/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.ui.views.bookmarkexplorer;

import java.util.ArrayList;

import org.eclipse.core.resources.IMarker;
import org.eclipse.core.resources.IResource;
import org.eclipse.core.resources.IWorkspace;
import org.eclipse.core.resources.IWorkspaceRoot;
import org.eclipse.core.resources.ResourcesPlugin;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.Platform;
import org.eclipse.jface.action.Action;
import org.eclipse.jface.action.IMenuListener;
import org.eclipse.jface.action.IMenuManager;
import org.eclipse.jface.action.IToolBarManager;
import org.eclipse.jface.action.MenuManager;
import org.eclipse.jface.action.Separator;
import org.eclipse.jface.dialogs.IDialogSettings;
import org.eclipse.jface.viewers.ColumnLayoutData;
import org.eclipse.jface.viewers.ColumnPixelData;
import org.eclipse.jface.viewers.ColumnWeightData;
import org.eclipse.jface.viewers.ILabelProvider;
import org.eclipse.jface.viewers.IOpenListener;
import org.eclipse.jface.viewers.ISelectionChangedListener;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.OpenEvent;
import org.eclipse.jface.viewers.SelectionChangedEvent;
import org.eclipse.jface.viewers.StructuredSelection;
import org.eclipse.jface.viewers.StructuredViewer;
import org.eclipse.jface.viewers.TableLayout;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.dnd.Clipboard;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.DragSourceAdapter;
import org.eclipse.swt.dnd.DragSourceEvent;
import org.eclipse.swt.dnd.DragSourceListener;
import org.eclipse.swt.dnd.TextTransfer;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.events.KeyAdapter;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.ScrollBar;
import org.eclipse.swt.widgets.Scrollable;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Table;
import org.eclipse.swt.widgets.TableColumn;
import org.eclipse.ui.IActionBars;
import org.eclipse.ui.IMemento;
import org.eclipse.ui.IPageLayout;
import org.eclipse.ui.ISharedImages;
import org.eclipse.ui.IViewSite;
import org.eclipse.ui.IWorkbenchActionConstants;
import org.eclipse.ui.PartInitException;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.actions.ActionFactory;
import org.eclipse.ui.internal.ide.IDEWorkbenchPlugin;
import org.eclipse.ui.internal.views.bookmarkexplorer.BookmarkMessages;
import org.eclipse.ui.part.IShowInSource;
import org.eclipse.ui.part.IShowInTargetList;
import org.eclipse.ui.part.MarkerTransfer;
import org.eclipse.ui.part.ShowInContext;
import org.eclipse.ui.part.ViewPart;
import org.eclipse.ui.plugin.AbstractUIPlugin;
import org.eclipse.ui.views.navigator.ShowInNavigatorAction;

/**
 * Main class for the bookmark navigator for displaying bookmarks on
 * resources and opening an editor on the bookmarked resource when the user
 * commands.
 * <p>
 * This standard view has id <code>"org.eclipse.ui.views.BookmarkNavigator"</code>.
 * </p>
 * <p>
 * The workbench will automatically instantiate this class when a bookmark
 * navigator is needed for a workbench window. This class is not intended
 * to be instantiated or subclassed by clients.
 * </p>
 */
public class BookmarkNavigator extends ViewPart {
    private Table table;

    private TableViewer viewer;

    private OpenBookmarkAction openAction;

    private CopyBookmarkAction copyAction;

    private PasteBookmarkAction pasteAction;

    private RemoveBookmarkAction removeAction;

    private EditBookmarkAction editAction;

    private SelectAllAction selectAllAction;

    private ShowInNavigatorAction showInNavigatorAction;

    private SortByAction sortByDescriptionAction;

    private SortByAction sortByResourceAction;

    private SortByAction sortByFolderAction;

    private SortByAction sortByLineAction;

    private SortByAction sortByCreationTime;

    private ChangeSortDirectionAction sortAscendingAction;

    private ChangeSortDirectionAction sortDescendingAction;

    private IMemento memento;

    private BookmarkSorter sorter;

    private Clipboard clipboard;

    private final String columnHeaders[] = {
            BookmarkMessages.ColumnIcon_header,
            BookmarkMessages.ColumnDescription_header,
            BookmarkMessages.ColumnResource_header,
            BookmarkMessages.ColumnFolder_header,
            BookmarkMessages.ColumnLocation_header };

    private ColumnLayoutData columnLayouts[] = {
			new ColumnPixelData(16, false, true), new ColumnWeightData(200),
			new ColumnWeightData(75), new ColumnWeightData(150),
			new ColumnWeightData(60) };

