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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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.
 *
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package com.sun.javafx.embed.swing;

import com.sun.javafx.embed.EmbeddedSceneDSInterface;
import com.sun.javafx.embed.EmbeddedSceneDTInterface;
import com.sun.javafx.embed.EmbeddedSceneInterface;
import com.sun.javafx.embed.HostDragStartListener;
import com.sun.javafx.tk.Toolkit;
import java.awt.Point;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureRecognizer;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceAdapter;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceListener;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetAdapter;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.DropTargetListener;
import java.awt.dnd.InvalidDnDOperationException;
import java.awt.event.InputEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.EnumSet;
import java.util.List;
import java.util.Set;
import javafx.scene.input.TransferMode;
import javax.swing.JComponent;
import javax.swing.SwingUtilities;

/**
 * An utility class to connect DnD mechanism of Swing and FX.
 * It allows FX content to use the AWT machinery for performing DnD.
 */
final public class SwingDnD {

    private final Transferable dndTransferable = new DnDTransferable();

    private final DragSource dragSource;
    private final DragSourceListener dragSourceListener;

    // swingDragSource and fxDropTarget are used when DnD is initiated from
    // Swing or external process, i.e. this SwingDnD is used as a drop target
    private SwingDragSource swingDragSource;
    private EmbeddedSceneDTInterface fxDropTarget;

    // fxDragSource is used when DnD is initiated from FX, i.e. this
    // SwingDnD acts as a drag source
    private EmbeddedSceneDSInterface fxDragSource;

    private MouseEvent me;

    public SwingDnD(final JComponent comp, final EmbeddedSceneInterface embeddedScene) {

        comp.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent me) {
                storeMouseEvent(me);
            }
            @Override
            public void mouseDragged(MouseEvent me) {
                storeMouseEvent(me);
            }
            @Override
            public void mousePressed(MouseEvent me) {
                storeMouseEvent(me);
            }
            @Override
            public void mouseReleased(MouseEvent me) {
                storeMouseEvent(me);
            }
        });

        dragSource = new DragSource();
        dragSourceListener = new DragSourceAdapter() {
            @Override
            public void dragDropEnd(final DragSourceDropEvent dsde) {
                assert fxDragSource != null;
                try {
                    fxDragSource.dragDropEnd(dropActionToTransferMode(dsde.getDropAction()));
                } finally {
                    fxDragSource = null;
                }
            }
        };

        DropTargetListener dtl = new DropTargetAdapter() {
            private TransferMode lastTransferMode;

            @Override
            public void dragEnter(final DropTargetDragEvent e) {
                // This is a temporary workaround for JDK-8027913
                if ((swingDragSource != null) || (fxDropTarget != null)) {
                    return;
                }

                assert swingDragSource == null;
                swingDragSource = new SwingDragSource();
                swingDragSource.updateContents(e, false);

                assert fxDropTarget == null;
                // Cache the Transferable data in advance, as it cannot be
                // queried from drop(). See comments in dragOver() and in
                // drop() below
                fxDropTarget = embeddedScene.createDropTarget();

                final Point orig = e.getLocation();
                final Point screen = new Point(orig);
                SwingUtilities.convertPointToScreen(screen, comp);
                lastTransferMode = fxDropTarget.handleDragEnter(
                        orig.x, orig.y, screen.x, screen.y,
                        dropActionToTransferMode(e.getDropAction()), swingDragSource);
                applyDragResult(lastTransferMode, e);
            }

            @Override
            public void dragExit(final DropTargetEvent e) {
                assert swingDragSource != null;
                assert fxDropTarget != null;
                try {
                    fxDropTarget.handleDragLeave();
                } finally {
                    endDnD();
                    lastTransferMode = null;
                }
            }

