[429636] Create preference page for groups

Create preference page to rank groups in order define which one will be
used by default.

Bug: 429636
Change-Id: If763cf54cef1f9f26c2714aca97b66e185f77270
Signed-off-by: Arthur Daussy <arthur.daussy@obeo.fr>

9 files changed, 984 insertions, 177 deletions

diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/emfcomparercpuimessages.properties b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/emfcomparercpuimessages.properties
index 7669af241..ebce98807 100644
--- a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/emfcomparercpuimessages.properties
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/emfcomparercpuimessages.properties
@@ -39,8 +39,15 @@ InteractiveUIContent.DESCRIPTION_COMPOSITE_LABEL = Description
 InteractiveUIContent.INCORRECT_SELECTION_TITLE = Incorrect selection
 InteractiveUIContent.INCORRECT_SELECTION_MESSAGE = At least one item has to be selected.
 
+GroupsInteractiveContent.AUTOMATIC_BEHAVIOR_GROUP_LABEL = Automatic behavior
+GroupsInteractiveContent.AUTOMATIC_BEHAVIOR_LABEL = Synchronize current group selection:
+
+
 PostProcessorPreferencePage.PREFERENCE_PAGE_DESCRIPTION = Select active post processors:
 
+GroupsPreferencePage.VIEWER_DESCRIPTION_LABEL = Rank each group by priority (Highest ranked enabled element will be use as default):
+GroupsPreferencePage.TWO_WAY_COMPARISON_TAB_LABEL = 2 way comparison
+GroupsPreferencePage.THREE_WAY_COMPARISON_TAB_LABEL = 3 way comparison
 EditorPreferencePage.mainTab.label = Main
 EditorPreferencePage.mainTab.colorHyperLink.label = See <a>''Color and Fonts''</a> preferences for EMF Compare colors.
 
diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/EnginesPreferencePage.java b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/EnginesPreferencePage.java
index 1021746b9..4ae568128 100644
--- a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/EnginesPreferencePage.java
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/EnginesPreferencePage.java
@@ -40,7 +40,8 @@ import org.eclipse.emf.compare.rcp.ui.EMFCompareRCPUIPlugin;
 import org.eclipse.emf.compare.rcp.ui.internal.EMFCompareRCPUIMessages;
 import org.eclipse.emf.compare.rcp.ui.internal.configuration.ui.AbstractConfigurationUI;
 import org.eclipse.emf.compare.rcp.ui.internal.configuration.ui.IConfigurationUIFactory;
-import org.eclipse.emf.compare.rcp.ui.internal.preferences.InteractiveUIContent.InteractiveUIBuilder;
+import org.eclipse.emf.compare.rcp.ui.internal.preferences.impl.InteractiveUIContent;
+import org.eclipse.emf.compare.rcp.ui.internal.preferences.impl.InteractiveUIContent.InteractiveUIBuilder;
 import org.eclipse.emf.compare.req.IReqEngine;
 import org.eclipse.jface.preference.PreferencePage;
 import org.eclipse.jface.resource.ImageDescriptor;
@@ -137,7 +138,7 @@ public class EnginesPreferencePage extends PreferencePage implements IWorkbenchP
 	 * @param tabComposite
 	 *            Holding composite.
 	 * @param dataHolder
-	 *            Data that will be synchronoze with the UI.
+	 *            Data that will be synchronized with the UI.
 	 * @param <T>
 	 *            type of engine.
 	 * @return {@link InteractiveUIContent} for a specific type of engine.
diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/GroupsPreferencePage.java b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/GroupsPreferencePage.java
new file mode 100644
index 000000000..f6e7e9b73
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/GroupsPreferencePage.java
@@ -0,0 +1,198 @@
+/*******************************************************************************
+ * Copyright (c) 2014 Obeo.
+ * 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:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.rcp.ui.internal.preferences;
+
+import java.util.List;
+
+import org.eclipse.core.runtime.preferences.InstanceScope;
+import org.eclipse.emf.compare.rcp.internal.extension.IItemDescriptor;
+import org.eclipse.emf.compare.rcp.ui.EMFCompareRCPUIPlugin;
+import org.eclipse.emf.compare.rcp.ui.internal.EMFCompareRCPUIMessages;
+import org.eclipse.emf.compare.rcp.ui.internal.preferences.impl.GroupsInteractiveContent;
+import org.eclipse.emf.compare.rcp.ui.internal.preferences.impl.ItemDescriptorLabelProvider;
+import org.eclipse.emf.compare.rcp.ui.internal.structuremergeviewer.groups.impl.DifferenceGroupManager;
+import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider;
+import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider.Descriptor;
+import org.eclipse.jface.preference.PreferencePage;
+import org.eclipse.jface.viewers.ArrayContentProvider;
+import org.eclipse.jface.viewers.ListViewer;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.layout.GridData;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Control;
+import org.eclipse.swt.widgets.Label;
+import org.eclipse.swt.widgets.TabFolder;
+import org.eclipse.swt.widgets.TabItem;
+import org.eclipse.ui.IWorkbench;
+import org.eclipse.ui.IWorkbenchPreferencePage;
+import org.eclipse.ui.preferences.ScopedPreferenceStore;
+
+/**
+ * Preference page for group providers.
+ * 
+ * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
+ */
+public class GroupsPreferencePage extends PreferencePage implements IWorkbenchPreferencePage {
+
+	/** UI content for two way comparison tab. */
+	private GroupsInteractiveContent twoWayComparisonContent;
+
+	/** UI content for three way comparison tab. */
+	private GroupsInteractiveContent threeWayComparisonContent;
+
+	/** {@link DifferenceGroupManager}. */
+	private DifferenceGroupManager groupManager = new DifferenceGroupManager(EMFCompareRCPUIPlugin
+			.getDefault().getEMFCompareUIPreferences(), EMFCompareRCPUIPlugin.getDefault()
+			.getItemDifferenceGroupProviderRegistry());
+
+	/**
+	 * {@inheritDoc}
+	 */
+	public void init(IWorkbench workbench) {
+		// Do not use InstanceScope.Instance to be compatible with Helios.
+		@SuppressWarnings("deprecation")
+		ScopedPreferenceStore store = new ScopedPreferenceStore(new InstanceScope(),
+				EMFCompareRCPUIPlugin.PLUGIN_ID);
+		setPreferenceStore(store);
+
+	}
+
+	@Override
+	protected Control createContents(Composite parent) {
+		parent.setLayout(new GridLayout(1, true));
+		Composite container = new Composite(parent, SWT.NONE);
+		container.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
+		container.setLayout(new GridLayout(1, true));
+
+		TabFolder tabFolder = new TabFolder(container, SWT.NONE);
+		tabFolder.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
+
+		fillTwoWayComparisonTab(tabFolder);
+		fillThreeWayComparisonTab(tabFolder);
+		return container;
+	}
+
+	/**
+	 * Fills the tab for two way comparison.
+	 * 
+	 * @param tabFolder
+	 *            Holding tab folder.
+	 */
+	private void fillTwoWayComparisonTab(TabFolder tabFolder) {
+		Composite tabSkeletonComposite = createTabSkeleton(tabFolder, EMFCompareRCPUIMessages
+				.getString("GroupsPreferencePage.TWO_WAY_COMPARISON_TAB_LABEL"), //$NON-NLS-1$
+				EMFCompareRCPUIMessages.getString("GroupsPreferencePage.VIEWER_DESCRIPTION_LABEL")); //$NON-NLS-1$
+
+		List<IItemDescriptor<Descriptor>> currentGroupRanking = groupManager.getCurrentGroupRanking(false);
+
+		twoWayComparisonContent = createInteractiveContent(tabSkeletonComposite, currentGroupRanking,
+				currentGroupRanking.get(0));
+	}
+
+	/**
+	 * Fills the tab for three way comparison.
+	 * 
+	 * @param tabFolder
+	 *            Holding tab folder.
+	 */
+	private void fillThreeWayComparisonTab(TabFolder tabFolder) {
+		Composite tabSkeletonComposite = createTabSkeleton(tabFolder, EMFCompareRCPUIMessages
+				.getString("GroupsPreferencePage.THREE_WAY_COMPARISON_TAB_LABEL"), //$NON-NLS-1$
+				EMFCompareRCPUIMessages.getString("GroupsPreferencePage.VIEWER_DESCRIPTION_LABEL")); //$NON-NLS-1$
+
+		List<IItemDescriptor<Descriptor>> currentGroupRanking = groupManager.getCurrentGroupRanking(true);
+		threeWayComparisonContent = createInteractiveContent(tabSkeletonComposite, currentGroupRanking,
+				currentGroupRanking.get(0));
+	}
+
+	/**
+	 * Creates an interactive content.
+	 * <p>
+	 * Interactive content aims at handling all ui that is modified with user interaction.
+	 * </p>
+	 * 
+	 * @param parent
+	 *            Parent Composite.
+	 * @param input
+	 *            Input of the viewer.
+	 * @param defaultSelection
+	 *            Default element that need to be selected.
+	 * @return A {@link GroupsInteractiveContent}
+	 */
+	private GroupsInteractiveContent createInteractiveContent(Composite parent,
+			List<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> input,
+			IItemDescriptor<IDifferenceGroupProvider.Descriptor> defaultSelection) {
+
+		final GroupsInteractiveContent interactiveUI = new GroupsInteractiveContent(parent);
+		createViewer(interactiveUI);
+		interactiveUI.setViewerInput(input);
+		interactiveUI.select(defaultSelection);
+
+		return interactiveUI;
+	}
+
+	/**
+	 * Creates skeleton of a tab.
+	 * 
+	 * @param tabFolder
+	 *            Holding tab folder.
+	 * @param tabLabel
+	 *            Label of the tab.
+	 * @param introText
+	 *            Text use as description a tab
+	 * @return Main composite of the tab
+	 */
+	private Composite createTabSkeleton(TabFolder tabFolder, String tabLabel, String introText) {
+		TabItem tbtmMain = new TabItem(tabFolder, SWT.NONE);
+		tbtmMain.setText(tabLabel);
+		Composite tabComposite = new Composite(tabFolder, SWT.NONE);
+		tbtmMain.setControl(tabComposite);
+		tabComposite.setLayout(new GridLayout(1, true));
+		GridData layoutData = new GridData(SWT.FILL, SWT.FILL, true, true, 1, 1);
+		tabComposite.setLayoutData(layoutData);
+		// Description text
+		Label introductionText = new Label(tabComposite, SWT.WRAP);
+		introductionText.setText(introText);
+		return tabComposite;
+	}
+
+	/**
+	 * Creates the list viewer holding items.
+	 * 
+	 * @param interactiveUI
+	 *            {@link GroupsInteractiveContent} in which the viewer need to be set up.
+	 */
+	private void createViewer(final GroupsInteractiveContent interactiveUI) {
+		int style = SWT.BORDER | SWT.V_SCROLL | SWT.FULL_SELECTION | SWT.SINGLE;
+		ListViewer descriptorViewer = new ListViewer(interactiveUI.getViewerComposite(), style);
+		interactiveUI.setViewer(descriptorViewer);
+		descriptorViewer.setContentProvider(ArrayContentProvider.getInstance());
+		descriptorViewer.setLabelProvider(new ItemDescriptorLabelProvider());
+		GridData gd = new GridData(SWT.FILL, SWT.FILL, true, true, 1, 1);
+		descriptorViewer.getControl().setLayoutData(gd);
+	}
+
+	@Override
+	public boolean performOk() {
+		groupManager.setCurrentGroupRanking(twoWayComparisonContent.getItems(), false);
+		groupManager.setCurrentGroupRanking(threeWayComparisonContent.getItems(), true);
+		return super.performOk();
+	}
+
+	@Override
+	protected void performDefaults() {
+		twoWayComparisonContent.setViewerInput(groupManager.getDefaultRankingConfiguration(false));
+		threeWayComparisonContent.setViewerInput(groupManager.getDefaultRankingConfiguration(true));
+		super.performDefaults();
+	}
+
+}
diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/PostProcessorPreferencePage.java b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/PostProcessorPreferencePage.java
index 878a81848..00a0efc56 100644
--- a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/PostProcessorPreferencePage.java
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/PostProcessorPreferencePage.java
@@ -29,7 +29,8 @@ import org.eclipse.emf.compare.rcp.internal.extension.impl.ItemUtil;
 import org.eclipse.emf.compare.rcp.internal.preferences.EMFComparePreferences;
 import org.eclipse.emf.compare.rcp.internal.tracer.TracingConstant;
 import org.eclipse.emf.compare.rcp.ui.internal.EMFCompareRCPUIMessages;
-import org.eclipse.emf.compare.rcp.ui.internal.preferences.InteractiveUIContent.InteractiveUIBuilder;
+import org.eclipse.emf.compare.rcp.ui.internal.preferences.impl.InteractiveUIContent;
+import org.eclipse.emf.compare.rcp.ui.internal.preferences.impl.InteractiveUIContent.InteractiveUIBuilder;
 import org.eclipse.jface.preference.PreferencePage;
 import org.eclipse.jface.resource.ImageDescriptor;
 import org.eclipse.swt.SWT;
@@ -51,21 +52,41 @@ public class PostProcessorPreferencePage extends PreferencePage implements IWork
 	/** Data holder. */
 	private DataHolder<IPostProcessor.Descriptor> dataHolder = new DataHolder<IPostProcessor.Descriptor>();
 
