/* * @(#)DragRecognitionSupport.java	1.1 05/05/02 * * Copyright 2005 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */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 * @version 1.1 05/02/05 */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 ((DragRecognitionSupport)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 ((DragRecognitionSupport)getDragRecognitionSupport()).            mouseReleasedImpl(me);    }    /**     * Returns whether or not a drag gesture recognition is ongoing.     */    public static boolean mouseDragged(MouseEvent me, BeforeDrag bd) {        return ((DragRecognitionSupport)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;    }}