at.bitandart.zoubek.mervin.util.vis.ThreeWayTreeViewerComparator.java Source code

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/*******************************************************************************
 * Copyright (c) 2015, 2016 Florian Zoubek.
 * 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:
 *    Florian Zoubek - initial API and implementation
 *******************************************************************************/
package at.bitandart.zoubek.mervin.util.vis;

import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.jface.viewers.TreeViewerColumn;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.jface.viewers.ViewerComparator;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.widgets.Tree;
import org.eclipse.swt.widgets.TreeColumn;

/**
 * A {@link ViewerComparator} and {@link SelectionListener} that can be applied
 * to {@link TreeColumn}s to provide the default three way (none, ascending,
 * descending) sorting behavior based on default {@link ViewerComparator}
 * implementation.
 * 
 * @author Florian Zoubek
 *
 */
public class ThreeWayTreeViewerComparator extends ViewerComparator implements SelectionListener {

    private TreeViewer viewer;
    private TreeViewerColumn treeColumn;

    private int sortDirection = SWT.NONE;

    public ThreeWayTreeViewerComparator(TreeViewer viewer, TreeViewerColumn treeColumn) {
        this.viewer = viewer;
        this.treeColumn = treeColumn;
    }

    @Override
    public int compare(Viewer viewer, Object e1, Object e2) {
        return super.compare(viewer, e1, e2) * getDirectionFactor();
    }

    @Override
    public void widgetSelected(SelectionEvent e) {
        Tree tree = viewer.getTree();
        switch (sortDirection) {
        case SWT.UP:
            sortDirection = SWT.DOWN;
            break;
        case SWT.DOWN:
            sortDirection = SWT.NONE;
            break;
        default:
        case SWT.NONE:
            sortDirection = SWT.UP;
            break;
        }
        tree.setSortDirection(sortDirection);
        viewer.setComparator(this);
        tree.setSortColumn(treeColumn.getColumn());
        viewer.refresh();

    }

    @Override
    public void widgetDefaultSelected(SelectionEvent e) {
    }

    /**
     * @return the factor that can be used to turn the default comparison result
     *         in the correct sorting direction.
     */
    protected int getDirectionFactor() {
        switch (sortDirection) {
        case SWT.UP:
            return 1;
        case SWT.DOWN:
            return -1;
        default:
        case SWT.NONE:
            return 0;
        }
    }

    public TreeViewer getViewer() {
        return viewer;
    }

    public TreeViewerColumn getTreeColumn() {
        return treeColumn;
    }
}