bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/markers/internal/TableView.java - platform/eclipse.platform.ui - Git at Google

 /*******************************************************************************
  * Copyright (c) 2000, 2003 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Common Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/cpl-v10.html
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *******************************************************************************/

 package org.eclipse.ui.views.markers.internal;

 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;

 import org.eclipse.jface.action.IAction;
 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.dialogs.Dialog;
 import org.eclipse.jface.dialogs.IDialogSettings;
 import org.eclipse.jface.viewers.ColumnLayoutData;
 import org.eclipse.jface.viewers.ColumnPixelData;
 import org.eclipse.jface.viewers.IOpenListener;
 import org.eclipse.jface.viewers.IStructuredSelection;
 import org.eclipse.jface.viewers.OpenEvent;
 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.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.Table;
 import org.eclipse.swt.widgets.TableColumn;
 import org.eclipse.ui.IActionBars;
 import org.eclipse.ui.IMemento;
 import org.eclipse.ui.IViewSite;
 import org.eclipse.ui.PartInitException;
 import org.eclipse.ui.part.ViewPart;

 public abstract class TableView extends ViewPart {

 	private static final String TAG_COLUMN_WIDTH = "columnWidth"; //$NON-NLS-1$
 	private static final String TAG_VERTICAL_POSITION = "verticalPosition"; //$NON-NLS-1$
 	private static final String TAG_HORIZONTAL_POSITION = "horizontalPosition"; //$NON-NLS-1$

 	public static final String SORT_ACTION_ID = "sort"; //$NON-NLS-1$
 	public static final String FILTERS_ACTION_ID = "filters"; //$NON-NLS-1$

 	private TableViewer viewer;
 	private Clipboard clipboard;
 	private IMemento memento;
 	protected ColumnLayoutData[] columnLayouts;

 	private Map actions = new HashMap();

 	private TableSorter sorter;

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

 	/* (non-Javadoc)
 	 * @see org.eclipse.ui.part.WorkbenchPart#createPartControl(org.eclipse.swt.widgets.Composite)
 	 */
 	public void createPartControl(Composite parent) {
 		viewer = new TableViewer(createTable(parent));
 		restoreColumnWidths(memento);
 		createColumns(viewer.getTable());
 		getContentProvider().setFilter(getFilter());
 		viewer.setContentProvider(new TableContentProvider(getSite(), getContentProvider()));
 		viewer.setLabelProvider(new TableViewLabelProvider(getVisibleFields()));

 		viewer.setSorter(getSorter());

 		//create the actions before the input is set on the viewer but after the
 		//sorter and filter are set so the actions will be enabled correctly.
 		createActions();

 		viewer.setInput(getViewerInput());
 		viewer.setSelection(restoreSelection(memento), true);
 		Scrollable scrollable = (Scrollable) viewer.getControl();
 		ScrollBar bar = scrollable.getVerticalBar();
 		if (bar != null) {
 			bar.setSelection(restoreVerticalScrollBarPosition(memento));
 		}
 		bar = scrollable.getHorizontalBar();
 		if (bar != null) {
 			bar.setSelection(restoreHorizontalScrollBarPosition(memento));
 		}

 		MenuManager mgr = initContextMenu();
 		Menu menu = mgr.createContextMenu(viewer.getControl());
 		viewer.getControl().setMenu(menu);
 		getSite().registerContextMenu(mgr, viewer);
 		initActionBars(getViewSite().getActionBars());
 		registerGlobalActions(getViewSite().getActionBars());

 		viewer.addOpenListener(new IOpenListener() {
 			public void open(OpenEvent event) {
 				handleOpenEvent(event);
 			}
 		});
 		viewer.getControl().addKeyListener(new KeyAdapter() {
 			public void keyPressed(KeyEvent e) {
 				handleKeyPressed(e);
 			}
 		});
 	}

 	/* (non-Javadoc)
 	 * @see org.eclipse.ui.IWorkbenchPart#dispose()
 	 */
 	public void dispose() {
 	}

