unknown
 	 */
 	private IPreferenceStore getVisibleStore(String property) {
 		IPreferenceStore visibleStore= null;

 		for (int i= 0, length= fPreferenceStores.length; i < length && visibleStore == null; i++) {
 			IPreferenceStore store= fPreferenceStores[i];
 			if (store.contains(property))
 				visibleStore= store;
 		}
 		return visibleStore;
 	}

 	/**
 	 * Register the child listeners on the child preference stores.
 	 */
 	private void registerChildListeners() {
 		Iterator<PropertyChangeListener> iter= fChildListeners.iterator();
 		while (iter.hasNext()) {
 			PropertyChangeListener listener= iter.next();
 			listener.register();
 		}
 	}

 	/**
 	 * Unregister the child listeners from the child preference stores.
 	 */
 	private void unregisterChildListeners() {
 		Iterator<PropertyChangeListener> iter= fChildListeners.iterator();
 		while (iter.hasNext()) {
 			PropertyChangeListener listener= iter.next();
 			listener.unregister();
 		}
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2000, 2010 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.ui.texteditor;

	import java.util.ArrayList;
	import java.util.Iterator;
	import java.util.List;

	import org.eclipse.core.runtime.Assert;
	import org.eclipse.core.runtime.ListenerList;

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


	/**
	* Preference store that composes multiple preference stores in a
	* chain and serves a preference value from the first preference store in the
	* chain that contains the preference.
	* <p>
	* This preference store is read-only i.e. write access
	* throws an {@link java.lang.UnsupportedOperationException}.</p>
	*
	* @since 3.0
	*/
	public class ChainedPreferenceStore implements IPreferenceStore {

	/** Child preference stores. */
	private IPreferenceStore[] fPreferenceStores;

	/** Listeners on this chained preference store. */
	private ListenerList fClientListeners= new ListenerList(ListenerList.IDENTITY);

	/** Listeners on the child preference stores. */
	private List<PropertyChangeListener> fChildListeners= new ArrayList<>();

	/**
	* Listener on the chained preference stores. Forwards only the events
	* that are visible to clients.
	*/
	private class PropertyChangeListener implements IPropertyChangeListener {

	/** Preference store to listen too. */
	private IPreferenceStore fPreferenceStore;

	/**
	* Initialize with the given preference store.
	*
	* @param preferenceStore the preference store
	*/
	public PropertyChangeListener(IPreferenceStore preferenceStore) {
	setPreferenceStore(preferenceStore);
	}

	@Override
	public void propertyChange(PropertyChangeEvent event) {
	IPreferenceStore childPreferenceStore= getPreferenceStore();
	handlePropertyChangeEvent(childPreferenceStore, event);
	}

	/**
	* Registers this listener on the preference store.
	*/
	public void register() {
	getPreferenceStore().addPropertyChangeListener(this);
	}

	/**
	* Unregisters this listener from the preference store.
	*/
	public void unregister() {
	getPreferenceStore().removePropertyChangeListener(this);
	}

	/**
	* Returns the preference store.
	*
	* @return the preference store
	*/
	public IPreferenceStore getPreferenceStore() {
	return fPreferenceStore;
	}

	/**
	* Sets the preference store.
	*
	* @param preferenceStore the preference store to set
	*/
	public void setPreferenceStore(IPreferenceStore preferenceStore) {
	fPreferenceStore= preferenceStore;
	}

	}

	/**
	* Sets the chained preference stores.
	*
	* @param preferenceStores the chained preference stores to set
	*/
	public ChainedPreferenceStore(IPreferenceStore[] preferenceStores) {
	Assert.isTrue(preferenceStores != null && preferenceStores.length > 0);
	fPreferenceStores= new IPreferenceStore[preferenceStores.length];
	System.arraycopy(preferenceStores, 0, fPreferenceStores, 0, preferenceStores.length);
	// Create listeners
	for (int i= 0, length= fPreferenceStores.length; i < length; i++) {
	PropertyChangeListener listener= new PropertyChangeListener(fPreferenceStores[i]);
	fChildListeners.add(listener);
	}
	}

