EDIT

/*******************************************************************************

 * 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

 *     Intershop, Gunnar Wagenknecht - fix for 44288

 *******************************************************************************/

package org.eclipse.gef.editparts;

import org.eclipse.draw2d.PositionConstants;

import org.eclipse.draw2d.Viewport;

import org.eclipse.draw2d.geometry.Insets;

import org.eclipse.draw2d.geometry.Point;

import org.eclipse.draw2d.geometry.Rectangle;

import org.eclipse.gef.AutoexposeHelper;

import org.eclipse.gef.GraphicalEditPart;

/**

 * An implementation of {@link org.eclipse.gef.AutoexposeHelper} that performs

 * autoscrolling of a <code>Viewport</code> figure. This helper is for use with

 * graphical editparts that contain a viewport figure. This helper will search

 * the editpart and find the viewport. Autoscroll will occur when the detect

 * location is inside the viewport's bounds, but near its edge. It will continue

 * for as long as the location continues to meet these criteria. The autoscroll

 * direction is approximated to the nearest orthogonal or diagonal direction

 * (north, northeast, east, etc.).

 * 

 * @author hudsonr

 */

public class ViewportAutoexposeHelper extends ViewportHelper implements

		AutoexposeHelper {

	/** defines the range where autoscroll is active inside a viewer */

	private static final Insets DEFAULT_EXPOSE_THRESHOLD = new Insets(18);

	/** the last time an auto expose was performed */

	private long lastStepTime = 0;

	/** The insets for this helper. */

	private Insets threshold;

	/**

	 * Constructs a new helper on the given GraphicalEditPart. The editpart must

	 * have a <code>Viewport</code> somewhere between its <i>contentsPane</i>

	 * and its <i>figure</i> inclusively.

	 * 

	 * @param owner

	 *            the GraphicalEditPart that owns the Viewport

	 */

	public ViewportAutoexposeHelper(GraphicalEditPart owner) {

		super(owner);

		threshold = DEFAULT_EXPOSE_THRESHOLD;

	}

	/**

	 * Constructs a new helper on the given GraphicalEditPart. The editpart must

	 * have a <code>Viewport</code> somewhere between its <i>contentsPane</i>

	 * and its <i>figure</i> inclusively.

	 * 

	 * @param owner

	 *            the GraphicalEditPart that owns the Viewport

	 * @param threshold

	 *            the Expose Threshold to use when determing whether or not a

	 *            scroll should occur.

	 */

	public ViewportAutoexposeHelper(GraphicalEditPart owner, Insets threshold) {

		super(owner);

		this.threshold = threshold;

	}

	/**

	 * Returns <code>true</code> if the given point is inside the viewport, but

	 * near its edge.

	 * 

	 * @see org.eclipse.gef.AutoexposeHelper#detect(org.eclipse.draw2d.geometry.Point)

	 */

	public boolean detect(Point where) {

		lastStepTime = 0;

		Viewport port = findViewport(owner);

		Rectangle rect = Rectangle.SINGLETON;

		port.getClientArea(rect);

		port.translateToParent(rect);

		port.translateToAbsolute(rect);

		return rect.contains(where) && !rect.crop(threshold).contains(where);

	}

	/**

	 * Returns <code>true</code> if the given point is outside the viewport or

	 * near its edge. Scrolls the viewport by a calculated (time based) amount

	 * in the current direction.

	 * 

	 * todo: investigate if we should allow auto expose when the pointer is

	 * outside the viewport

	 * 

	 * @see org.eclipse.gef.AutoexposeHelper#step(org.eclipse.draw2d.geometry.Point)

	 */

	public boolean step(Point where) {

		Viewport port = findViewport(owner);

		Rectangle rect = Rectangle.SINGLETON;

		port.getClientArea(rect);

		port.translateToParent(rect);

		port.translateToAbsolute(rect);

		if (!rect.contains(where) || rect.crop(threshold).contains(where))

			return false;

		// set scroll offset (speed factor)

		int scrollOffset = 0;

		// calculate time based scroll offset

		if (lastStepTime == 0)

			lastStepTime = System.currentTimeMillis();

		long difference = System.currentTimeMillis() - lastStepTime;

		if (difference > 0) {

			scrollOffset = ((int) difference / 3);

			lastStepTime = System.currentTimeMillis();

		}

		if (scrollOffset == 0)

			return true;

		rect.crop(threshold);

		int region = rect.getPosition(where);

		Point loc = port.getViewLocation();

		if ((region & PositionConstants.SOUTH) != 0)

			loc.y += scrollOffset;

		else if ((region & PositionConstants.NORTH) != 0)

			loc.y -= scrollOffset;

		if ((region & PositionConstants.EAST) != 0)

			loc.x += scrollOffset;

		else if ((region & PositionConstants.WEST) != 0)

			loc.x -= scrollOffset;

		port.setViewLocation(loc);

		return true;

	}

	/**

	 * @see java.lang.Object#toString()

	 */

	public String toString() {

		return "ViewportAutoexposeHelper for: " + owner; //$NON-NLS-1$

	}

}