 	/**
 	 * Creates the table control.
 	 */
 	protected Table createTable(Composite parent) {
 		Table table = new Table(parent, SWT.H_SCROLL | SWT.V_SCROLL | SWT.MULTI | SWT.FULL_SELECTION);
 		table.setLinesVisible(true);
 		table.setFont(parent.getFont());
 		return table;
 	}

 	protected void createColumns(final Table table) {
 		SelectionListener headerListener = getHeaderListener();
 		TableLayout layout = new TableLayout();
 		table.setLayout(layout);
 		table.setHeaderVisible(true);
 		final IField[] fields = getVisibleFields();
 		ColumnLayoutData[] columnWidths = columnLayouts;
 		if (columnWidths == null) {
 			columnWidths = getDefaultColumnLayouts();
 		}
 		for (int i = 0; i < fields.length; i++) {
 			if (columnWidths == null || i >= columnWidths.length || columnWidths[i] == null) {
 				layout.addColumnData(new ColumnPixelData(504 / fields.length, true));
 			}
 			else {
 				layout.addColumnData(columnWidths[i]);
 			}
 			TableColumn tc = new TableColumn(table, SWT.NONE,i);
 			tc.setText(fields[i].getColumnHeaderText());
 			tc.setImage(fields[i].getColumnHeaderImage());
 			tc.addSelectionListener(headerListener);
 		}
 	}

 	protected void createActions() {
 		if (getSortDialog() != null) {
 			putAction(SORT_ACTION_ID, new TableSortAction(this, getSortDialog()));
 		}
 		if (getFiltersDialog() != null) {
 			putAction(FILTERS_ACTION_ID, new FiltersAction(this, getFiltersDialog()));
 		}
 	}

 	protected IAction getAction(String id) {
 		return (IAction) actions.get(id);
 	}

 	protected void putAction(String id, IAction action) {
 		actions.put(id, action);
 	}

 	protected MenuManager initContextMenu() {
 		MenuManager mgr = new MenuManager();
 		mgr.setRemoveAllWhenShown(true);
 		mgr.addMenuListener(new IMenuListener() {
 			public void menuAboutToShow(IMenuManager mgr) {
 				getViewer().cancelEditing();
 				fillContextMenu(mgr);
 			}
 		});
 		return mgr;
 	}

 	protected abstract void initToolBar(IToolBarManager tbm);

 	protected void initActionBars(IActionBars actionBars) {
 		initMenu(actionBars.getMenuManager());
 		initToolBar(actionBars.getToolBarManager());
 	}

 	protected void initMenu(IMenuManager menu) {
 		IAction sortAction = getAction(SORT_ACTION_ID);
 		if (sortAction != null)
 			menu.add(sortAction);
 		IAction filtersAction = getAction(FILTERS_ACTION_ID);
 		if (filtersAction != null)
 			menu.add(filtersAction);
 	}

 	protected abstract void registerGlobalActions(IActionBars actionBars);

 	protected abstract void fillContextMenu(IMenuManager manager);

 	/* (non-Javadoc)
 	 * @see org.eclipse.ui.part.WorkbenchPart#setFocus()
 	 */
 	public void setFocus() {
 		TableViewer viewer = getViewer();
 		if (viewer != null && !viewer.getControl().isDisposed()) {
 			viewer.getControl().setFocus();
 		}
 	}

 	protected abstract IFilter getFilter();

 	protected TableSorter getSorter() {
 		if (sorter == null) {
 			int[] priorities = new int[getFields().length];
 			int[] directions = new int[getFields().length];
 			for (int i = 0; i < getFields().length; i++) {
 				priorities[i] = i;
 			}
 			Arrays.fill(directions, TableSorter.ASCENDING);
 			sorter = new TableSorter(getFields(), priorities, directions);
 			sorter.restoreState(getDialogSettings());
 		}
 		return sorter;
 	}

 	protected abstract ITableViewContentProvider getContentProvider();

 	protected IField[] getFields() {
 		IField[] vProps = getVisibleFields();
 		IField[] hProps = getHiddenFields();
 		IField[] fields = new IField[vProps.length + hProps.length];
 		System.arraycopy(vProps, 0, fields, 0, vProps.length);
 		System.arraycopy(hProps, 0, fields, vProps.length, hProps.length);
 		return fields;
 	}

 	protected abstract Object getViewerInput();

 	protected abstract IField[] getVisibleFields();