-	/** {@link InteractiveUIContent} */
-	private InteractiveUIContent interactiveUI = null;
+	/** {@link InteractiveUIContent}. */
+	private InteractiveUIContent interactiveUI;
 
+	/**
+	 * Constructor.
+	 */
 	public PostProcessorPreferencePage() {
 		super();
 	}
 
+	/**
+	 * Constructor.
+	 * 
+	 * @param title
+	 *            .
+	 * @param image
+	 *            .
+	 */
 	public PostProcessorPreferencePage(String title, ImageDescriptor image) {
 		super(title, image);
 	}
 
+	/**
+	 * Constructor.
+	 * 
+	 * @param title
+	 *            .
+	 */
 	public PostProcessorPreferencePage(String title) {
 		super(title);
 	}
 
+	/**
+	 * {@inheritDoc}
+	 */
 	public void init(IWorkbench workbench) {
 		// Do not use InstanceScope.Instance to be compatible with Helios.
 		@SuppressWarnings("deprecation")
@@ -110,10 +131,10 @@ public class PostProcessorPreferencePage extends PreferencePage implements IWork
 		if (TracingConstant.CONFIGURATION_TRACING_ACTIVATED) {
 			StringBuilder traceMessage = new StringBuilder("Post processor preference serialization:\n"); //$NON-NLS-1$
 			String prefDelimiter = " :\n"; //$NON-NLS-1$
-			String new_line = "\n"; //$NON-NLS-1$
+			String newLine = "\n"; //$NON-NLS-1$
 			traceMessage.append(EMFComparePreferences.DISABLED_POST_PROCESSOR).append(prefDelimiter).append(
 					getPreferenceStore().getString(EMFComparePreferences.DISABLED_POST_PROCESSOR)).append(
-					new_line);
+					newLine);
 			EMFCompareRCPPlugin.getDefault().log(IStatus.INFO, traceMessage.toString());
 		}
 
