PanningSelectionTool.java

/*******************************************************************************
 * Copyright (c) 2000, 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.gef.tools;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.graphics.Cursor;

import org.eclipse.draw2d.FigureCanvas;
import org.eclipse.draw2d.geometry.Point;

import org.eclipse.gef.SharedCursors;

/**
 * A subclass of the SelectionTool that allows panning 
 * by holding down the space bar.
 */
public class PanningSelectionTool 
	extends SelectionTool 
{
	
private boolean isSpaceBarDown = false;
private Point viewLocation;

/**
 * The state to indicate that the space bar has been pressed but 
 * no drag has been initiated.
 */
protected static final int PAN = SelectionTool.MAX_STATE << 1;

/**
 * The state to indicate that a pan is in progress.
 */
protected static final int PAN_IN_PROGRESS = PAN << 1;

/** Max state */
protected static final int MAX_STATE = PAN_IN_PROGRESS;

	
/**
 * Returns <code>true</code> if spacebar condition was accepted.
 * @param e the key event
 * @return true if the space bar was the key event.
 */
protected boolean acceptSpaceBar(KeyEvent e) {
	return (e.character == ' ' && (e.stateMask & SWT.MODIFIER_MASK) == 0);
}

/**
 * @see org.eclipse.gef.tools.AbstractTool#getDebugName()
 */
protected String getDebugName() {
	return "Panning Tool";//$NON-NLS-1$
}

/**
 * @see org.eclipse.gef.tools.AbstractTool#getDebugNameForState(int)
 */
protected String getDebugNameForState(int state) {
	if (state == PAN)
		return "Pan Initial";  //$NON-NLS-1$
	else if (state == PAN_IN_PROGRESS)
		return "Pan In Progress";  //$NON-NLS-1$
	return super.getDebugNameForState(state);
}

/**
 * Returns the cursor used under normal conditions.
 * 
 * @see #setDefaultCursor(Cursor)
 * @return the default cursor
 */
protected Cursor getDefaultCursor() {
	if (isInState(PAN | PAN_IN_PROGRESS))
		return SharedCursors.HAND;
	return super.getDefaultCursor();
}

/**
 * @see org.eclipse.gef.tools.SelectionTool#handleButtonDown(int)
 */
protected boolean handleButtonDown(int which) {
	if (which == 1
			&& getCurrentViewer().getControl() instanceof FigureCanvas
			&& stateTransition(PAN, PAN_IN_PROGRESS)) {
		viewLocation = ((FigureCanvas)
				getCurrentViewer().getControl()).getViewport().getViewLocation();
		return true;
	}
	return super.handleButtonDown(which);
}

/**
 * @see org.eclipse.gef.tools.SelectionTool#handleButtonUp(int)
 */
protected boolean handleButtonUp(int which) {
	if (which == 1 && isSpaceBarDown && stateTransition(PAN_IN_PROGRESS, PAN))
		return true;
	else if (which == 1 && stateTransition(PAN_IN_PROGRESS, STATE_INITIAL)) {
		refreshCursor();
		return true;
	}
	
	return super.handleButtonUp(which);
}

/**
 * @see org.eclipse.gef.tools.AbstractTool#handleDrag()
 */
protected boolean handleDrag() {
	if (isInState(PAN_IN_PROGRESS) 
	   && getCurrentViewer().getControl() instanceof FigureCanvas) {
		FigureCanvas canvas = (FigureCanvas)getCurrentViewer().getControl();
		canvas.scrollTo(viewLocation.x - getDragMoveDelta().width, 
				viewLocation.y - getDragMoveDelta().height);
		return true;
	} else {
		return super.handleDrag();
	}
}

/**
 * @see org.eclipse.gef.tools.SelectionTool#handleFocusLost()
 */
protected boolean handleFocusLost() {
	if (isInState(PAN | PAN_IN_PROGRESS)) {
		setState(STATE_INITIAL);
		refreshCursor();
		return true;
	}
	return super.handleFocusLost();
}

/**
 * @see org.eclipse.gef.tools.SelectionTool#handleKeyDown(org.eclipse.swt.events.KeyEvent)
 */
protected boolean handleKeyDown(KeyEvent e) {
	if (acceptSpaceBar(e)) {
		isSpaceBarDown = true;
		if (stateTransition(STATE_INITIAL, PAN))
			refreshCursor();
		return true;
	} else {
		if (stateTransition(PAN, STATE_INITIAL)) {
			refreshCursor();
			isSpaceBarDown = false;
			return true;
		} else if (isInState(PAN_IN_PROGRESS)) 
			isSpaceBarDown = false;
	}
	
	return super.handleKeyDown(e);
}

/**
 * @see org.eclipse.gef.tools.SelectionTool#handleKeyUp(org.eclipse.swt.events.KeyEvent)
 */
protected boolean handleKeyUp(KeyEvent e) {
	if (acceptSpaceBar(e)) {
		isSpaceBarDown = false;
		if (stateTransition(PAN, STATE_INITIAL))
			refreshCursor();
		return true;
	}

	return super.handleKeyUp(e);
}

}