org.eclipse.gmf.runtime.gef.ui/src/org/eclipse/gmf/runtime/gef/ui/internal/tools/ConnectionBendpointTrackerEx.java

/******************************************************************************
 * Copyright (c) 2007 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.eclipse.gmf.runtime.gef.ui.internal.tools;

import org.eclipse.draw2d.PositionConstants;
import org.eclipse.draw2d.geometry.Dimension;
import org.eclipse.draw2d.geometry.Point;
import org.eclipse.draw2d.geometry.PrecisionPoint;
import org.eclipse.draw2d.geometry.PrecisionRectangle;
import org.eclipse.draw2d.geometry.Rectangle;
import org.eclipse.gef.ConnectionEditPart;
import org.eclipse.gef.SnapToHelper;
import org.eclipse.gef.requests.BendpointRequest;
import org.eclipse.gef.tools.ConnectionBendpointTracker;
import org.eclipse.swt.SWT;

/**
 * A derived ConnectionBendpointTracker that overrides the updateSourceRequest
 * method allowing bendpoints to snap to grid
 * 
 * @author carson_li
 */
public class ConnectionBendpointTrackerEx extends ConnectionBendpointTracker {

	private PrecisionRectangle sourceRectangle;
	private Point originalLocation = null;
	private final int MODIFIER_NO_SNAPPING;

	/**
	 * Constructs a tracker for the given connection and index.
	 * 
	 * @param editpart:
	 *            the connection
	 * @param i:
	 *            the index of the bendpoint
	 */
	public ConnectionBendpointTrackerEx(ConnectionEditPart editpart, int i) {
		super(editpart, i);
		if (SWT.getPlatform().equals("carbon"))//$NON-NLS-1$
			MODIFIER_NO_SNAPPING = SWT.CTRL;
		else
			MODIFIER_NO_SNAPPING = SWT.ALT;
	}

	/*
	 * @see org.eclipse.gef.tools.SimpleDragTracker#updateSourceRequest()
	 */
	protected void updateSourceRequest() {
		BendpointRequest request = (BendpointRequest) getSourceRequest();

		if (originalLocation == null) {
			originalLocation = getStartLocation().getCopy();
		}

		Dimension delta = getDragMoveDelta();

		if (getCurrentInput().isShiftKeyDown()) {
			float ratio = 0;
			if (delta.width != 0)
				ratio = (float) delta.height / (float) delta.width;

			ratio = Math.abs(ratio);
			if (ratio > 0.5 && ratio < 1.5) {
				if (Math.abs(delta.height) > Math.abs(delta.width)) {
					if (delta.height > 0)
						delta.height = Math.abs(delta.width);
					else
						delta.height = -Math.abs(delta.width);
				} else {
					if (delta.width > 0)
						delta.width = Math.abs(delta.height);
					else
						delta.width = -Math.abs(delta.height);
				}
			} else {
				if (Math.abs(delta.width) > Math.abs(delta.height))
					delta.height = 0;
				else
					delta.width = 0;
			}
		}
		Point moveDelta = new Point(delta.width, delta.height);
		SnapToHelper snapToHelper = (SnapToHelper) getConnectionEditPart()
				.getAdapter(SnapToHelper.class);

		Rectangle rect = new Rectangle(originalLocation.x, originalLocation.y,
				1, 1);
		if (sourceRectangle == null) {
			sourceRectangle = new PrecisionRectangle(rect);
		}

		if (snapToHelper != null
				&& !getCurrentInput().isModKeyDown(MODIFIER_NO_SNAPPING)) {
			PrecisionRectangle baseRect = sourceRectangle.getPreciseCopy();
			baseRect.translate(moveDelta);
			PrecisionPoint preciseDelta = new PrecisionPoint(moveDelta);
			snapToHelper.snapPoint(request, PositionConstants.HORIZONTAL
					| PositionConstants.VERTICAL,
					new PrecisionRectangle[] { baseRect }, preciseDelta);
			Point newLocation = originalLocation.getCopy().translate(
					preciseDelta);
			request.setLocation(newLocation);
		} else {
			request.setLocation(getLocation());
		}
	}

	/*
	 * @see org.eclipse.gef.tools.AbstractTool#handleDragStarted()
	 */
	protected boolean handleDragStarted() {
		originalLocation = null;
		sourceRectangle = null;
		return super.handleDragStarted();
	}

}