    // Persistance tags.
    private static final String TAG_SELECTION = "selection"; //$NON-NLS-1$

    private static final String TAG_ID = "id";//$NON-NLS-1$

    private static final String TAG_MARKER = "marker";//$NON-NLS-1$

    private static final String TAG_RESOURCE = "resource";//$NON-NLS-1$

    private static final String TAG_VERTICAL_POSITION = "verticalPosition";//$NON-NLS-1$

    private static final String TAG_HORIZONTAL_POSITION = "horizontalPosition";//$NON-NLS-1$
	
    class SortByAction extends Action {

        private int column;

        /**
         * @param column
         */
        public SortByAction(int column) {
            this.column = column;
        }

        public void run() {
            sorter.setTopPriority(column);
            updateSortState();
            viewer.refresh();
            IDialogSettings workbenchSettings = getPlugin().getDialogSettings();
            IDialogSettings settings = workbenchSettings
                    .getSection("BookmarkSortState");//$NON-NLS-1$
            if (settings == null)
                settings = workbenchSettings.addNewSection("BookmarkSortState");//$NON-NLS-1$
            sorter.saveState(settings);
        }
    }

    class ChangeSortDirectionAction extends Action {

        private int direction;

        /**
         * @param direction
         */
        public ChangeSortDirectionAction(int direction) {
            this.direction = direction;
        }

        public void run() {
            sorter.setTopPriorityDirection(direction);
            updateSortState();
            viewer.refresh();
            IDialogSettings workbenchSettings = getPlugin().getDialogSettings();
            IDialogSettings settings = workbenchSettings
                    .getSection("BookmarkSortState");//$NON-NLS-1$
            if (settings == null)
                settings = workbenchSettings.addNewSection("BookmarkSortState");//$NON-NLS-1$
            sorter.saveState(settings);
        }
    }

    /**
     * Creates the bookmarks view.
     */
    public BookmarkNavigator() {
        super();
    }

    /**
     * Adds this views contributions to the workbench.
     */
    void addContributions() {
        ISharedImages sharedImages = PlatformUI.getWorkbench()
                .getSharedImages();

        // Create the actions.
        openAction = new OpenBookmarkAction(this);
        openAction
                .setImageDescriptor(IDEWorkbenchPlugin.getIDEImageDescriptor("elcl16/gotoobj_tsk.gif"));//$NON-NLS-1$

        copyAction = new CopyBookmarkAction(this);
        copyAction.setImageDescriptor(sharedImages
                .getImageDescriptor(ISharedImages.IMG_TOOL_COPY));

        pasteAction = new PasteBookmarkAction(this);
        pasteAction.setImageDescriptor(sharedImages
                .getImageDescriptor(ISharedImages.IMG_TOOL_PASTE));

        removeAction = new RemoveBookmarkAction(this);
        removeAction.setImageDescriptor(sharedImages
                .getImageDescriptor(ISharedImages.IMG_TOOL_DELETE));
        removeAction.setDisabledImageDescriptor(sharedImages
                .getImageDescriptor(ISharedImages.IMG_TOOL_DELETE_DISABLED));

        editAction = new EditBookmarkAction(this);

        selectAllAction = new SelectAllAction(this);
        showInNavigatorAction = new ShowInNavigatorAction(getViewSite()
                .getPage(), viewer);

        // initializes action enabled state
        handleSelectionChanged(StructuredSelection.EMPTY);

        // Create dynamic menu mgr.  Dynamic is currently required to
        // support action contributions.
        MenuManager mgr = new MenuManager();
        mgr.setRemoveAllWhenShown(true);
        mgr.addMenuListener(new IMenuListener() {
            public void menuAboutToShow(IMenuManager mgr) {
                fillContextMenu(mgr);
            }
        });
        Menu menu = mgr.createContextMenu(viewer.getControl());
        viewer.getControl().setMenu(menu);
        getSite().registerContextMenu(mgr, viewer);