@@ -136,10 +157,9 @@ public class PostProcessorPreferencePage extends PreferencePage implements IWork
 	 *            Key used in the preference store.
 	 * @param currentSelectedEngines
 	 *            Engines to store.
-	 * @param defaultConf
-	 *            Default configuration for this type of engines.
 	 */
-	private <T> void setEnginePreferences(String preferenceKey, Set<IItemDescriptor<T>> currentSelectedEngines) {
+	private void setEnginePreferences(String preferenceKey,
+			Set<IItemDescriptor<IPostProcessor.Descriptor>> currentSelectedEngines) {
 		if (currentSelectedEngines != null && currentSelectedEngines.size() > 0) {
 			Iterable<String> identifiers = Iterables.transform(currentSelectedEngines,
 					new Function<IItemDescriptor<?>, String>() {
diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/impl/GroupsInteractiveContent.java b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/impl/GroupsInteractiveContent.java
new file mode 100644
index 000000000..9cf489815
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/impl/GroupsInteractiveContent.java
@@ -0,0 +1,292 @@
+/*******************************************************************************
+ * Copyright (c) 2014 Obeo.
+ * 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:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.rcp.ui.internal.preferences.impl;
+
+import com.google.common.collect.Lists;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.emf.compare.rcp.internal.extension.IItemDescriptor;
+import org.eclipse.emf.compare.rcp.ui.EMFCompareRCPUIPlugin;
+import org.eclipse.emf.compare.rcp.ui.internal.EMFCompareRCPUIMessages;
+import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider;
+import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider.Descriptor;
+import org.eclipse.jface.viewers.ISelection;
+import org.eclipse.jface.viewers.ISelectionChangedListener;
+import org.eclipse.jface.viewers.IStructuredSelection;
+import org.eclipse.jface.viewers.ListViewer;
+import org.eclipse.jface.viewers.SelectionChangedEvent;
+import org.eclipse.jface.viewers.StructuredSelection;
+import org.eclipse.jface.viewers.StructuredViewer;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.events.SelectionEvent;
+import org.eclipse.swt.events.SelectionListener;
+import org.eclipse.swt.layout.GridData;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.layout.RowLayout;
+import org.eclipse.swt.widgets.Button;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Group;
+import org.eclipse.swt.widgets.Text;
+
+/**
+ * Interactive content used for {@link IDifferenceGroupProvider} preferences.
+ * 
+ * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
+ */
+public class GroupsInteractiveContent {
+
+	/**
+	 * Listener to update description text
+	 * 
+	 * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
+	 */
+	private final class DescriptionListener implements ISelectionChangedListener {
+
+		public void selectionChanged(SelectionChangedEvent event) {
+			ISelection selection = event.getSelection();
+			if (selection instanceof IStructuredSelection) {
+				IStructuredSelection structSelection = (IStructuredSelection)selection;
+				Object selected = structSelection.getFirstElement();
+				if (selected instanceof IItemDescriptor<?>) {
+					IItemDescriptor<?> desc = (IItemDescriptor<?>)selected;
+					String description = desc.getDescription();
+					descriptionText.setText(description);
+				}
+			}
+
+		}
+	}
+
+	/** Down icon picture. */
+	private static final String ENABLE_DOWN_IMG = "icons/full/pref16/down.gif"; //$NON-NLS-1$
+
+	/** Up icon picture. */
+	private static final String ENABLE_UP_IMG = "icons/full/pref16/up.gif"; //$NON-NLS-1$
+
+	/** Text that shall be updated with the description of the viewer. */
+	private final Text descriptionText;
+
+	private ArrayList<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> descriptors;
+
+	private Button downButton;
+
+	private Button upButton;
+
+	/** Viewer of {@link IItemDescriptor}. */
+	private ListViewer viewer;
+
+	/** Composite holding the viewer. */
+	private final Composite viewerCompsite;
+
+	public GroupsInteractiveContent(Composite parent) {
+		super();
+		Composite containerComposite = new Composite(parent, SWT.NONE);
+		containerComposite.setLayout(new GridLayout(1, false));
+		containerComposite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true, 1, 1));
+
+		Composite interactiveComposite = new Composite(containerComposite, SWT.BORDER);
+		interactiveComposite.setLayout(new GridLayout(2, false));
+		interactiveComposite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true, 1, 1));
+
+		// Engine chooser composite
+		this.viewerCompsite = new Composite(interactiveComposite, SWT.NONE);
+		viewerCompsite.setLayout(new GridLayout(1, true));
+		viewerCompsite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true, 1, 1));
+		// Descriptor engine Text
+		createButtonComposite(interactiveComposite);
+		this.descriptionText = createDescriptionComposite(interactiveComposite);
+	}
+
+	/**
+	 * Creates the composite for up and down button.
+	 * 
+	 * @param parent
+	 */
+	private void createButtonComposite(Composite parent) {
+		Composite buttonComposite = new Composite(parent, SWT.NONE);
+		GridData layoutData = new GridData(SWT.LEFT, SWT.CENTER, false, true, 1, 1);
+		buttonComposite.setLayoutData(layoutData);
+		buttonComposite.setLayout(new RowLayout(SWT.VERTICAL));
+		upButton = new Button(buttonComposite, SWT.NONE);
+		upButton.setImage(EMFCompareRCPUIPlugin.getImage(ENABLE_UP_IMG));
+		upButton.addSelectionListener(new SelectionListener() {
+
+			public void widgetDefaultSelected(SelectionEvent e) {
+
+			}
+
+			public void widgetSelected(SelectionEvent e) {
+				if (upButton.equals(e.getSource())) {
+					IItemDescriptor<Descriptor> selection = getCurrentSelection();
+					int index = descriptors.indexOf(selection);
+					descriptors.remove(selection);
+					int newIndex = index - 1;
+					if (newIndex <= descriptors.size()) {
+						descriptors.add(newIndex, selection);
+						setViewerInput(descriptors);
+						select(selection);
+					}
+				}
+			}
+		});
+		downButton = new Button(buttonComposite, SWT.NONE);
+		downButton.addSelectionListener(new SelectionListener() {
+
+			public void widgetDefaultSelected(SelectionEvent e) {
+
+			}
+
+			public void widgetSelected(SelectionEvent e) {
+				if (downButton.equals(e.getSource())) {
+					IItemDescriptor<Descriptor> selection = getCurrentSelection();
+					int index = descriptors.indexOf(selection);
+					descriptors.remove(selection);
+					int newIndex = index + 1;
+					if (newIndex <= descriptors.size()) {
+						descriptors.add(newIndex, selection);
+						setViewerInput(descriptors);
+						select(selection);
+					}
+				}
+			}
+		});
+
+		downButton.setImage(EMFCompareRCPUIPlugin.getImage(ENABLE_DOWN_IMG));
+
+	}
+
+	/**
+	 * Composite for description. This composite holds the text widget that will update with the current
+	 * selection
+	 * 
+	 * @param composite
+	 * @return
+	 */
+	private Text createDescriptionComposite(Composite composite) {
+		Group descriptionComposite = new Group(composite, SWT.BORDER);
+		descriptionComposite.setText(EMFCompareRCPUIMessages
+				.getString("InteractiveUIContent.DESCRIPTION_COMPOSITE_LABEL")); //$NON-NLS-1$
+		descriptionComposite.setLayout(new GridLayout(1, false));
+		descriptionComposite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, false, 2, 1));
+		Text engineDescriptionText = new Text(descriptionComposite, SWT.WRAP | SWT.MULTI);
+		engineDescriptionText.setBackground(Display.getCurrent().getSystemColor(SWT.COLOR_WIDGET_BACKGROUND));
+		GridData layoutData = new GridData(SWT.FILL, SWT.FILL, true, false, 2, 1);
+		layoutData.heightHint = 50;
+		engineDescriptionText.setLayoutData(layoutData);
+		engineDescriptionText.setEditable(false);
+		return engineDescriptionText;
+	}
+
+	@SuppressWarnings("unchecked")
+	private IItemDescriptor<IDifferenceGroupProvider.Descriptor> getCurrentSelection() {
+		final ISelection selection = viewer.getSelection();
+		if (selection instanceof IStructuredSelection) {
+			final IStructuredSelection structSelection = (IStructuredSelection)selection;
+			final Object first = structSelection.getFirstElement();
+			if (first instanceof IItemDescriptor<?>) {
+				// secure due to Object structure.
+				return (IItemDescriptor<IDifferenceGroupProvider.Descriptor>)first;
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * @return The ordered list of {@link IItemDescriptor}.
+	 */
+	public List<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> getItems() {
+		return descriptors;
+	}
+
+	/**
+	 * @return The composite holding the viewer.
+	 */
+	public Composite getViewerComposite() {
+		return viewerCompsite;
+	}
+
+	private boolean isFirst(Object o) {
+		if (descriptors != null && !descriptors.isEmpty()) {
+			return descriptors.get(0).equals(o);
+		}
+		return false;
+	}
+
+	private boolean isLast(Object o) {
+		if (descriptors != null && !descriptors.isEmpty()) {
+			return descriptors.get(descriptors.size() - 1).equals(o);
+		}
+		return false;
+	}
+
+	/**
+	 * Handles a selection in the viewer. Updates related components.
+	 * 
+	 * @param descriptor
+	 */
+	public void select(IItemDescriptor<IDifferenceGroupProvider.Descriptor> descriptor) {
+		// Update viewer
+		viewer.setSelection(new StructuredSelection(descriptor), true);
+		updateLinkedElements(descriptor);
+	}
+
+	/**
+	 * Sets the input for interactive content.
+	 * 
+	 * @param input
+	 */
+	public void setViewerInput(List<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> input) {
+		if (viewer != null) {
+			this.descriptors = Lists.newArrayList(input);
+			viewer.setInput(descriptors);
+		} else {
+			EMFCompareRCPUIPlugin.getDefault().log(IStatus.ERROR,
+					"Please initialize the viewer before setting input"); //$NON-NLS-1$
+		}
+	}
+
+	/**
+	 * @param viewer
+	 *            A {@link StructuredViewer} of {@link IItemDescriptor}
+	 */
+	public void setViewer(ListViewer inputViewer) {
+		this.viewer = inputViewer;
+		viewer.addSelectionChangedListener(new DescriptionListener());
+		viewer.addSelectionChangedListener(new ISelectionChangedListener() {
+
+			public void selectionChanged(SelectionChangedEvent event) {
+				IItemDescriptor<?> selection = getCurrentSelection();
+				if (selection == null) {
+					upButton.setEnabled(false);
+					downButton.setEnabled(false);
+				} else {
+					upButton.setEnabled(!isFirst(selection));
+					downButton.setEnabled(!isLast(selection));
+				}
+			}
+
+		});
+	}
+
+	/**
+	 * Updates linked element in
+	 * 
+	 * @param descriptor
+	 */
+	private void updateLinkedElements(IItemDescriptor<IDifferenceGroupProvider.Descriptor> descriptor) {
+		// Update description
+		descriptionText.setText(descriptor.getDescription());
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/InteractiveUIContent.java b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/impl/InteractiveUIContent.java
index ad0cb168b..a26a31014 100644
--- a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/InteractiveUIContent.java
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/impl/InteractiveUIContent.java
@@ -8,7 +8,7 @@
  * Contributors:
  *     Obeo - initial API and implementation
  *******************************************************************************/
-package org.eclipse.emf.compare.rcp.ui.internal.preferences;
+package org.eclipse.emf.compare.rcp.ui.internal.preferences.impl;
 
