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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 TransferHandler. The gesture for a drag in this class is a mouse press followed by movement by DragSource.getDragThreshold() pixels. An instance of this class is maintained per AppContext, and the public static methods call into the appropriate instance.
Author:Shannon Hickey
/** * 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.
/** * 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.
/** * 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.
/** * 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.
/** * 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.
/** * 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.
/** * 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.
/** * 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.
/** * 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; } }