/*******************************************************************************
 * Copyright (c) 2006 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.erlide.ui.editors.erl.outline;

import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.swt.events.MouseEvent;
import org.eclipse.swt.events.MouseMoveListener;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.widgets.Item;
import org.eclipse.swt.widgets.Tree;
import org.eclipse.swt.widgets.TreeItem;

/**
 * QuickOutlineMouseMoveListener
 *
 */
public class QuickOutlineMouseMoveListener implements MouseMoveListener {

    private TreeItem fLastItem;

    private final TreeViewer fTreeViewer;

    /**
     *
     */
    public QuickOutlineMouseMoveListener(final TreeViewer treeViewer) {
        fLastItem = null;
        fTreeViewer = treeViewer;
    }

    @Override
    public void mouseMove(final MouseEvent e) {
        final Tree tree = fTreeViewer.getTree();
        if (tree.equals(e.getSource())) {
            final Object o = tree.getItem(new Point(e.x, e.y));
            if (o != null && !o.equals(fLastItem)) {
                fLastItem = (TreeItem) o;
                tree.setSelection(new TreeItem[] { fLastItem });
            } else if (e.y < tree.getItemHeight() / 4) {
                // Scroll up
                final Point p = tree.toDisplay(e.x, e.y);
                final Item item = fTreeViewer.scrollUp(p.x, p.y);
                if (item instanceof TreeItem) {
                    fLastItem = (TreeItem) item;
                    tree.setSelection(new TreeItem[] { fLastItem });
                }
            } else if (e.y > tree.getBounds().height - tree.getItemHeight() / 4) {
                // Scroll down
                final Point p = tree.toDisplay(e.x, e.y);
                final Item item = fTreeViewer.scrollDown(p.x, p.y);
                if (item instanceof TreeItem) {
                    fLastItem = (TreeItem) item;
                    tree.setSelection(new TreeItem[] { fLastItem });
                }
            }
        }
    }

}