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap;
@@ -28,6 +28,7 @@ import org.eclipse.emf.compare.rcp.internal.extension.impl.ItemUtil;
 import org.eclipse.emf.compare.rcp.ui.internal.EMFCompareRCPUIMessages;
 import org.eclipse.emf.compare.rcp.ui.internal.configuration.ui.AbstractConfigurationUI;
 import org.eclipse.emf.compare.rcp.ui.internal.configuration.ui.IConfigurationUIFactory;
+import org.eclipse.emf.compare.rcp.ui.internal.preferences.DataHolder;
 import org.eclipse.jface.databinding.viewers.IViewerObservableSet;
 import org.eclipse.jface.databinding.viewers.ViewersObservables;
 import org.eclipse.jface.dialogs.MessageDialog;
@@ -38,7 +39,6 @@ import org.eclipse.jface.viewers.ICheckStateListener;
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.jface.viewers.ISelectionChangedListener;
 import org.eclipse.jface.viewers.IStructuredSelection;
-import org.eclipse.jface.viewers.LabelProvider;
 import org.eclipse.jface.viewers.SelectionChangedEvent;
 import org.eclipse.jface.viewers.StructuredSelection;
 import org.eclipse.jface.viewers.StructuredViewer;
@@ -73,7 +73,10 @@ import org.osgi.service.prefs.Preferences;
  * 
  * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
  */
-public class InteractiveUIContent {
+public final class InteractiveUIContent {
+
+	/** Height hint for description composite. */
+	private static final int DESCRIPTION_COMPOSITE_HEIGHT_HINT = 50;
 
 	/** Text that will be updated with the description of the viewer. */
 	private final Text descriptionText;
@@ -93,6 +96,16 @@ public class InteractiveUIContent {
 	/** List of all {@link AbstractConfigurationUI} that are linked to this viewer. */
 	private final Map<String, AbstractConfigurationUI> configurators = new HashMap<String, AbstractConfigurationUI>();
 
+	/**
+	 * Constructor.
+	 * 
+	 * @param parent
+	 *            Composite parent holding this interactive content.
+	 * @param hasDescription
+	 *            Set to true if this has a description label that react to viewer selection.
+	 * @param hasConfiguration
+	 *            set to true if this has a configuration composite that react to viewer selection.
+	 */
 	private InteractiveUIContent(Composite parent, boolean hasDescription, boolean hasConfiguration) {
 		super();
 		Composite contentComposite = new Composite(parent, SWT.NONE);
@@ -131,12 +144,14 @@ public class InteractiveUIContent {
 	}
 
 	/**
-	 * Add a configuration to this Interactive content.
+	 * Adds a configuration to this Interactive content.
 	 * 
 	 * @param id
 	 *            Id of the item to configure
 	 * @param configuratorfactory
 	 *            Factory for the configuration
+	 * @param pref
+	 *            Preference store that will hold this {@link IConfigurationUIFactory} value.
 	 */
 	public void addConfigurator(String id, IConfigurationUIFactory configuratorfactory, Preferences pref) {
 		AbstractConfigurationUI configurator = configuratorfactory.createUI(configurationComposite, SWT.NONE,
@@ -145,31 +160,34 @@ public class InteractiveUIContent {
 	}
 
 	/**
-	 * Check one element in the viewer
+	 * Checks one element in the viewer.
 	 * 
 	 * @param descriptor
+	 *            element to check.
 	 */
 	public void checkElement(IItemDescriptor<?> descriptor) {
 		viewer.setCheckedElements(new Object[] {descriptor });
 	}
 
 	/**
-	 * Check multiple element in the viewer. (Only use if multiple selection is allowed)
+	 * Checks multiple element in the viewer. (Only use if multiple selection is allowed)
 	 * 
 	 * @param descriptors
+	 *            elements to check.
 	 */
 	public void checkElements(IItemDescriptor<?>[] descriptors) {
 		viewer.setCheckedElements(descriptors);
 	}
 
 	/**
-	 * Create the composite that will hold all configurations for a tab.
+	 * Creates the composite that will hold all configurations for a tab.
 	 * 
 	 * @param composite
-	 * @return
+	 *            Main composite
+	 * @return Group that will hold configurations in a stack layout.
 	 */
 	private Group createConfigComposite(Composite composite) {
-		Group confComposite = new Group(composite, SWT.NONE);
+		Group confComposite = new Group(composite, SWT.BORDER);
 		confComposite.setText(EMFCompareRCPUIMessages
 				.getString("InteractiveUIContent.CONFIGURATION_COMPOSITE_LABEL")); //$NON-NLS-1$
 		StackLayout layout = new StackLayout();
@@ -182,14 +200,15 @@ public class InteractiveUIContent {
 	}
 
 	/**
-	 * Composite for description. This composite hold the text widget that will update with the current
-	 * selection
+	 * Composite for description. This composite holds the text widget that will be updated with the current
+	 * selection.
 	 * 
 	 * @param composite
-	 * @return
+	 *            Main composite.
+	 * @return Text that will hold viewer selection description.
 	 */
 	private Text createDescriptionComposite(Composite composite) {
-		Group descriptionComposite = new Group(composite, SWT.NONE);
+		Group descriptionComposite = new Group(composite, SWT.BORDER);
 		descriptionComposite.setText(EMFCompareRCPUIMessages
 				.getString("InteractiveUIContent.DESCRIPTION_COMPOSITE_LABEL")); //$NON-NLS-1$
 		descriptionComposite.setLayout(new GridLayout(1, false));
@@ -197,7 +216,7 @@ public class InteractiveUIContent {
 		Text engineDescriptionText = new Text(descriptionComposite, SWT.WRAP | SWT.MULTI);
 		engineDescriptionText.setBackground(Display.getCurrent().getSystemColor(SWT.COLOR_WIDGET_BACKGROUND));
 		GridData layoutData = new GridData(SWT.FILL, SWT.FILL, true, false, 1, 1);
-		layoutData.heightHint = 50;
+		layoutData.heightHint = DESCRIPTION_COMPOSITE_HEIGHT_HINT;
 		engineDescriptionText.setLayoutData(layoutData);
 		engineDescriptionText.setEditable(false);
 		return engineDescriptionText;
@@ -211,6 +230,8 @@ public class InteractiveUIContent {
 	}
 
 	/**
+	 * Gets the viewer.
+	 * 
 	 * @return The viewer.
 	 */
 	private CheckboxTableViewer getViewer() {
@@ -218,6 +239,8 @@ public class InteractiveUIContent {
 	}
 
 	/**
+	 * Returns the composite that will hold the viewer.
+	 * 
 	 * @return The composite holding the viewer.
 	 */
 	private Composite getViewerComposite() {
@@ -225,9 +248,10 @@ public class InteractiveUIContent {
 	}
 