        // Add actions to the local tool bar
        IToolBarManager tbm = getViewSite().getActionBars().getToolBarManager();
        tbm.add(removeAction);
        tbm.add(openAction);
        tbm.update(false);

        // Register with action service.
        IActionBars actionBars = getViewSite().getActionBars();
        actionBars.setGlobalActionHandler(ActionFactory.COPY.getId(),
                copyAction);
        actionBars.setGlobalActionHandler(ActionFactory.PASTE.getId(),
                pasteAction);
        actionBars.setGlobalActionHandler(ActionFactory.DELETE.getId(),
                removeAction);
        actionBars.setGlobalActionHandler(ActionFactory.SELECT_ALL.getId(),
                selectAllAction);

        // Set the double click action.
        viewer.addOpenListener(new IOpenListener() {
            public void open(OpenEvent event) {
                openAction.run();
            }
        });
        viewer.addSelectionChangedListener(new ISelectionChangedListener() {
            public void selectionChanged(SelectionChangedEvent event) {
                handleSelectionChanged((IStructuredSelection) event
                        .getSelection());
            }
        });
        viewer.getControl().addKeyListener(new KeyAdapter() {
            public void keyPressed(KeyEvent e) {
                handleKeyPressed(e);
            }
        });
    }

    /* (non-Javadoc)
     * Method declared on IWorkbenchPart.
     */
    public void createPartControl(Composite parent) {
        clipboard = new Clipboard(parent.getDisplay());
        createTable(parent);
        viewer = new TableViewer(table);
        createColumns();

        sorter = new BookmarkSorter();
        viewer.setContentProvider(new BookmarkContentProvider(this));
        viewer.setLabelProvider(new BookmarkLabelProvider(this));
        viewer.setInput(ResourcesPlugin.getWorkspace().getRoot());
        viewer.setSorter(sorter);

        IDialogSettings workbenchSettings = getPlugin().getDialogSettings();
        IDialogSettings settings = workbenchSettings
                .getSection("BookmarkSortState");//$NON-NLS-1$
        sorter.restoreState(settings);

        addContributions();
        initDragAndDrop();
        createSortActions();
        fillActionBars();
        updateSortState();
        updatePasteEnablement();

        getSite().setSelectionProvider(viewer);

        if (memento != null)
            restoreState(memento);
        memento = null;

        PlatformUI.getWorkbench().getHelpSystem().setHelp(viewer.getControl(),
                IBookmarkHelpContextIds.BOOKMARK_VIEW);
    }

    public void dispose() {
        if (clipboard != null)
            clipboard.dispose();
    }

    /**
     * Notifies this listener that the menu is about to be shown by
     * the given menu manager.
     *
     * @param manager the menu manager
     */
    void fillContextMenu(IMenuManager manager) {
        manager.add(openAction);
        manager.add(copyAction);
        updatePasteEnablement();
        manager.add(pasteAction);
        manager.add(removeAction);
        manager.add(selectAllAction);
        manager.add(showInNavigatorAction);
        manager.add(new Separator(IWorkbenchActionConstants.MB_ADDITIONS));
        manager.add(new Separator());
        manager.add(editAction);
    }

    /* (non-Javadoc)
     * @see org.eclipse.core.runtime.IAdaptable#getAdapter(Class)
     */
    public Object getAdapter(Class adapter) {
        if (adapter == IShowInSource.class) {
            return new IShowInSource() {
                public ShowInContext getShowInContext() {
                    return new ShowInContext(null, getViewer().getSelection());
                }
            };
        }
        if (adapter == IShowInTargetList.class) {
            return new IShowInTargetList() {
                public String[] getShowInTargetIds() {
                    return new String[] { IPageLayout.ID_RES_NAV };
                }

            };
        }
        return super.getAdapter(adapter);
    }

    /**
     * Returns the UI plugin for the bookmarks view.
     */
    static AbstractUIPlugin getPlugin() {
        return (AbstractUIPlugin) Platform.getPlugin(PlatformUI.PLUGIN_ID);
    }