 	protected abstract IField[] getHiddenFields();

 	protected abstract IDialogSettings getDialogSettings();

 	protected TableViewer getViewer() {
 		return viewer;
 	}

 	protected SelectionListener getHeaderListener() {
 		return new SelectionAdapter() {
 			/**
 			 * Handles the case of user selecting the
 			 * header area.
 			 */
 			public void widgetSelected(SelectionEvent e) {
 				int column = getViewer().getTable().indexOf((TableColumn) e.widget);
 				if (column == getSorter().getTopPriority())
 					getSorter().reverseTopPriority();
 				else {
 					getSorter().setTopPriority(column);
 				}
 				viewer.refresh(false);
 				getSorter().saveState(getDialogSettings());
 			}
 		};
 	}

 	protected abstract ColumnLayoutData[] getDefaultColumnLayouts();

 	protected TableSortDialog getSortDialog() {
 		if (getSorter() != null) {
 			return new TableSortDialog(getSite().getShell(), getSorter());
 		}
 		return null;
 	}

 	protected abstract Dialog getFiltersDialog();

 	protected void filtersChanged() {
 		final TableViewer viewer = getViewer();
 		if (viewer == null) {
 			return;
 		}
 		getSite().getShell().getDisplay().asyncExec(new Runnable() {
 			public void run() {
 				viewer.getControl().setRedraw(false);
 				viewer.refresh(false);
 				viewer.getControl().setRedraw(true);
 			}
 		});
 	}

 	protected void sorterChanged() {
 		final TableViewer viewer = getViewer();
 		if (viewer == null) {
 			return;
 		}
 		getSite().getShell().getDisplay().asyncExec(new Runnable() {
 			public void run() {
 				viewer.getControl().setRedraw(false);
 				viewer.refresh(false);
 				viewer.getControl().setRedraw(true);
 			}
 		});
 	}

 	protected abstract void handleKeyPressed(KeyEvent event);

 	protected abstract void handleOpenEvent(OpenEvent event);

 	/* (non-Javadoc)
 	 * @see org.eclipse.ui.part.ViewPart#saveState(org.eclipse.ui.IMemento)
 	 */
 	public void saveState(IMemento memento) {
 		super.saveState(memento);

 		//save column widths
 		TableColumn[] columns = viewer.getTable().getColumns();
 		for (int i = 0; i < columns.length; i++) {
 			memento.putInteger(TAG_COLUMN_WIDTH + i, columns[i].getWidth());
 		}

 		saveSelection(memento);

 		//save vertical position
 		Scrollable scrollable = (Scrollable) viewer.getControl();
 		ScrollBar bar = scrollable.getVerticalBar();
 		int position = (bar != null) ? bar.getSelection() : 0;
 		memento.putInteger(TAG_VERTICAL_POSITION, position);
 		//save horizontal position
 		bar = scrollable.getHorizontalBar();
 		position = (bar != null) ? bar.getSelection() : 0;
 		memento.putInteger(TAG_HORIZONTAL_POSITION, position);
 	}

 	protected abstract void saveSelection(IMemento memento);

 	private void restoreColumnWidths(IMemento memento) {
 		if (memento == null) {
 			return;
 		}
 		columnLayouts = new ColumnLayoutData[getFields().length];
 		for (int i = 0; i < columnLayouts.length; i++) {
 			Integer width = memento.getInteger(TAG_COLUMN_WIDTH + i);
 			if (width == null) {
 				columnLayouts = null;
 				break;
 			}
 			else {
 				columnLayouts[i] = new ColumnPixelData(width.intValue(), true);
 			}
 		}
 	}

 	protected abstract IStructuredSelection restoreSelection(IMemento memento);

 	private int restoreVerticalScrollBarPosition(IMemento memento) {
 		if (memento == null) {
 			return 0;
 		}
 		Integer position = memento.getInteger(TAG_VERTICAL_POSITION);
 		return (position == null) ? 0 : position.intValue();
 	}

 	private int restoreHorizontalScrollBarPosition(IMemento memento) {
 		if (memento == null) {
 			return 0;
 		}
 		Integer position = memento.getInteger(TAG_HORIZONTAL_POSITION);
 		return (position == null) ? 0 : position.intValue();
 	}