 	/**
-	 * Handle a selection in the viewer. Update related components.
+	 * Handles a selection in the viewer. Update related components.
 	 * 
 	 * @param descriptor
+	 *            Item to select.
 	 */
 	public void select(IItemDescriptor<?> descriptor) {
 		// Update viewer
@@ -236,7 +260,9 @@ public class InteractiveUIContent {
 	}
 
 	/**
-	 * @param viewer
+	 * Sets the viewer in the interactive content.
+	 * 
+	 * @param inputViewer
 	 *            A {@link StructuredViewer} of {@link IItemDescriptor}
 	 */
 	public void setViewer(CheckboxTableViewer inputViewer) {
@@ -248,9 +274,10 @@ public class InteractiveUIContent {
 	}
 
 	/**
-	 * Update linked element in
+	 * Updates the linked element in this interactive content.
 	 * 
 	 * @param descriptor
+	 *            Item used as input to get information for satellite elements.
 	 */
 	private void updateLinkedElements(IItemDescriptor<?> descriptor) {
 		// Update description
@@ -260,6 +287,12 @@ public class InteractiveUIContent {
 		}
 	}
 
+	/**
+	 * Updates the configuration composite.
+	 * 
+	 * @param descriptor
+	 *            New descriptor.
+	 */
 	private void updateConfigurationComposite(IItemDescriptor<?> descriptor) {
 		StackLayout stackLayout = (StackLayout)configurationComposite.getLayout();
 		if (configurators.containsKey(descriptor.getID())) {
@@ -271,18 +304,35 @@ public class InteractiveUIContent {
 	}
 
 	/**
-	 * This listener updates the Data Holder and for that only one element can be checked at a time.
+	 * This listener updates the Data Holder.
+	 * <p>
+	 * With this listener, only one element can be checked at a time
+	 * </p>
 	 * 
 	 * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
 	 * @param <T>
+	 *            Type of item.
 	 */
 	private static final class SingleCheckListener<T> implements ICheckStateListener {
+		/** Data holder. */
 		private final DataHolder<T> dataObject;
 
+		/** Viewer. */
 		private final CheckboxTableViewer descriptorViewer;
 
+		/** Shell. */
 		private final Shell shell;
 
+		/**
+		 * Constructor.
+		 * 
+		 * @param dataObject
+		 *            Data holder.
+		 * @param descriptorViewer
+		 *            Viewer
+		 * @param shell
+		 *            Shell.
+		 */
 		private SingleCheckListener(DataHolder<T> dataObject, CheckboxTableViewer descriptorViewer,
 				Shell shell) {
 			this.dataObject = dataObject;
@@ -290,6 +340,9 @@ public class InteractiveUIContent {
 			this.shell = shell;
 		}
 
+		/**
+		 * {@inheritDoc}
+		 */
 		public void checkStateChanged(CheckStateChangedEvent event) {
 			Object element = event.getElement();
 			if (event.getChecked()) {
@@ -319,25 +372,31 @@ public class InteractiveUIContent {
 	 * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
 	 */
 	private final class ConfigurationListener implements ISelectionChangedListener {
+		/**
+		 * {@inheritDoc}
+		 */
 		public void selectionChanged(SelectionChangedEvent event) {
 			ISelection selection = event.getSelection();
 			if (selection instanceof IStructuredSelection) {
 				IStructuredSelection structSelection = (IStructuredSelection)selection;
 				Object selected = structSelection.getFirstElement();
 				if (selected instanceof IItemDescriptor<?>) {
-					updateLinkedElements(((IItemDescriptor<?>)selected));
+					updateLinkedElements((IItemDescriptor<?>)selected);
 				}
 			}
 		}
 	}
 
 	/**
-	 * Listener to update description text
+	 * Listener used to update description text.
 	 * 
 	 * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
 	 */
 	private final class DescriptionListener implements ISelectionChangedListener {
 
+		/**
+		 * {@inheritDoc}
+		 */
 		public void selectionChanged(SelectionChangedEvent event) {
 			ISelection selection = event.getSelection();
 			if (selection instanceof IStructuredSelection) {
@@ -354,25 +413,6 @@ public class InteractiveUIContent {
 	}
 
 	/**
-	 * Label provider for {@link ILabeledItemDescriptor}
-	 * 
-	 * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
-	 */
-	private static final class EngineDescriptorLabelProvider extends LabelProvider {
-		/**
-		 * {@inheritDoc}
-		 */
-		@Override
-		public String getText(Object element) {
-			if (element instanceof IItemDescriptor<?>) {
-				IItemDescriptor<?> desc = (IItemDescriptor<?>)element;
-				return desc.getLabel();
-			}
-			return super.getText(element);
-		}
-	}
-
-	/**
 	 * Builder for an Interactive UI.
 	 * 
 	 * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
@@ -394,10 +434,10 @@ public class InteractiveUIContent {
 		private Map<String, IConfigurationUIFactory> configurationUIRegistry;
 
 		/** Set of elements to check by default. */
-		private Set<IItemDescriptor<T>> defaultCheck = null;
+		private Set<IItemDescriptor<T>> defaultCheck;
 
 		/** Element to select by default. */
-		private IItemDescriptor<T> defaultSelection = null;
+		private IItemDescriptor<T> defaultSelection;
 
 		/** Object holding data representing the current status of the interactive content. */
 		private DataHolder<T> dataHolder;
@@ -415,8 +455,6 @@ public class InteractiveUIContent {
 		 *            Holding composite of all the structure.
 		 * @param registry
 		 *            Item registry holding input of the viewer.
-		 * @param dataHolder
-		 *            Object holding data representing the current status of the interactive content.
 		 */
 		public InteractiveUIBuilder(Composite parent, IItemRegistry<T> registry) {
 			super();
@@ -425,24 +463,25 @@ public class InteractiveUIContent {
 		}
 
 		/**
-		 * Set a dataHolder that will be synchronized with the checked element. If this isSimple then
-		 * {@link DataHolder#simpleData} is filled. else {@link DataHolder#data} is filled
+		 * Sets a dataHolder that will be synchronized with the checked element.
 		 * 
-		 * @param dataHolder
-		 * @return
+		 * @param newDataHolder
+		 *            DataHolder.
+		 * @return {@link InteractiveUIBuilder}
 		 */
-		public InteractiveUIBuilder<T> setHoldingData(DataHolder<T> dataHolder) {
-			this.dataHolder = dataHolder;
+		public InteractiveUIBuilder<T> setHoldingData(DataHolder<T> newDataHolder) {
+			this.dataHolder = newDataHolder;
 			return this;
 		}
 
 		/**
-		 * Key of the node to get the {@link Preferences} to retrieve {@link IConfigurationUIFactory}. See
-		 * {@link ItemUtil#getConfigurationPreferenceNode(String, String)} (needed is ConfigurationUIRegistry
-		 * is provided)
+		 * Node key used to get the {@link Preferences} to retrieve {@link IConfigurationUIFactory}. See
+		 * {@link ItemUtil#getConfigurationPreferenceNode(String, String)} (needed if a
+		 * ConfigurationUIRegistry has been provided)
 		 * 
 		 * @param key
-		 * @return
+		 *            .
+		 * @return {@link InteractiveUIBuilder}
 		 */
 		public InteractiveUIBuilder<T> setConfigurationNodeKey(String key) {
 			this.configurationNodeKey = key;
@@ -450,10 +489,11 @@ public class InteractiveUIContent {
 		}
 
 		/**
-		 * Registry of of {@link IConfigurationUIFactory} to filled the configuraiton composite.
+		 * Registry of {@link IConfigurationUIFactory} used to fill the configuration composite.
 		 * 
 		 * @param configuratorUIRegistry
-		 * @return
+		 *            .
+		 * @return {@link InteractiveUIBuilder}
 		 */
 		public InteractiveUIBuilder<T> setConfiguratorUIRegistry(
 				Map<String, IConfigurationUIFactory> configuratorUIRegistry) {
@@ -462,54 +502,58 @@ public class InteractiveUIContent {
 		}
 
 		/**
-		 * Set the default element to check. (A singleton is this is set to simple
+		 * Sets the default element to check. (A singleton if "this" is set to simple
 		 * {@link InteractiveUIBuilder#setSimple(boolean)}
 		 * 
-		 * @param defaultCheck
-		 * @return
+		 * @param newDefaultCheck
+		 *            .
+		 * @return InteractiveUIBuilder
 		 */
-		public InteractiveUIBuilder<T> setDefaultCheck(Set<IItemDescriptor<T>> defaultCheck) {
-			this.defaultCheck = defaultCheck;
+		public InteractiveUIBuilder<T> setDefaultCheck(Set<IItemDescriptor<T>> newDefaultCheck) {
+			this.defaultCheck = newDefaultCheck;
 			return this;
 		}
 