            @Override
            public void dragOver(final DropTargetDragEvent e) {
                assert swingDragSource != null;
                swingDragSource.updateContents(e, false);

                assert fxDropTarget != null;
                final Point orig = e.getLocation();
                final Point screen = new Point(orig);
                SwingUtilities.convertPointToScreen(screen, comp);
                lastTransferMode = fxDropTarget.handleDragOver(
                        orig.x, orig.y, screen.x, screen.y,
                        dropActionToTransferMode(e.getDropAction()));
                applyDragResult(lastTransferMode, e);
            }

            @Override
            public void drop(final DropTargetDropEvent e) {
                assert swingDragSource != null;

                // This allows the subsequent call to updateContents() to
                // actually fetch the data from a drag source. The actual
                // and final drop result may be redefined later.
                applyDropResult(lastTransferMode, e);
                swingDragSource.updateContents(e, true);

                final Point orig = e.getLocation();
                final Point screen = new Point(orig);
                SwingUtilities.convertPointToScreen(screen, comp);

                assert fxDropTarget != null;
                try {
                    lastTransferMode = fxDropTarget.handleDragDrop(
                            orig.x, orig.y, screen.x, screen.y,
                            dropActionToTransferMode(e.getDropAction()));
                    try {
                        applyDropResult(lastTransferMode, e);
                    } catch (InvalidDnDOperationException ignore) {
                        // This means the JDK doesn't contain a fix for 8029979 yet.
                        // DnD still works, but a drag source won't know about
                        // the actual drop result reported by the FX app from
                        // its drop() handler. It will use the dropResult from
                        // the last call to dragOver() instead.
                    }
                } finally {
                    e.dropComplete(lastTransferMode != null);
                    endDnD();
                    lastTransferMode = null;
                }
            }
        };
        comp.setDropTarget(new DropTarget(comp,
                DnDConstants.ACTION_COPY | DnDConstants.ACTION_MOVE | DnDConstants.ACTION_LINK, dtl));

    }

    public void addNotify() {
        dragSource.addDragSourceListener(dragSourceListener);
    }

    public void removeNotify() {
        // RT-22049: Multi-JFrame/JFXPanel app leaks JFXPanels
        // Don't forget to unregister drag source listener!
        dragSource.removeDragSourceListener(dragSourceListener);
    }

    public HostDragStartListener getDragStartListener() {
        return (dragSource, dragAction) -> {
            assert Toolkit.getToolkit().isFxUserThread();
            assert dragSource != null;

            // The method is called from FX Scene just before entering
            // nested event loop servicing DnD events.
            // It should initialize DnD in AWT EDT.
            SwingUtilities.invokeLater(() -> {
                assert fxDragSource == null;
                assert swingDragSource == null;
                assert fxDropTarget == null;

                fxDragSource = dragSource;
                startDrag(me, dndTransferable, dragSource.
                        getSupportedActions(), dragAction);
            });
        };
    }

    private void startDrag(final MouseEvent e, final Transferable t,
                                  final Set<TransferMode> sa,
                                  final TransferMode dragAction)
    {
        assert sa.contains(dragAction);
        // This is a replacement for the default AWT drag gesture recognizer.
        // Not sure DragGestureRecognizer was ever supposed to be used this way.
        final class StubDragGestureRecognizer extends DragGestureRecognizer {
            StubDragGestureRecognizer(DragSource ds) {
                super(ds, e.getComponent());
                setSourceActions(transferModesToDropActions(sa));
                appendEvent(e);
            }
            @Override
            protected void registerListeners() {
            }
            @Override
            protected void unregisterListeners() {
            }
        }

        final Point pt = new Point(e.getX(), e.getY());
        final int action = transferModeToDropAction(dragAction);
        final DragGestureRecognizer dgs = new StubDragGestureRecognizer(dragSource);
        final List<InputEvent> events =
                Arrays.asList(new InputEvent[] { dgs.getTriggerEvent() });
        final DragGestureEvent dse = new DragGestureEvent(dgs, action, pt, events);
        dse.startDrag(null, t);
    }

