dragsourcedragevent.java

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/*
 * @(#)DragSourceDragEvent.java	1.26 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.awt.dnd;

import java.awt.event.InputEvent;

/**
 * The <code>DragSourceDragEvent</code> is 
 * delivered from the <code>DragSourceContextPeer</code>,
 * via the <code>DragSourceContext</code>, to the <code>DragSourceListener</code> 
 * registered with that <code>DragSourceContext</code> and with its associated
 * <code>DragSource</code>. 
 * <p>
 * The <code>DragSourceDragEvent</code> reports the <i>target drop action</i>
 * and the <i>user drop action</i> that reflect the current state of 
 * the drag operation.
 * <p>
 * <i>Target drop action</i> is one of <code>DnDConstants</code> that represents
 * the drop action selected by the current drop target if this drop action is
 * supported by the drag source or <code>DnDConstants.ACTION_NONE</code> if this
 * drop action is not supported by the drag source.
 * <p>
 * <i>User drop action</i> depends on the drop actions supported by the drag
 * source and the drop action selected by the user. The user can select a drop
 * action by pressing modifier keys during the drag operation: 
 * <pre> 
 *   Ctrl + Shift -> ACTION_LINK
 *   Ctrl         -> ACTION_COPY
 *   Shift        -> ACTION_MOVE
 * </pre> 
 * If the user selects a drop action, the <i>user drop action</i> is one of 
 * <code>DnDConstants</code> that represents the selected drop action if this
 * drop action is supported by the drag source or
 * <code>DnDConstants.ACTION_NONE</code> if this drop action is not supported 
 * by the drag source.
 * <p>
 * If the user doesn't select a drop action, the set of
 * <code>DnDConstants</code> that represents the set of drop actions supported
 * by the drag source is searched for <code>DnDConstants.ACTION_MOVE</code>,
 * then for <code>DnDConstants.ACTION_COPY</code>, then for
 * <code>DnDConstants.ACTION_LINK</code> and the <i>user drop action</i> is the
 * first constant found. If no constant is found the <i>user drop action</i>
 * is <code>DnDConstants.ACTION_NONE</code>.
 *
 * @version 	1.26, 01/23/03
 * @since 1.2
 *
 */

public class DragSourceDragEvent extends DragSourceEvent {

    private static final long serialVersionUID = 481346297933902471L;

    /**
     * Constructs a <code>DragSourceDragEvent</code>. 
     * This class is typically 
     * instantiated by the <code>DragSourceContextPeer</code> 
     * rather than directly 
     * by client code.
     * The coordinates for this <code>DragSourceDragEvent</code>  
     * are not specified, so <code>getLocation</code> will return
     * <code>null</code> for this event.
     * 
     * @param dsc the <code>DragSourceContext</code> that is to manage 
     *            notifications for this event.
     * @param dropAction the user drop action.
     * @param actions the target drop action.
     * @param modifiers the modifier keys down during event (shift, ctrl,
     *        alt, meta)
     *        Either extended _DOWN_MASK or old _MASK modifiers
     *        should be used, but both models should not be mixed
     *        in one event. Use of the extended modifiers is
     *        preferred.
     * @see java.awt.event.InputEvent
     * @see DragSourceEvent#getLocation
     */

    public DragSourceDragEvent(DragSourceContext dsc, int dropAction, 
                               int actions, int modifiers) { 
	super(dsc);
	
	targetActions    = actions;
	gestureModifiers = modifiers;
	this.dropAction  = dropAction;
    }

    /**
     * Constructs a <code>DragSourceDragEvent</code> given the specified
     * <code>DragSourceContext</code>, user drop action, target drop action,
     * modifiers and coordinates.
     * 
     * @param dsc the <code>DragSourceContext</code> associated with this
     *        event. 
     * @param dropAction the user drop action.
     * @param actions the target drop action.
     * @param modifiers the modifier keys down during event (shift, ctrl,
     *        alt, meta)
     *        Either extended _DOWN_MASK or old _MASK modifiers
     *        should be used, but both models should not be mixed
     *        in one event. Use of the extended modifiers is
     *        preferred.
     * @param x   the horizontal coordinate for the cursor location
     * @param y   the vertical coordinate for the cursor location
     * @see java.awt.event.InputEvent
     * @since 1.4
     */
    public DragSourceDragEvent(DragSourceContext dsc, int dropAction, 
                               int actions, int modifiers, int x, int y) {
        super(dsc, x, y);

        targetActions    = actions;
        gestureModifiers = modifiers;
        this.dropAction  = dropAction;
        if ((getGestureModifiers() != 0) && (getGestureModifiersEx() == 0)) {
	    setNewModifiers();    
	} else if ((getGestureModifiers() == 0) && (getGestureModifiersEx() != 0)) {
	    setOldModifiers();
	}
    }