	@Override
	public void addPropertyChangeListener(IPropertyChangeListener listener) {
	if (fClientListeners.size() == 0) {
	registerChildListeners();
	}
	fClientListeners.add(listener);
	}

	@Override
	public void removePropertyChangeListener(IPropertyChangeListener listener) {
	fClientListeners.remove(listener);
	if (fClientListeners.size() == 0) {
	unregisterChildListeners();
	}
	}

	@Override
	public boolean contains(String name) {
	return getVisibleStore(name) != null;
	}

	@Override
	public void firePropertyChangeEvent(String name, Object oldValue, Object newValue) {
	firePropertyChangeEvent(new PropertyChangeEvent(this, name, oldValue, newValue));
	}

	/**
	* Fire the given property change event.
	*
	* @param event the property change event
	*/
	private void firePropertyChangeEvent(PropertyChangeEvent event) {
	Object[] listeners= fClientListeners.getListeners();
	for (int i= 0; i < listeners.length; i++)
	((IPropertyChangeListener) listeners[i]).propertyChange(event);
	}

	@Override
	public boolean getBoolean(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getBoolean(name);
	return BOOLEAN_DEFAULT_DEFAULT;
	}

	@Override
	public boolean getDefaultBoolean(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getDefaultBoolean(name);
	return BOOLEAN_DEFAULT_DEFAULT;
	}

	@Override
	public double getDefaultDouble(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getDefaultDouble(name);
	return DOUBLE_DEFAULT_DEFAULT;
	}

	@Override
	public float getDefaultFloat(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getDefaultFloat(name);
	return FLOAT_DEFAULT_DEFAULT;
	}

	@Override
	public int getDefaultInt(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getDefaultInt(name);
	return INT_DEFAULT_DEFAULT;
	}

	@Override
	public long getDefaultLong(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getDefaultLong(name);
	return LONG_DEFAULT_DEFAULT;
	}

	@Override
	public String getDefaultString(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getDefaultString(name);
	return STRING_DEFAULT_DEFAULT;
	}

	@Override
	public double getDouble(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getDouble(name);
	return DOUBLE_DEFAULT_DEFAULT;
	}

	@Override
	public float getFloat(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getFloat(name);
	return FLOAT_DEFAULT_DEFAULT;
	}

	@Override
	public int getInt(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getInt(name);
	return INT_DEFAULT_DEFAULT;
	}

	@Override
	public long getLong(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getLong(name);
	return LONG_DEFAULT_DEFAULT;
	}

	@Override
	public String getString(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.getString(name);
	return STRING_DEFAULT_DEFAULT;
	}

	@Override
	public boolean isDefault(String name) {
	IPreferenceStore visibleStore= getVisibleStore(name);
	if (visibleStore != null)
	return visibleStore.isDefault(name);
	return false;
	}

	@Override
	public boolean needsSaving() {
	throw new UnsupportedOperationException();
	}

	@Override
	public void putValue(String name, String value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setDefault(String name, double value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setDefault(String name, float value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setDefault(String name, int value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setDefault(String name, long value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setDefault(String name, String defaultObject) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setDefault(String name, boolean value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setToDefault(String name) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setValue(String name, double value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setValue(String name, float value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setValue(String name, int value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setValue(String name, long value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setValue(String name, String value) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void setValue(String name, boolean value) {
	throw new UnsupportedOperationException();
	}

	/**
	* Handle property change event from the child listener with the given child preference store.
	*
	* @param childPreferenceStore the child preference store
	* @param event the event
	*/
	private void handlePropertyChangeEvent(IPreferenceStore childPreferenceStore, PropertyChangeEvent event) {
	String property= event.getProperty();
	Object oldValue= event.getOldValue();
	Object newValue= event.getNewValue();

	IPreferenceStore visibleStore= getVisibleStore(property);

