/*******************************************************************************
* Copyright (c) 2004, 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.eclipse.ui.presentations;
import org.eclipse.jface.util.Geometry;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.ui.internal.dnd.DragUtil;
/**
* Contains various utility methods for Presentation authors
*
* @since 3.0
*/
public class PresentationUtil {
private static Point anchor;
private final static int HYSTERESIS = 16;
private static int initialMouseButton = 0;
private final static String LISTENER_ID = PresentationUtil.class.getName()
+ ".dragListener"; //$NON-NLS-1$
private static Event dragEvent;
private static Listener currentListener = null;
private static Control dragSource;
private static Listener dragListener = new Listener() {
public void handleEvent(Event event) {
dragEvent = event;
if (dragSource != event.widget) {
dragSource = null;
currentListener = null;
}
}
};
/**
* Returns whether the mouse has moved enough to warrant
* opening a tracker.
*/
private static boolean hasMovedEnough(Event event) {
return Geometry.distanceSquared(DragUtil.getEventLoc(event), anchor) >= HYSTERESIS
* HYSTERESIS;
}
private static Listener moveListener = new Listener() {
public void handleEvent(Event event) {
handleMouseMove(event);
}
};
private static Listener clickListener = new Listener() {
public void handleEvent(Event e) {
handleMouseClick(e);
}
};
private static Listener mouseDownListener = new Listener() {
public void handleEvent(Event event) {
if (event.widget instanceof Control) {
// Remember the button that started the drag so we
// can forward it on the call to the 'externalDragListener'
initialMouseButton = event.button;
dragSource = (Control) event.widget;
currentListener = (Listener) dragSource.getData(LISTENER_ID);
anchor = DragUtil.getEventLoc(event);
if (dragEvent != null && (dragEvent.widget != dragSource)) {
dragEvent = null;
}
}
}
};
private static void handleMouseClick(Event event) {
cancelDrag();
}
private static void handleMouseMove(Event e) {
if (currentListener != null && dragEvent != null && hasMovedEnough(e)) {
if (dragSource != null && !dragSource.isDisposed()
&& dragSource == e.widget) {
Event de = dragEvent;
// cache the current value so we can restore it later
int originalMouseButton = de.button;
// Update the button field so that the drag listener
// can detect whether or not it's a 'right button' drag
de.button = initialMouseButton;
Listener l = currentListener;
cancelDrag();
l.handleEvent(de);
// Restore the event's state so that other listeners see
// the original values
de.button = originalMouseButton;
} else {
cancelDrag();
}
}
}
private static void cancelDrag() {
currentListener = null;
dragEvent = null;
dragSource = null;
initialMouseButton = 0;
}
/**
* Adds a drag listener to the given control. The behavior is very similar
* to control.addListener(SWT.DragDetect, dragListener), however the listener
* attached by this method is less sensitive. The drag event is only fired
* once the user moves the cursor more than HYSTERESIS pixels.
* <p>
* This is useful for registering a listener that will trigger an editor or
* view drag, since an overly sensitive drag listener can cause users to accidentally
* drag views when trying to select a tab.</p>
* <p>
* Currently, only one such drag listener can be registered at a time. </p>
*
* @param control the control containing the drag listener
* @param externalDragListener the drag listener to attach
*/
public static void addDragListener(Control control,
Listener externalDragListener) {
control.addListener(SWT.DragDetect, dragListener);
control.addListener(SWT.MouseUp, clickListener);
control.addListener(SWT.MouseDoubleClick, clickListener);
control.addListener(SWT.MouseDown, mouseDownListener);
control.addListener(SWT.MouseMove, moveListener);
control.setData(LISTENER_ID, externalDragListener);
}
/**
* Removes a drag listener that was previously attached using addDragListener
*
* @param control the control containing the drag listener
* @param externalDragListener the drag listener to remove
*/
public static void removeDragListener(Control control,
Listener externalDragListener) {
control.removeListener(SWT.DragDetect, dragListener);
control.removeListener(SWT.MouseUp, clickListener);
control.removeListener(SWT.MouseDoubleClick, clickListener);
control.removeListener(SWT.MouseDown, mouseDownListener);
control.removeListener(SWT.MouseMove, moveListener);
control.setData(LISTENER_ID, null);
if (externalDragListener == currentListener) {
cancelDrag();
}
}
}