 		/**
 		 * Set the default element to select.
 		 * 
-		 * @param defaultSelection
-		 * @return
+		 * @param newDefaultSelection
+		 *            .
+		 * @return InteractiveUIBuilder
 		 */
-		public InteractiveUIBuilder<T> setDefaultSelection(IItemDescriptor<T> defaultSelection) {
-			this.defaultSelection = defaultSelection;
+		public InteractiveUIBuilder<T> setDefaultSelection(IItemDescriptor<T> newDefaultSelection) {
+			this.defaultSelection = newDefaultSelection;
 			return this;
 		}
 
 		/**
-		 * Set to true if this need to create a description field.
+		 * Set to true if "this" needs to create a description field.
 		 * 
-		 * @param hasDescription
-		 * @return
+		 * @param newHasDescription
+		 *            .
+		 * @return {@link InteractiveUIBuilder}
 		 */
-		public InteractiveUIBuilder<T> setHasDescription(boolean hasDescription) {
-			this.hasDescription = hasDescription;
+		public InteractiveUIBuilder<T> setHasDescription(boolean newHasDescription) {
+			this.hasDescription = newHasDescription;
 			return this;
 		}
 
 		/**
-		 * Set to true if the viewer can only have only one element check at a time.
+		 * Set to true if the viewer can only have only one element checked at a time.
 		 * 
-		 * @param isSimple
-		 * @return
+		 * @param newIsSimple
+		 *            .
+		 * @return {@link InteractiveUIBuilder}
 		 */
-		public InteractiveUIBuilder<T> setSimple(boolean isSimple) {
-			this.isSimple = isSimple;
+		public InteractiveUIBuilder<T> setSimple(boolean newIsSimple) {
+			this.isSimple = newIsSimple;
 			return this;
 		}
 
 		/**
-		 * Build a new {@link InteractiveUI}
+		 * Build a new {@link InteractiveUI}.
 		 * 
-		 * @return
+		 * @return InteractiveUIContent
 		 */
 		public InteractiveUIContent build() {
 			// If simple only one element check at a time
@@ -533,6 +577,13 @@ public class InteractiveUIContent {
 			return interactiveUI;
 		}
 
+		/**
+		 * Initializes the viewer.
+		 * 
+		 * @param interactiveUI
+		 *            .
+		 * @return CheckboxTableViewer
+		 */
 		private CheckboxTableViewer createViewer(final InteractiveUIContent interactiveUI) {
 			int style = SWT.BORDER | SWT.V_SCROLL | SWT.FULL_SELECTION;
 			if (isSimple) {
@@ -542,12 +593,18 @@ public class InteractiveUIContent {
 					.getViewerComposite(), style);
 			interactiveUI.setViewer(descriptorViewer);
 			descriptorViewer.setContentProvider(ArrayContentProvider.getInstance());
-			descriptorViewer.setLabelProvider(new EngineDescriptorLabelProvider());
+			descriptorViewer.setLabelProvider(new ItemDescriptorLabelProvider());
 			GridData gd = new GridData(SWT.FILL, SWT.FILL, true, true, 1, 1);
 			descriptorViewer.getControl().setLayoutData(gd);
 			return descriptorViewer;
 		}
 
+		/**
+		 * Creates the configuration composite.
+		 * 
+		 * @param interactiveUI
+		 *            .
+		 */
 		private void createConfigurationComposite(final InteractiveUIContent interactiveUI) {
 			// Init configuration elements
 			for (IItemDescriptor<T> item : registry.getItemDescriptors()) {
@@ -560,6 +617,14 @@ public class InteractiveUIContent {
 			}
 		}
 
+		/**
+		 * Initializes and binds interactive content with the data holder value.
+		 * 
+		 * @param interactiveUI
+		 *            .
+		 * @param descriptorViewer
+		 *            .
+		 */
 		private void bindAndInit(final InteractiveUIContent interactiveUI,
 				CheckboxTableViewer descriptorViewer) {
 			if (defaultSelection != null) {
@@ -581,11 +646,17 @@ public class InteractiveUIContent {
 						dataHolder.setData(defaultCheck);
 					}
 					// Bind data
-					bindMultipleData(DataHolder.DATA_FIELD_NAME, interactiveUI.getViewer(), dataHolder);
+					bindMultipleData(interactiveUI.getViewer(), dataHolder);
 				}
 			}
 		}
 
+		/**
+		 * Sets the viewer input.
+		 * 
+		 * @param descriptorViewer
+		 *            .
+		 */
 		private void setViewerInput(CheckboxTableViewer descriptorViewer) {
 			List<IItemDescriptor<T>> itemDescriptors = registry.getItemDescriptors();
 			Collections.sort(itemDescriptors);
@@ -593,19 +664,19 @@ public class InteractiveUIContent {
 		}
 
 		/**
-		 * Bind UI to data object.
+		 * Binds UI to data object.
 		 * 
-		 * @param engineBindingProperty
 		 * @param descriptorViewer
+		 *            .
 		 * @param dataObject
+		 *            The data holder.
 		 */
-		private void bindMultipleData(String engineBindingProperty, CheckboxTableViewer descriptorViewer,
-				final DataHolder<T> dataObject) {
+		private void bindMultipleData(CheckboxTableViewer descriptorViewer, final DataHolder<T> dataObject) {
 			DataBindingContext ctx = new DataBindingContext();
 			// Bind the button with the corresponding field in data
 			IViewerObservableSet target = ViewersObservables.observeCheckedElements(descriptorViewer,
 					IItemDescriptor.class);
-			IObservableSet model = PojoProperties.set(DataHolder.class, engineBindingProperty).observe(
+			IObservableSet model = PojoProperties.set(DataHolder.class, DataHolder.DATA_FIELD_NAME).observe(
 					dataObject);
 
 			ctx.bindSet(target, model);
diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/impl/ItemDescriptorLabelProvider.java b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/impl/ItemDescriptorLabelProvider.java
new file mode 100644
index 000000000..84d5c57cd
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/preferences/impl/ItemDescriptorLabelProvider.java
@@ -0,0 +1,33 @@
+/*******************************************************************************
+ * Copyright (c) 2014 Obeo.
+ * 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:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.rcp.ui.internal.preferences.impl;
+
+import org.eclipse.emf.compare.rcp.internal.extension.IItemDescriptor;
+import org.eclipse.jface.viewers.LabelProvider;
+
+/**
+ * Label provider for {@link IItemDescriptor}.
+ * 
+ * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
+ */
+public class ItemDescriptorLabelProvider extends LabelProvider {
+	/**
+	 * {@inheritDoc}
+	 */
+	@Override
+	public String getText(Object element) {
+		if (element instanceof IItemDescriptor<?>) {
+			IItemDescriptor<?> desc = (IItemDescriptor<?>)element;
+			return desc.getLabel();
+		}
+		return super.getText(element);
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/structuremergeviewer/groups/impl/DifferenceGroupManager.java b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/structuremergeviewer/groups/impl/DifferenceGroupManager.java
new file mode 100644
index 000000000..e6ea2a338
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/structuremergeviewer/groups/impl/DifferenceGroupManager.java
@@ -0,0 +1,258 @@
+/******************************************************************************

+ * Copyright (c) 2014 Obeo.

+ * 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:

+ *     Obeo - initial API and implementation

+ *******************************************************************************/

+package org.eclipse.emf.compare.rcp.ui.internal.structuremergeviewer.groups.impl;

+

+import com.google.common.base.Predicate;

+import com.google.common.collect.Iterables;

+import com.google.common.collect.Lists;

+import com.google.common.collect.Sets;

+import com.google.common.collect.Sets.SetView;

+

+import java.util.Collections;

+import java.util.HashSet;

+import java.util.Iterator;

+import java.util.List;

+

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

+import org.eclipse.emf.compare.rcp.internal.extension.IItemDescriptor;

+import org.eclipse.emf.compare.rcp.internal.extension.IItemRegistry;

+import org.eclipse.emf.compare.rcp.internal.extension.impl.ItemUtil;

+import org.eclipse.emf.compare.rcp.internal.tracer.TracingConstant;

+import org.eclipse.emf.compare.rcp.ui.EMFCompareRCPUIPlugin;

+import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider;

+import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider.ComparisonType;

+import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider.Descriptor;

+import org.osgi.service.prefs.Preferences;

+

+/**

+ * This manager can be used to modify EMF Compare UI behavior regarding groups.

