EDIT

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

 * Copyright (c) 2003, 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

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

package org.eclipse.gef.editpolicies;

import org.eclipse.swt.graphics.Color;

import org.eclipse.swt.graphics.Image;

import org.eclipse.swt.graphics.ImageData;

import org.eclipse.swt.graphics.PaletteData;

import org.eclipse.swt.widgets.Display;

import org.eclipse.draw2d.ColorConstants;

import org.eclipse.draw2d.Figure;

import org.eclipse.draw2d.FigureUtilities;

import org.eclipse.draw2d.Graphics;

import org.eclipse.draw2d.IFigure;

import org.eclipse.draw2d.geometry.PrecisionPoint;

import org.eclipse.draw2d.geometry.Rectangle;

import org.eclipse.gef.GraphicalEditPart;

import org.eclipse.gef.Request;

import org.eclipse.gef.SnapToGeometry;

import org.eclipse.gef.SnapToGuides;

/**

 * An EditPolicy that is used to show snap feedback for guides (red lines) and

 * geometry (blue lines). This policy is not required for Grids.

 * 

 * @author Randy Hudson

 * @author Pratik Shah

 * @since 3.0

 */

public class SnapFeedbackPolicy extends GraphicalEditPolicy {

	IFigure guide[] = new IFigure[6];

	Integer location[] = new Integer[6];

	/**

	 * @see org.eclipse.gef.EditPolicy#eraseTargetFeedback(org.eclipse.gef.Request)

	 */

	public void eraseTargetFeedback(Request request) {

		for (int i = 0; i < guide.length; i++) {

			if (guide[i] != null)

				removeFeedback(guide[i]);

			guide[i] = null;

			location[i] = null;

		}

	}

	static class FadeIn extends Figure {

		int opacity = 0;

		static final int FRAMES = 6;

		Image image;

		static int count;

		FadeIn(Color bg) {

			setBackgroundColor(bg);

			super.setOpaque(true);

		}

		private Color createMixedColor() {

			return FigureUtilities

					.mixColors(getLocalBackgroundColor(), getParent()

							.getBackgroundColor(), (double) opacity / FRAMES);

		}

		/**

		 * @see org.eclipse.draw2d.Figure#paintFigure(org.eclipse.draw2d.Graphics)

		 */

		protected void paintFigure(Graphics graphics) {

			if (opacity != FRAMES) {

				if (image != null) {

					image.dispose();

					count--;

					image = null;

				}

				if (opacity != FRAMES - 1) {

					Display display = Display.getCurrent();

					PaletteData pData = new PaletteData(0xFF, 0xFF00, 0xFF0000);

					Color localBackgroundColor = createMixedColor();

					int fillColor = pData.getPixel(localBackgroundColor

							.getRGB());

					localBackgroundColor.dispose();

					ImageData iData = new ImageData(1, 1, 24, pData);

					iData.setPixel(0, 0, fillColor);

					iData.setAlpha(0, 0, 255 * opacity / FRAMES);

					image = new Image(display, iData);

					count++;

				}

				Display.getCurrent().timerExec(100, new Runnable() {

					public void run() {

						opacity = Math.min(FRAMES, opacity + 1);

						repaint();

					}

				});

			}

			Rectangle r = getBounds();

			if (image != null)

				graphics.drawImage(image, 0, 0, 1, 1, r.x, r.y, r.width,

						r.height);

			else

				super.paintFigure(graphics);

		}

		/**

		 * @see org.eclipse.draw2d.Figure#removeNotify()

		 */

		public void removeNotify() {

			if (image != null) {

				image.dispose();

				count--;

				image = null;

			}

		}

	}

	// Even offset indicates a vertical feedback line; odd, horizontal.

	void highlightGuide(Integer pos, Color color, int offset) {

		if (pos == null) {

			if (guide[offset] != null) {

				removeFeedback(guide[offset]);

				guide[offset] = null;

			}

			location[offset] = pos;

			return;

		}

		// pos is an integer relative to target's client area.

		// translate pos to absolute, and then make it relative to fig.

		int position = pos.intValue();

		PrecisionPoint loc = new PrecisionPoint(position, position);

		IFigure contentPane = ((GraphicalEditPart) getHost()).getContentPane();

		contentPane.translateToParent(loc);

		contentPane.translateToAbsolute(loc);

		if (location[offset] == null || !location[offset].equals(pos)) {

			location[offset] = pos;

			if (guide[offset] != null) {

				removeFeedback(guide[offset]);

				guide[offset] = null;

			}

			IFigure fig = new FadeIn(color);

			guide[offset] = fig;

			addFeedback(fig);

			fig.translateToRelative(loc);

			position = offset % 2 == 0 ? (int) Math.round(loc.preciseX())

					: (int) Math.round(loc.preciseY());

			Rectangle figBounds = getFeedbackLayer().getBounds().getCopy();

			if ((offset % 2) == 1) {

				figBounds.height = 1;

				figBounds.y = position;

			} else {

				figBounds.x = position;

				figBounds.width = 1;

			}

			fig.setBounds(figBounds);

		} else {

			// The feedback layer could have grown (if auto-scrolling), so

			// resize the fade-in

			// line.

			IFigure fig = guide[offset];

			Rectangle figBounds = fig.getBounds().getCopy();

			Rectangle feedbackBounds = getFeedbackLayer().getBounds();

			if ((offset % 2) == 1) {

				figBounds.x = feedbackBounds.x;

				figBounds.width = feedbackBounds.width;

			} else {

				figBounds.y = feedbackBounds.y;

				figBounds.height = feedbackBounds.height;

			}

			fig.setBounds(figBounds);

		}

	}

	/**

	 * @see org.eclipse.gef.EditPolicy#showTargetFeedback(org.eclipse.gef.Request)

	 */

	public void showTargetFeedback(Request req) {

		if (req.getType().equals(REQ_MOVE) || req.getType().equals(REQ_RESIZE)

				|| req.getType().equals(REQ_CLONE)

				|| req.getType().equals(REQ_ADD)

				|| req.getType().equals(REQ_CREATE)) {

			Integer value;

			value = (Integer) req.getExtendedData().get(

					SnapToGeometry.KEY_WEST_ANCHOR);

			highlightGuide(value, ColorConstants.blue, 0);

			value = (Integer) req.getExtendedData().get(

					SnapToGeometry.KEY_NORTH_ANCHOR);

			highlightGuide(value, ColorConstants.blue, 1);

			value = (Integer) req.getExtendedData().get(

					SnapToGeometry.KEY_EAST_ANCHOR);

			highlightGuide(value, ColorConstants.blue, 2);

			value = (Integer) req.getExtendedData().get(

					SnapToGeometry.KEY_SOUTH_ANCHOR);

			highlightGuide(value, ColorConstants.blue, 3);

			value = (Integer) req.getExtendedData().get(

					SnapToGuides.KEY_VERTICAL_GUIDE);

			highlightGuide(value, ColorConstants.red, 4);

			value = (Integer) req.getExtendedData().get(

					SnapToGuides.KEY_HORIZONTAL_GUIDE);

			highlightGuide(value, ColorConstants.red, 5);

		}

	}

}