    /**
     * Returns the shell.
     */
    Shell getShell() {
        return getViewSite().getShell();
    }

    /**
     * Returns the viewer used to display bookmarks.
     *
     * @return the viewer, or <code>null</code> if this view's controls
     *  have not been created yet
     */
    StructuredViewer getViewer() {
        return viewer;
    }

    /**
     * Returns the workspace.
     */
    IWorkspace getWorkspace() {
        return ResourcesPlugin.getWorkspace();
    }

    /**
     * Handles key events in viewer.
     */
    void handleKeyPressed(KeyEvent event) {
        if (event.character == SWT.DEL && event.stateMask == 0
                && removeAction.isEnabled())
            removeAction.run();
    }

    /**
     * Handles a selection change.
     *
     * @param selection the new selection
     */
    void handleSelectionChanged(IStructuredSelection selection) {
        //update the actions
        openAction.selectionChanged(selection);
        removeAction.selectionChanged(selection);
        editAction.selectionChanged(selection);
        selectAllAction.selectionChanged(selection);
        showInNavigatorAction.selectionChanged(selection);
    }

    /* (non-Javadoc)
     * Method declared on IViewPart.
     */
    public void init(IViewSite site, IMemento memento) throws PartInitException {
        super.init(site, memento);
        this.memento = memento;
    }

    /**
     * Adds drag and drop support to the bookmark navigator.
     */
    protected void initDragAndDrop() {
        int operations = DND.DROP_COPY;
        Transfer[] transferTypes = new Transfer[] {
                MarkerTransfer.getInstance(), TextTransfer.getInstance() };
        DragSourceListener listener = new DragSourceAdapter() {
            public void dragSetData(DragSourceEvent event) {
                performDragSetData(event);
            }

            public void dragFinished(DragSourceEvent event) {
            }
        };
        viewer.addDragSupport(operations, transferTypes, listener);
    }

    /**
     * The user is attempting to drag marker data.  Add the appropriate
     * data to the event depending on the transfer type.
     */
    void performDragSetData(DragSourceEvent event) {
        if (MarkerTransfer.getInstance().isSupportedType(event.dataType)) {
            event.data = ((IStructuredSelection) viewer.getSelection())
                    .toArray();
            return;
        }
        if (TextTransfer.getInstance().isSupportedType(event.dataType)) {
            Object[] markers = ((IStructuredSelection) viewer.getSelection())
                    .toArray();
            if (markers != null) {
                StringBuffer buffer = new StringBuffer();
                ILabelProvider provider = (ILabelProvider) getViewer()
                        .getLabelProvider();
                for (int i = 0; i < markers.length; i++) {
                    if (i > 0)
                        buffer.append(System.getProperty("line.separator")); //$NON-NLS-1$
                    String text = provider.getText(markers[i]);
                    if(text != null)
                    	buffer.append(text);
                }
                event.data = buffer.toString();
            }
            return;
        }
    }

    void restoreState(IMemento memento) {
        IWorkspaceRoot root = ResourcesPlugin.getWorkspace().getRoot();
        IMemento selectionMem = memento.getChild(TAG_SELECTION);
        if (selectionMem != null) {
            ArrayList selectionList = new ArrayList();
            IMemento markerMems[] = selectionMem.getChildren(TAG_MARKER);
            for (int i = 0; i < markerMems.length; i++) {
                try {
                    long id = new Long(markerMems[i].getString(TAG_ID))
                            .longValue();
                    IResource resource = root.findMember(markerMems[i]
                            .getString(TAG_RESOURCE));
                    if (resource != null) {
                        IMarker marker = resource.findMarker(id);
                        if (marker != null)
                            selectionList.add(marker);
                    }
                } catch (CoreException e) {
                }
            }
            viewer.setSelection(new StructuredSelection(selectionList));
        }