+ * <p>

+ * This manager can override the rank of groups. For example, it can be used to define a default group that

+ * will be used by EMF Compare UI.

+ * </p>

+ * 

+ * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>

+ */

+public class DifferenceGroupManager {

+

+	/** Prefix for preferences. */

+	private static final String EMFCOMPARE_RCP_UI_PREFIX = "org.eclipse.emf.compare.rcp.ui."; //$NON-NLS-1$

+

+	/** Ordered list of groups for two way comparison. */

+	private static final String TWO_WAY_GROUP_RANKING = EMFCOMPARE_RCP_UI_PREFIX + "groups.2way.ranking"; //$NON-NLS-1$

+

+	/** Ordered list of groups for three way comparison. */

+	private static final String THREE_WAY_GROUP_RANKING = EMFCOMPARE_RCP_UI_PREFIX + "groups.3way.ranking"; //$NON-NLS-1$

+

+	/** Preferences holding preference values. */

+	private final Preferences preferences;

+

+	/** Registry of {@link IDifferenceGroupProvider.Descriptor}. */

+	private final IItemRegistry<IDifferenceGroupProvider.Descriptor> registry;

+

+	private static final Predicate<IItemDescriptor<Descriptor>> TWO_WAY_FILTER = new Predicate<IItemDescriptor<Descriptor>>() {

+

+		public boolean apply(IItemDescriptor<Descriptor> descriptor) {

+			if (descriptor == null) {

+				return false;

+			}

+			ComparisonType type = descriptor.getItem().getType();

+			return type == ComparisonType.BOTH || type == ComparisonType.TWO_WAY;

+		}

+	};

+

+	private static final Predicate<IItemDescriptor<Descriptor>> THREE_WAY_FILTER = new Predicate<IItemDescriptor<Descriptor>>() {

+

+		public boolean apply(IItemDescriptor<Descriptor> descriptor) {

+			if (descriptor == null) {

+				return false;

+			}

+			ComparisonType type = descriptor.getItem().getType();

+			return type == ComparisonType.BOTH || type == ComparisonType.THREE_WAY;

+		}

+	};

+

+	/**

+	 * Constructor.

+	 * 

+	 * @param preferences

+	 *            Preferences holding preference values.

+	 * @param registry

+	 *            Registry of {@link IDifferenceGroupProvider.Descriptor}.

+	 */

+	public DifferenceGroupManager(Preferences preferences,

+			IItemRegistry<IDifferenceGroupProvider.Descriptor> registry) {

+		super();

+		this.preferences = preferences;

+		this.registry = registry;

+	}

+

+	/**

+	 * Gets the current value of the group ranking.

+	 * 

+	 * @param preferenceKey

+	 *            Preference key use to retrieve the value in preferences.

+	 * @param defaultOrder

+	 *            The default ranking.

+	 * @return A ordered {@link List} of {@link IItemDescriptor}.

+	 */

+	private List<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> getCurrent(String preferenceKey,

+			List<IItemDescriptor<Descriptor>> defaultOrder) {

+		return getOrderedItems(defaultOrder, registry, preferenceKey);

+	}

+

+	/**

+	 * Gets the current group order.

+	 * 

+	 * @param isThreeWay

+	 *            True if three way comparison, false otherwise.

+	 * @return Ordered {@link List} of {@link IDifferenceGroupProvider.Descriptor}.

+	 */

+	public List<IItemDescriptor<Descriptor>> getCurrentGroupRanking(boolean isThreeWay) {

+		return getCurrent(getGroupPreferenceKey(isThreeWay), getDefaultRankingConfiguration(isThreeWay));

+	}

+

+	/**

+	 * Gets the default groups order.

+	 * 

+	 * @param isThreeWay

+	 *            True if three way comparison, false otherwise.

+	 * @return Ordered {@link List} of {@link IDifferenceGroupProvider.Descriptor}.

+	 */

+	public List<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> getDefaultRankingConfiguration(

+			boolean isThreeWay) {

+		final Iterable<IItemDescriptor<Descriptor>> groups;

+		if (isThreeWay) {

+			groups = Iterables.filter(registry.getItemDescriptors(), THREE_WAY_FILTER);

+		} else {

+

+			groups = Iterables.filter(registry.getItemDescriptors(), TWO_WAY_FILTER);

+		}

+		List<IItemDescriptor<Descriptor>> result = Lists.newArrayList(groups);

+		Collections.sort(result);

+		return result;

+	}

+

+	/**

+	 * Gets the preference key for group ranking.

+	 * 

+	 * @param isThreeWay

+	 *            True if three way comparison.

+	 * @return They key of the group ranking preference for this type of comparison.

+	 */

+	private String getGroupPreferenceKey(boolean isThreeWay) {

+		if (isThreeWay) {

+			return THREE_WAY_GROUP_RANKING;

+		} else {

+			return TWO_WAY_GROUP_RANKING;

+		}

+	}

+

+	/**

+	 * Returns an ordered list of {@link IItemDescriptor}. The order of the list is either defined by the rank

+	 * in the registry or from preference if the rank has been overloaded. If any descriptor has been added or

+	 * removed since last modification of the preference, this method will merge the modification.

+	 * 

+	 * @param orderedDefaultDescriptor

+	 *            List of ordered default {@link IItemDescriptor}.

+	 * @param descriptorRegistry

+	 *            Registry of descriptor.

+	 * @param orderedItemPreferenceKey

+	 *            Key in preferences where are stored the new order of descriptor

+	 * @return Ordered list of descriptor.

+	 * @param <T>

+	 *            Descriptor type.

+	 */

+	private <T> List<IItemDescriptor<T>> getOrderedItems(List<IItemDescriptor<T>> orderedDefaultDescriptor,

+			IItemRegistry<T> descriptorRegistry, String orderedItemPreferenceKey) {

+		List<IItemDescriptor<T>> itemsDescriptor = ItemUtil.getItemsDescriptor(descriptorRegistry,

+				orderedItemPreferenceKey, preferences);

+

+		if (itemsDescriptor == null) {

+			itemsDescriptor = orderedDefaultDescriptor;

+		} else {

+			HashSet<IItemDescriptor<T>> descriptorFromPrefSet = Sets.newLinkedHashSet(itemsDescriptor);

+			HashSet<IItemDescriptor<T>> defaultDescriptorSet = Sets

+					.newLinkedHashSet(orderedDefaultDescriptor);

+

+			// Remove descriptor

+			SetView<IItemDescriptor<T>> descriptorToRemove = Sets.difference(descriptorFromPrefSet,

+					defaultDescriptorSet);

+			Iterables.removeAll(itemsDescriptor, descriptorToRemove);

+

+			// Add new descriptor

+			SetView<IItemDescriptor<T>> descriptorToAdd = Sets.difference(defaultDescriptorSet,

+					descriptorFromPrefSet);

+			Iterables.addAll(itemsDescriptor, descriptorToAdd);

+

+		}

+		return itemsDescriptor;

+	}

+

+	/**

+	 * Sets the ranking of Difference group provider.

+	 * 

+	 * @param descriptors

+	 *            An ordered list of {@link IItemDescriptor}.

+	 * @param isThreeWay

+	 *            True if three way comparison.

+	 */

+	public void setCurrentGroupRanking(List<IItemDescriptor<Descriptor>> descriptors, boolean isThreeWay) {

+		storeInPreferences(getGroupPreferenceKey(isThreeWay), descriptors,

+				getDefaultRankingConfiguration(isThreeWay));

+

+		// Trace preferences values

+		if (TracingConstant.CONFIGURATION_TRACING_ACTIVATED) {

+			StringBuilder builder = new StringBuilder();

+			// Print each preferences

+			builder.append("Preference ").append(getGroupPreferenceKey(isThreeWay)).append(":\n"); //$NON-NLS-1$ //$NON-NLS-2$

+			String preferenceValue = preferences.get(getGroupPreferenceKey(isThreeWay), ""); //$NON-NLS-1$

+			if (!"".equals(preferences)) { //$NON-NLS-1$

+				String[] groups = preferenceValue.split(ItemUtil.PREFERENCE_DELIMITER);

+				for (int rank = 0; rank < groups.length; rank++) {

+					builder.append(rank).append(". ").append(groups[rank]).append("\n"); //$NON-NLS-1$ //$NON-NLS-2$

+				}

+			}

+			builder.append("\n\n"); //$NON-NLS-1$

+			EMFCompareRCPUIPlugin.getDefault().log(IStatus.INFO, builder.toString());

+		}

+	}

+

+	/**

+	 * Stores the value into preferences.

