/* * Copyright (c) 2005, 2008, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */package javax.swing.plaf.basic; import java.awt.Toolkit;import java.awt.event.*;import java.awt.dnd.DragSource;import javax.swing.*;import sun.awt.dnd.SunDragSourceContextPeer;import sun.awt.AppContext; /** * Drag gesture recognition support for classes that have a * <code>TransferHandler</code>. The gesture for a drag in this class is a mouse * press followed by movement by <code>DragSource.getDragThreshold()</code> * pixels. An instance of this class is maintained per AppContext, and the * public static methods call into the appropriate instance. * * @author Shannon Hickey */class DragRecognitionSupport {    private int motionThreshold;    private MouseEvent dndArmedEvent;    private JComponent component;     /**     * This interface allows us to pass in a handler to mouseDragged,     * so that we can be notified immediately before a drag begins.     */    public static interface BeforeDrag {        public void dragStarting(MouseEvent me);    }     /**     * Returns the DragRecognitionSupport for the caller's AppContext.     */    private static DragRecognitionSupport getDragRecognitionSupport() {        DragRecognitionSupport support =            (DragRecognitionSupport)AppContext.getAppContext().                get(DragRecognitionSupport.class);         if (support == null) {            support = new DragRecognitionSupport();            AppContext.getAppContext().put(DragRecognitionSupport.class, support);        }         return support;    }     /**     * Returns whether or not the event is potentially part of a drag sequence.     */    public static boolean mousePressed(MouseEvent me) {        return getDragRecognitionSupport().mousePressedImpl(me);    }     /**     * If a dnd recognition has been going on, return the MouseEvent     * that started the recognition. Otherwise, return null.     */    public static MouseEvent mouseReleased(MouseEvent me) {        return getDragRecognitionSupport().mouseReleasedImpl(me);    }     /**     * Returns whether or not a drag gesture recognition is ongoing.     */    public static boolean mouseDragged(MouseEvent me, BeforeDrag bd) {        return getDragRecognitionSupport().mouseDraggedImpl(me, bd);    }     private void clearState() {        dndArmedEvent = null;        component = null;    }     private int mapDragOperationFromModifiers(MouseEvent me,                                              TransferHandler th) {         if (th == null || !SwingUtilities.isLeftMouseButton(me)) {            return TransferHandler.NONE;        }         return SunDragSourceContextPeer.            convertModifiersToDropAction(me.getModifiersEx(),                                         th.getSourceActions(component));    }     /**     * Returns whether or not the event is potentially part of a drag sequence.     */    private boolean mousePressedImpl(MouseEvent me) {        component = (JComponent)me.getSource();         if (mapDragOperationFromModifiers(me, component.getTransferHandler())                != TransferHandler.NONE) {             motionThreshold = DragSource.getDragThreshold();            dndArmedEvent = me;            return true;        }         clearState();        return false;    }     /**     * If a dnd recognition has been going on, return the MouseEvent     * that started the recognition. Otherwise, return null.     */    private MouseEvent mouseReleasedImpl(MouseEvent me) {        /* no recognition has been going on */        if (dndArmedEvent == null) {            return null;        }         MouseEvent retEvent = null;         if (me.getSource() == component) {            retEvent = dndArmedEvent;        } // else component has changed unexpectedly, so return null         clearState();        return retEvent;    }     /**     * Returns whether or not a drag gesture recognition is ongoing.     */    private boolean mouseDraggedImpl(MouseEvent me, BeforeDrag bd) {        /* no recognition is in progress */        if (dndArmedEvent == null) {            return false;        }         /* component has changed unexpectedly, so bail */        if (me.getSource() != component) {            clearState();            return false;        }         int dx = Math.abs(me.getX() - dndArmedEvent.getX());        int dy = Math.abs(me.getY() - dndArmedEvent.getY());        if ((dx > motionThreshold) || (dy > motionThreshold)) {            TransferHandler th = component.getTransferHandler();            int action = mapDragOperationFromModifiers(me, th);            if (action != TransferHandler.NONE) {                /* notify the BeforeDrag instance */                if (bd != null) {                    bd.dragStarting(dndArmedEvent);                }                th.exportAsDrag(component, dndArmedEvent, action);                clearState();            }        }         return true;    }}