        Scrollable scrollable = (Scrollable) viewer.getControl();
        //save vertical position
        ScrollBar bar = scrollable.getVerticalBar();
        if (bar != null) {
            try {
                String posStr = memento.getString(TAG_VERTICAL_POSITION);
                int position;
                position = new Integer(posStr).intValue();
                bar.setSelection(position);
            } catch (NumberFormatException e) {
            }
        }
        bar = scrollable.getHorizontalBar();
        if (bar != null) {
            try {
                String posStr = memento.getString(TAG_HORIZONTAL_POSITION);
                int position;
                position = new Integer(posStr).intValue();
                bar.setSelection(position);
            } catch (NumberFormatException e) {
            }
        }

        updateSortState();
        viewer.refresh();
    }

    public void saveState(IMemento memento) {
        if (viewer == null) {
            if (this.memento != null) //Keep the old state;
                memento.putMemento(this.memento);
            return;
        }

        Scrollable scrollable = (Scrollable) viewer.getControl();
        Object markers[] = ((IStructuredSelection) viewer.getSelection())
                .toArray();
        if (markers.length > 0) {
            IMemento selectionMem = memento.createChild(TAG_SELECTION);
            for (int i = 0; i < markers.length; i++) {
                IMemento elementMem = selectionMem.createChild(TAG_MARKER);
                IMarker marker = (IMarker) markers[i];
                elementMem.putString(TAG_RESOURCE, marker.getResource()
                        .getFullPath().toString());
                elementMem.putString(TAG_ID, String.valueOf(marker.getId()));
            }
        }

        //save vertical position
        ScrollBar bar = scrollable.getVerticalBar();
        int position = bar != null ? bar.getSelection() : 0;
        memento.putString(TAG_VERTICAL_POSITION, String.valueOf(position));
        //save horizontal position
        bar = scrollable.getHorizontalBar();
        position = bar != null ? bar.getSelection() : 0;
        memento.putString(TAG_HORIZONTAL_POSITION, String.valueOf(position));

    }

    /* (non-Javadoc)
     * Method declared on IWorkbenchPart.
     */
    public void setFocus() {
        if (viewer != null)
            viewer.getControl().setFocus();
    }

    void createColumns() {
        SelectionListener headerListener = new SelectionAdapter() {
            /**
             * Handles the case of user selecting the
             * header area.
             * <p>If the column has not been selected previously,
             * it will set the sorter of that column to be
             * the current tasklist sorter. Repeated
             * presses on the same column header will
             * toggle sorting order (ascending/descending).
             */
            public void widgetSelected(SelectionEvent e) {
                // column selected - first column doesn't count
                int column = table.indexOf((TableColumn) e.widget) - 1;
                if (column == sorter.getTopPriority())
                    sorter.reverseTopPriority();
                else {
                    sorter.setTopPriority(column);
                }
                updateSortState();
                viewer.refresh();
                IDialogSettings workbenchSettings = getPlugin()
                        .getDialogSettings();
                IDialogSettings settings = workbenchSettings
                        .getSection("BookmarkSortState");//$NON-NLS-1$
                if (settings == null)
                    settings = workbenchSettings
                            .addNewSection("BookmarkSortState");//$NON-NLS-1$
                sorter.saveState(settings);
            }
        };

        TableLayout layout = new TableLayout();
        table.setLayout(layout);
        table.setHeaderVisible(true);
        for (int i = 0; i < columnHeaders.length; i++) {
            layout.addColumnData(columnLayouts[i]);
            TableColumn tc = new TableColumn(table, SWT.NONE, i);
            tc.setResizable(columnLayouts[i].resizable);
            tc.setText(columnHeaders[i]);
            if (i > 0)
                tc.addSelectionListener(headerListener);
        }
    }

    /**
     * Creates the table control.
     */
    void createTable(Composite parent) {
        table = new Table(parent, SWT.H_SCROLL | SWT.V_SCROLL | SWT.MULTI
                | SWT.FULL_SELECTION);
        table.setLinesVisible(true);
        //table.setLayout(new TableLayout());
    }