    private void endDnD() {
        assert swingDragSource != null;
        assert fxDropTarget != null;
        fxDropTarget = null;
        swingDragSource = null;
    }

    private void storeMouseEvent(final MouseEvent me) {
        this.me = me;
    }

    private void applyDragResult(final TransferMode dragResult,
                                 final DropTargetDragEvent e)
    {
        if (dragResult == null) {
            e.rejectDrag();
        } else {
            e.acceptDrag(transferModeToDropAction(dragResult));
        }
    }

    private void applyDropResult(final TransferMode dropResult,
                                 final DropTargetDropEvent e)
    {
        if (dropResult == null) {
            e.rejectDrop();
        } else {
            e.acceptDrop(transferModeToDropAction(dropResult));
        }
    }

    public static TransferMode dropActionToTransferMode(final int dropAction) {
        switch (dropAction) {
            case DnDConstants.ACTION_COPY:
                return TransferMode.COPY;
            case DnDConstants.ACTION_MOVE:
                return TransferMode.MOVE;
            case DnDConstants.ACTION_LINK:
                return TransferMode.LINK;
            case DnDConstants.ACTION_NONE:
                return null;
            default:
                throw new IllegalArgumentException();
        }
    }

    public static int transferModeToDropAction(final TransferMode tm) {
        switch (tm) {
            case COPY:
                return DnDConstants.ACTION_COPY;
            case MOVE:
                return DnDConstants.ACTION_MOVE;
            case LINK:
                return DnDConstants.ACTION_LINK;
            default:
                throw new IllegalArgumentException();
        }
    }

    public static Set<TransferMode> dropActionsToTransferModes(
            final int dropActions)
    {
        final Set<TransferMode> tms = EnumSet.noneOf(TransferMode.class);
        if ((dropActions & DnDConstants.ACTION_COPY) != 0) {
            tms.add(TransferMode.COPY);
        }
        if ((dropActions & DnDConstants.ACTION_MOVE) != 0) {
            tms.add(TransferMode.MOVE);
        }
        if ((dropActions & DnDConstants.ACTION_LINK) != 0) {
            tms.add(TransferMode.LINK);
        }
        return Collections.unmodifiableSet(tms);
    }

    public static int transferModesToDropActions(final Set<TransferMode> tms) {
        int dropActions = DnDConstants.ACTION_NONE;
        for (TransferMode tm : tms) {
            dropActions |= transferModeToDropAction(tm);
        }
        return dropActions;
    }

    // Transferable wrapper over FX dragboard. All the calls are
    // forwarded to FX and executed on the FX event thread.
    private final class DnDTransferable implements Transferable {

        @Override
        public Object getTransferData(final DataFlavor flavor)
                throws UnsupportedEncodingException
        {
            assert fxDragSource != null;
            assert SwingUtilities.isEventDispatchThread();

            String mimeType = DataFlavorUtils.getFxMimeType(flavor);
            return DataFlavorUtils.adjustFxData(
                    flavor, fxDragSource.getData(mimeType));
        }

        @Override
        public DataFlavor[] getTransferDataFlavors() {
            assert fxDragSource != null;
            assert SwingUtilities.isEventDispatchThread();

            final String mimeTypes[] = fxDragSource.getMimeTypes();

            final ArrayList<DataFlavor> flavors =
                    new ArrayList<>(mimeTypes.length);
            for (String mime : mimeTypes) {
                DataFlavor flavor = null;
                try {
                    flavor = new DataFlavor(mime);
                } catch (ClassNotFoundException e) {
                    // FIXME: what to do?
                    continue;
                }
                flavors.add(flavor);
            }
            return flavors.toArray(new DataFlavor[0]);
        }

        @Override
        public boolean isDataFlavorSupported(final DataFlavor flavor) {
            assert fxDragSource != null;
            assert SwingUtilities.isEventDispatchThread();

            return fxDragSource.isMimeTypeAvailable(
                    DataFlavorUtils.getFxMimeType(flavor));
        }
    }
}