+	 * 

+	 * @param preferenceKey

+	 *            Key of the preference

+	 * @param currentValue

+	 *            Current value to store

+	 * @param defaultConf

+	 *            Default value

+	 */

+	private void storeInPreferences(String preferenceKey,

+			List<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> currentValue,

+			List<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> defaultConf) {

+		if (currentValue != null && !currentValue.equals(defaultConf)) {

+			StringBuilder descriptorsKey = new StringBuilder();

+			for (Iterator<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> iterator = currentValue

+					.iterator(); iterator.hasNext();) {

+				IItemDescriptor<IDifferenceGroupProvider.Descriptor> iItemDescriptor = iterator.next();

+				descriptorsKey.append(iItemDescriptor.getID());

+				if (iterator.hasNext()) {

+					descriptorsKey.append(ItemUtil.PREFERENCE_DELIMITER);

+				}

+			}

+			preferences.put(preferenceKey, descriptorsKey.toString());

+		} else {

+			preferences.remove(preferenceKey);

+		}

+	}

+

+}

diff --git a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/structuremergeviewer/groups/impl/DifferenceGroupRegistryImpl.java b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/structuremergeviewer/groups/impl/DifferenceGroupRegistryImpl.java
index ad757210d..e5f263b61 100644
--- a/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/structuremergeviewer/groups/impl/DifferenceGroupRegistryImpl.java
+++ b/plugins/org.eclipse.emf.compare.rcp.ui/src/org/eclipse/emf/compare/rcp/ui/internal/structuremergeviewer/groups/impl/DifferenceGroupRegistryImpl.java
@@ -13,10 +13,7 @@ package org.eclipse.emf.compare.rcp.ui.internal.structuremergeviewer.groups.impl
 import static com.google.common.collect.Lists.newArrayList;

 

 import com.google.common.base.Preconditions;

-import com.google.common.base.Predicate;

 import com.google.common.collect.ImmutableList;

-import com.google.common.collect.Iterables;

-import com.google.common.collect.Lists;

 

 import java.util.Collections;

 import java.util.List;

@@ -25,13 +22,10 @@ import java.util.ListIterator;
 import org.eclipse.emf.compare.Comparison;

 import org.eclipse.emf.compare.rcp.internal.extension.IItemDescriptor;

 import org.eclipse.emf.compare.rcp.internal.extension.IItemRegistry;

-import org.eclipse.emf.compare.rcp.internal.extension.impl.ItemUtil;

 import org.eclipse.emf.compare.rcp.internal.extension.impl.WrapperItemDescriptor;

 import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider;

-import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider.ComparisonType;

 import org.eclipse.emf.compare.rcp.ui.structuremergeviewer.groups.IDifferenceGroupProvider.Descriptor;

 import org.eclipse.emf.compare.scope.IComparisonScope;

-import org.osgi.service.prefs.Preferences;

 

 /**

  * Implementation of the {@link IDifferenceGroupProvider.Descriptor.Registry}. This implementation allow user

@@ -45,44 +39,21 @@ public class DifferenceGroupRegistryImpl implements IDifferenceGroupProvider.Des
 	/** A map that associates the class name to theirs {@link IDifferenceGroupProvider.Descriptor}s. */

 	private final IItemRegistry<IDifferenceGroupProvider.Descriptor> registry;

 

-	/** Preference key for two way comparison group ranking. */

-	private final String twoWayPreferenceKey;

-

-	/** Preference key for three way comparison group ranking. */

-	private final String threeWayPrefenceKey;

-

-	/** Preferences holding ranked descriptors. */

-	private Preferences preferences;

+	/** Group manager. */

+	private DifferenceGroupManager groupManager;

 

 	/**

 	 * Constructs the registry.

 	 * 

-	 * @param twoWaygroupProviderDescriptors

+	 * @param groupManager

+	 *            {@link DifferenceGroupManager} use to handle groups.

+	 * @param registry

+	 *            Item registry where are stored all registered group.

 	 */

-	public DifferenceGroupRegistryImpl(IItemRegistry<IDifferenceGroupProvider.Descriptor> registry,

-			Preferences preferences, String twoWayPreferenceKey, String threeWayPrefenceKey) {

+	public DifferenceGroupRegistryImpl(DifferenceGroupManager groupManager,

+			IItemRegistry<IDifferenceGroupProvider.Descriptor> registry) {

+		this.groupManager = groupManager;

 		this.registry = registry;

-		this.twoWayPreferenceKey = twoWayPreferenceKey;

-		this.threeWayPrefenceKey = threeWayPrefenceKey;

-		this.preferences = preferences;

-	}

-

-	/**

-	 * Return an ordered list of IItemDescriptor<IDifferenceGroupProvider.Descriptor>.

-	 * 

-	 * @return Ordered list of IItemDescriptor<IDifferenceGroupProvider.Descriptor>.

-	 */

-	private List<IItemDescriptor<IDifferenceGroupProvider.Descriptor>> getOrderedGroupProviderDescriptors(

-			final Comparison comparison) {

-		final List<IItemDescriptor<Descriptor>> items;

-		if (comparison.isThreeWay()) {

-			items = ItemUtil.getOrderedItems(getDefaultThreeWayDescriptors(), registry, threeWayPrefenceKey,

-					preferences);

-		} else {

-			items = ItemUtil.getOrderedItems(getDefaultTwoWayDescriptors(), registry, twoWayPreferenceKey,

-					preferences);

-		}

-		return items;

 	}

 

 	/**

@@ -95,7 +66,8 @@ public class DifferenceGroupRegistryImpl implements IDifferenceGroupProvider.Des
 			Comparison comparison) {

 		if (comparison != null) {

 			List<IDifferenceGroupProvider.Descriptor> providers = newArrayList();

-			List<IItemDescriptor<Descriptor>> groupProviderDescriptors = getOrderedGroupProviderDescriptors(comparison);

+			List<IItemDescriptor<Descriptor>> groupProviderDescriptors = groupManager

+					.getCurrentGroupRanking(comparison.isThreeWay());

 			ListIterator<IItemDescriptor<Descriptor>> groupIterator = groupProviderDescriptors.listIterator();

 			while (groupIterator.hasNext()) {

 				IItemDescriptor<Descriptor> desc = groupIterator.next();

@@ -183,49 +155,4 @@ public class DifferenceGroupRegistryImpl implements IDifferenceGroupProvider.Des
 	public void clear() {

 		registry.clear();

 	}

-

-	/**

-	 * Get an ordered list of default descriptors for a three way comparison.

-	 * 

-	 * @return

-	 */

-	private List<IItemDescriptor<Descriptor>> getDefaultTwoWayDescriptors() {

-		Iterable<IItemDescriptor<Descriptor>> threeWayGroups = Iterables.filter(

-				registry.getItemDescriptors(), new Predicate<IItemDescriptor<Descriptor>>() {

-

-					public boolean apply(IItemDescriptor<Descriptor> descriptor) {

-						if (descriptor == null) {

-							return false;

-						}

-						ComparisonType type = descriptor.getItem().getType();

-						return type == ComparisonType.BOTH || type == ComparisonType.TWO_WAY;

-					}

-				});

-		List<IItemDescriptor<Descriptor>> result = Lists.newArrayList(threeWayGroups);

-		Collections.sort(result, Collections.reverseOrder());

-		return result;

-	}

-

-	/**

-	 * Get an ordered list of default descriptors for a three way comparison.

-	 * 

-	 * @return

-	 */

-	private List<IItemDescriptor<Descriptor>> getDefaultThreeWayDescriptors() {

-		Iterable<IItemDescriptor<Descriptor>> twoWayComparison = Iterables.filter(registry

-				.getItemDescriptors(), new Predicate<IItemDescriptor<Descriptor>>() {

-

-			public boolean apply(IItemDescriptor<Descriptor> descriptor) {

-				if (descriptor == null) {

-					return false;

-				}

-				ComparisonType type = descriptor.getItem().getType();

-				return type == ComparisonType.BOTH || type == ComparisonType.THREE_WAY;

-			}

-		});

-		List<IItemDescriptor<Descriptor>> result = Lists.newArrayList(twoWayComparison);

-		Collections.sort(result, Collections.reverseOrder());

-		return result;

-	}

-

 }