    /**
     * This method returns the target drop action.
     *
     * @return the target drop action.
     */
    public int getTargetActions() {
	return targetActions;
    }


    static final int JDK_1_3_MODIFIERS = InputEvent.SHIFT_DOWN_MASK - 1;

    /**
     * This method returns an <code>int</code> representing
     * the current state of the input device modifiers
     * associated with the user's gesture. Typically these
     * would be mouse buttons or keyboard modifiers.
     * <P>
     * @return the current state of the input device modifiers
     */

    public int getGestureModifiers() {
	return gestureModifiers & JDK_1_3_MODIFIERS;
    }

    /**
     * This method returns an <code>int</code> representing
     * the current state of the input device extended modifiers
     * associated with the user's gesture. 
     * See {@link InputEvent#getModifiersEx}
     * <P>
     * @return the current state of the input device extended modifiers
     * @since 1.4
     */

    public int getGestureModifiersEx() {
	return gestureModifiers & ~JDK_1_3_MODIFIERS;
    }

    /**
     * This method returns the user drop action.
     * 
     * @return the user drop action.
     */
    public int getUserAction() { return dropAction; }

    /**
     * This method returns the logical intersection of the user drop action, 
     * the target drop action and the set of drop actions supported by 
     * the drag source.
     *
     * @return the logical intersection of the user drop action, the target drop
     *         action and the set of drop actions supported by the drag source.
     */
    public int getDropAction() {
	return dropAction & targetActions & getDragSourceContext().getSourceActions();
    }

    /*
     * fields
     */

    /**
     * The target drop action.
     *
     * @serial
     */
    private int	    targetActions    = DnDConstants.ACTION_NONE;

    /**
     * The user drop action.
     *
     * @serial
     */
    private int	    dropAction       = DnDConstants.ACTION_NONE;

    /**
     * The state of the input device modifiers associated with the user
     * gesture.
     *
     * @serial
     */
    private int	    gestureModifiers = 0;

    /**
     * Sets new modifiers by the old ones. 
     * The mouse modifiers have higher priority than overlaying key 
     * modifiers.
     */
    private void setNewModifiers() {
    	if ((gestureModifiers & InputEvent.BUTTON1_MASK) != 0) {
	    gestureModifiers |= InputEvent.BUTTON1_DOWN_MASK;
	}
	if ((gestureModifiers & InputEvent.BUTTON2_MASK) != 0) {
	    gestureModifiers |= InputEvent.BUTTON2_DOWN_MASK;
	}
	if ((gestureModifiers & InputEvent.BUTTON3_MASK) != 0) {
	    gestureModifiers |= InputEvent.BUTTON3_DOWN_MASK;
	}	
	if ((gestureModifiers & InputEvent.SHIFT_MASK) != 0) {
	    gestureModifiers |= InputEvent.SHIFT_DOWN_MASK;
	}
	if ((gestureModifiers & InputEvent.CTRL_MASK) != 0) {
	    gestureModifiers |= InputEvent.CTRL_DOWN_MASK;
	}
	if ((gestureModifiers & InputEvent.ALT_GRAPH_MASK) != 0) {
	    gestureModifiers |= InputEvent.ALT_GRAPH_DOWN_MASK;
	}
    }	

    /**
     * Sets old modifiers by the new ones. 
     */
    private void setOldModifiers() {
	if ((gestureModifiers & InputEvent.BUTTON1_DOWN_MASK) != 0) {
	    gestureModifiers |= InputEvent.BUTTON1_MASK;
        }
        if ((gestureModifiers & InputEvent.BUTTON2_DOWN_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON2_MASK;
        }
	if ((gestureModifiers & InputEvent.BUTTON3_DOWN_MASK) != 0) {
	    gestureModifiers |= InputEvent.BUTTON3_MASK;
        }
	if ((gestureModifiers & InputEvent.SHIFT_DOWN_MASK) != 0) {
	    gestureModifiers |= InputEvent.SHIFT_MASK;
	}
	if ((gestureModifiers & InputEvent.CTRL_DOWN_MASK) != 0) {
	    gestureModifiers |= InputEvent.CTRL_MASK;
	}
	if ((gestureModifiers & InputEvent.ALT_GRAPH_DOWN_MASK) != 0) {
	    gestureModifiers |= InputEvent.ALT_GRAPH_MASK;
	}
    }
}