org.eclipse.emf.compare.ide.ui.internal.actions.group.DifferenceGrouper.java Source code

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Here is the source code for org.eclipse.emf.compare.ide.ui.internal.actions.group.DifferenceGrouper.java

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/*******************************************************************************
 * Copyright (c) 2012 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.ide.ui.internal.actions.group;

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.List;

import org.eclipse.emf.compare.Comparison;
import org.eclipse.jface.viewers.TreePath;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.swt.events.DisposeEvent;
import org.eclipse.swt.events.DisposeListener;

/**
 * This class will be used by the EMF Compare UI to group differences together in the structural differences
 * tree viewer.
 * 
 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
 */
public final class DifferenceGrouper {
    /**
     * The currently selected group provider. This is what will compute and give us the groups we need to
     * display.
     */
    private DifferenceGroupProvider provider;

    /** List of all TreeViewers on which this filter is applied. */
    private List<TreeViewer> viewers = Lists.newArrayList();

    /**
     * This will be called internally by the ComparisonNode in order to know how it should group its
     * differences.
     * 
     * @param comparison
     *            The comparison which differences need to be grouped.
     * @return The collection of groups we could retrieve from the currently selected group provider. Empty
     *         {@link Iterable} if we have no group provider set.
     */
    public Iterable<? extends DifferenceGroup> getGroups(final Comparison comparison) {
        if (provider == null) {
            return ImmutableList.of();
        }

        final Iterable<? extends DifferenceGroup> groups = provider.getGroups(comparison);
        final Iterable<? extends DifferenceGroup> filteredGroups = Iterables.filter(groups, new NonEmptyGroup());
        return filteredGroups;
    }

    /**
     * Sets the instance that will provide the groups to be displayed in the structural differences view.
     * 
     * @param provider
     *            The provider that will be use to compute the groups that are to be displayed in the UI.
     */
    public void setProvider(DifferenceGroupProvider provider) {
        if (this.provider != provider) {
            this.provider = provider;
            refreshViewers();
        }
    }

    /**
     * Refreshes the viewers registered with this filter. Will try and conserve the expanded tree paths when
     * possible.
     */
    private void refreshViewers() {
        for (TreeViewer viewer : viewers) {
            final TreePath[] paths = viewer.getExpandedTreePaths();
            viewer.refresh();
            viewer.setExpandedTreePaths(paths);
        }
    }

    /**
     * Install this filter on the given viewer.
     * <p>
     * Note that this will also install a dispose listener on that viewer in order to remove the filter
     * whenever the viewer is disposed.
     * </p>
     * 
     * @param viewer
     *            the viewer on which the filter will be installed
     */
    public void install(final TreeViewer viewer) {
        viewer.getTree().addDisposeListener(new DisposeListener() {
            public void widgetDisposed(DisposeEvent e) {
                uninstall(viewer);
            }
        });
        viewers.add(viewer);
    }

    /**
     * Uninstall this filter from the given viewer.
     * 
     * @param viewer
     *            The viewer from which the filter should be removed.
     */
    public void uninstall(TreeViewer viewer) {
        viewers.remove(viewer);
    }

    /**
     * This predicate will be used to filter the empty groups out of the displayed list.
     * 
     * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
     */
    private static class NonEmptyGroup implements Predicate<DifferenceGroup> {
        /**
         * {@inheritDoc}
         * 
         * @see com.google.common.base.Predicate#apply(java.lang.Object)
         */
        public boolean apply(DifferenceGroup input) {
            return input != null && !Iterables.isEmpty(input.getDifferences());
        }
    }
}