    /**
     * Fills the local tool bar and menu manager with actions.
     */
    void fillActionBars() {
        IActionBars actionBars = getViewSite().getActionBars();
        IMenuManager menu = actionBars.getMenuManager();
        IMenuManager submenu = new MenuManager(BookmarkMessages.SortMenuGroup_text);
        menu.add(submenu);
        submenu.add(sortByDescriptionAction);
        submenu.add(sortByResourceAction);
        submenu.add(sortByFolderAction);
        submenu.add(sortByLineAction);
        submenu.add(sortByCreationTime);
        submenu.add(new Separator());
        submenu.add(sortAscendingAction);
        submenu.add(sortDescendingAction);
    }

    void createSortActions() {
        sortByDescriptionAction = new SortByAction(BookmarkSorter.DESCRIPTION);
        sortByDescriptionAction.setText(BookmarkMessages.ColumnDescription_text);
        PlatformUI.getWorkbench().getHelpSystem().setHelp(
				sortByDescriptionAction,
				IBookmarkHelpContextIds.SORT_DESCRIPTION_ACTION);

        sortByResourceAction = new SortByAction(BookmarkSorter.RESOURCE);
        sortByResourceAction.setText(BookmarkMessages.ColumnResource_text);
        PlatformUI.getWorkbench().getHelpSystem().setHelp(sortByResourceAction,
                IBookmarkHelpContextIds.SORT_RESOURCE_ACTION);

        sortByFolderAction = new SortByAction(BookmarkSorter.FOLDER);
        sortByFolderAction.setText(BookmarkMessages.ColumnFolder_text);
        PlatformUI.getWorkbench().getHelpSystem().setHelp(sortByFolderAction,
                IBookmarkHelpContextIds.SORT_FOLDER_ACTION);

        sortByLineAction = new SortByAction(BookmarkSorter.LOCATION);
        sortByLineAction.setText(BookmarkMessages.ColumnLocation_text);
        PlatformUI.getWorkbench().getHelpSystem().setHelp(sortByLineAction,
                IBookmarkHelpContextIds.SORT_LOCATION_ACTION);

        sortByCreationTime = new SortByAction(BookmarkSorter.CREATION_TIME);
        sortByCreationTime.setText(BookmarkMessages.ColumnCreationTime_text);
        PlatformUI.getWorkbench().getHelpSystem().setHelp(sortByCreationTime,
                IBookmarkHelpContextIds.SORT_CREATION_TIME_ACTION);

        sortAscendingAction = new ChangeSortDirectionAction(
                BookmarkSorter.ASCENDING);
        sortAscendingAction.setText(BookmarkMessages.SortDirectionAscending_text);
        PlatformUI.getWorkbench().getHelpSystem().setHelp(sortAscendingAction,
                IBookmarkHelpContextIds.SORT_ASCENDING_ACTION);

        sortDescendingAction = new ChangeSortDirectionAction(
                BookmarkSorter.DESCENDING);
        sortDescendingAction.setText(BookmarkMessages.SortDirectionDescending_text);
        PlatformUI.getWorkbench().getHelpSystem().setHelp(sortDescendingAction,
                IBookmarkHelpContextIds.SORT_DESCENDING_ACTION);
    }

    void updateSortState() {
        int column = sorter.getTopPriority();
        sortByDescriptionAction
                .setChecked(column == BookmarkSorter.DESCRIPTION);
        sortByResourceAction.setChecked(column == BookmarkSorter.RESOURCE);
        sortByFolderAction.setChecked(column == BookmarkSorter.FOLDER);
        sortByLineAction.setChecked(column == BookmarkSorter.LOCATION);
        sortByCreationTime.setChecked(column == BookmarkSorter.CREATION_TIME);

        int direction = sorter.getTopPriorityDirection();
        sortAscendingAction.setChecked(direction == BookmarkSorter.ASCENDING);
        sortDescendingAction.setChecked(direction == BookmarkSorter.DESCENDING);
    }

    /**
     * Updates the enablement of the paste action
     */
    void updatePasteEnablement() {
        // Paste if clipboard contains tasks
        MarkerTransfer transfer = MarkerTransfer.getInstance();
        IMarker[] markerData = (IMarker[]) getClipboard().getContents(transfer);
        boolean canPaste = false;
        if (markerData != null) {
            for (int i = 0; i < markerData.length; i++) {
                try {
                    if (markerData[i].getType().equals(IMarker.BOOKMARK)) {
                        canPaste = true;
                        break;
                    }
                } catch (CoreException e) {
                    canPaste = false;
                }
            }
        }
        pasteAction.setEnabled(canPaste);
    }

    Clipboard getClipboard() {
        return clipboard;
    }

}