	/*
	* Assume that the property is there but has no default value (its owner relies on the default-default value)
	* see https://bugs.eclipse.org/bugs/show_bug.cgi?id=52827
	*/
	if (visibleStore == null && newValue != null)
	visibleStore= childPreferenceStore;

	if (visibleStore == null) {
	// no visible store
	if (oldValue != null)
	// removal in child, last in chain -> removal in this chained preference store
	firePropertyChangeEvent(event);
	} else if (visibleStore == childPreferenceStore) {
	// event from visible store
	if (oldValue != null) {
	// change in child, visible store -> change in this chained preference store
	firePropertyChangeEvent(event);
	} else {
	// insertion in child
	IPreferenceStore oldVisibleStore= null;
	int i= 0;
	int length= fPreferenceStores.length;
	while (i < length && fPreferenceStores[i++] != visibleStore) {
	// do nothing
	}
	while (oldVisibleStore == null && i < length) {
	if (fPreferenceStores[i].contains(property))
	oldVisibleStore= fPreferenceStores[i];
	i++;
	}

	if (oldVisibleStore == null) {
	// insertion in child, first in chain -> insertion in this chained preference store
	firePropertyChangeEvent(event);
	} else {
	// insertion in child, not first in chain
	oldValue= getOtherValue(property, oldVisibleStore, newValue);
	if (!oldValue.equals(newValue))
	// insertion in child, different old value -> change in this chained preference store
	firePropertyChangeEvent(property, oldValue, newValue);
	// else: insertion in child, same old value -> no change in this chained preference store
	}
	}
	} else {
	// event from other than the visible store
	boolean eventBeforeVisibleStore= false;
	for (int i= 0, length= fPreferenceStores.length; i < length; i++) {
	IPreferenceStore store= fPreferenceStores[i];
	if (store == visibleStore)
	break;
	if (store == childPreferenceStore) {
	eventBeforeVisibleStore= true;
	break;
	}
	}

	if (eventBeforeVisibleStore) {
	// removal in child, before visible store

	/*
	* The original event's new value can be non-null (removed assertion).
	* see https://bugs.eclipse.org/bugs/show_bug.cgi?id=69419
	*/

	newValue= getOtherValue(property, visibleStore, oldValue);
	if (!newValue.equals(oldValue))
	// removal in child, before visible store, different old value -> change in this chained preference store
	firePropertyChangeEvent(property, oldValue, newValue);
	// else: removal in child, before visible store, same old value -> no change in this chained preference store
	}
	// else: event behind visible store -> no change in this chained preference store
	}
	}

	/**
	* Returns an object of the same dynamic type as <code>thisValue</code>, the returned object
	* encapsulates the value of the <code>property</code> from the preference <code>store</code>.
	*
	* @param property the name of the considered property
	* @param store the preference store
	* @param thisValue the given value
	* @return the other value
	*/
	private Object getOtherValue(String property, IPreferenceStore store, Object thisValue) {

	if (thisValue instanceof Boolean)
	return store.getBoolean(property) ? Boolean.TRUE : Boolean.FALSE;
	else if (thisValue instanceof Double)
	return new Double(store.getDouble(property));
	else if (thisValue instanceof Float)
	return new Float(store.getFloat(property));
	else if (thisValue instanceof Integer)
	return new Integer(store.getInt(property));
	else if (thisValue instanceof Long)
	return new Long(store.getLong(property));
	else if (thisValue instanceof String)
	return store.getString(property);

	return store.getString(property);
	}

	/**
	* Returns the preference store from which the given property's value
	* is visible.
	*
	* @param property the name of the property
	* @return the preference store from which the property's value is visible,
	* <code>null</code> if the property is unknown
	*/
	private IPreferenceStore getVisibleStore(String property) {
	IPreferenceStore visibleStore= null;

	for (int i= 0, length= fPreferenceStores.length; i < length && visibleStore == null; i++) {
	IPreferenceStore store= fPreferenceStores[i];
	if (store.contains(property))
	visibleStore= store;
	}
	return visibleStore;
	}

	/**
	* Register the child listeners on the child preference stores.
	*/
	private void registerChildListeners() {
	Iterator<PropertyChangeListener> iter= fChildListeners.iterator();
	while (iter.hasNext()) {
	PropertyChangeListener listener= iter.next();
	listener.register();
	}
	}

	/**
	* Unregister the child listeners from the child preference stores.
	*/
	private void unregisterChildListeners() {
	Iterator<PropertyChangeListener> iter= fChildListeners.iterator();
	while (iter.hasNext()) {
	PropertyChangeListener listener= iter.next();
	listener.unregister();
	}
	}
	}