 }
	/*******************************************************************************
	* Copyright (c) 2000, 2003 IBM Corporation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Common Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/cpl-v10.html
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	*******************************************************************************/

	package org.eclipse.ui.views.markers.internal;

	import java.util.Arrays;
	import java.util.HashMap;
	import java.util.Map;

	import org.eclipse.jface.action.IAction;
	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.dialogs.Dialog;
	import org.eclipse.jface.dialogs.IDialogSettings;
	import org.eclipse.jface.viewers.ColumnLayoutData;
	import org.eclipse.jface.viewers.ColumnPixelData;
	import org.eclipse.jface.viewers.IOpenListener;
	import org.eclipse.jface.viewers.IStructuredSelection;
	import org.eclipse.jface.viewers.OpenEvent;
	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.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.Table;
	import org.eclipse.swt.widgets.TableColumn;
	import org.eclipse.ui.IActionBars;
	import org.eclipse.ui.IMemento;
	import org.eclipse.ui.IViewSite;
	import org.eclipse.ui.PartInitException;
	import org.eclipse.ui.part.ViewPart;

	public abstract class TableView extends ViewPart {

	private static final String TAG_COLUMN_WIDTH = "columnWidth"; //$NON-NLS-1$
	private static final String TAG_VERTICAL_POSITION = "verticalPosition"; //$NON-NLS-1$
	private static final String TAG_HORIZONTAL_POSITION = "horizontalPosition"; //$NON-NLS-1$

	public static final String SORT_ACTION_ID = "sort"; //$NON-NLS-1$
	public static final String FILTERS_ACTION_ID = "filters"; //$NON-NLS-1$

	private TableViewer viewer;
	private Clipboard clipboard;
	private IMemento memento;
	protected ColumnLayoutData[] columnLayouts;

	private Map actions = new HashMap();

	private TableSorter sorter;

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

	/* (non-Javadoc)
	* @see org.eclipse.ui.part.WorkbenchPart#createPartControl(org.eclipse.swt.widgets.Composite)
	*/
	public void createPartControl(Composite parent) {
	viewer = new TableViewer(createTable(parent));
	restoreColumnWidths(memento);
	createColumns(viewer.getTable());
	getContentProvider().setFilter(getFilter());
	viewer.setContentProvider(new TableContentProvider(getSite(), getContentProvider()));
	viewer.setLabelProvider(new TableViewLabelProvider(getVisibleFields()));

	viewer.setSorter(getSorter());

	//create the actions before the input is set on the viewer but after the
	//sorter and filter are set so the actions will be enabled correctly.
	createActions();

	viewer.setInput(getViewerInput());
	viewer.setSelection(restoreSelection(memento), true);
	Scrollable scrollable = (Scrollable) viewer.getControl();
	ScrollBar bar = scrollable.getVerticalBar();
	if (bar != null) {
	bar.setSelection(restoreVerticalScrollBarPosition(memento));
	}
	bar = scrollable.getHorizontalBar();
	if (bar != null) {
	bar.setSelection(restoreHorizontalScrollBarPosition(memento));
	}

	MenuManager mgr = initContextMenu();
	Menu menu = mgr.createContextMenu(viewer.getControl());
	viewer.getControl().setMenu(menu);
	getSite().registerContextMenu(mgr, viewer);
	initActionBars(getViewSite().getActionBars());
	registerGlobalActions(getViewSite().getActionBars());

	viewer.addOpenListener(new IOpenListener() {
	public void open(OpenEvent event) {
	handleOpenEvent(event);
	}
	});
	viewer.getControl().addKeyListener(new KeyAdapter() {
	public void keyPressed(KeyEvent e) {
	handleKeyPressed(e);
	}
	});
	}

	/* (non-Javadoc)
	* @see org.eclipse.ui.IWorkbenchPart#dispose()
	*/
	public void dispose() {
	}

	/**
	* Creates the table control.
	*/
	protected Table createTable(Composite parent) {
	Table table = new Table(parent, SWT.H_SCROLL \| SWT.V_SCROLL \| SWT.MULTI \| SWT.FULL_SELECTION);
	table.setLinesVisible(true);
	table.setFont(parent.getFont());
	return table;
	}

	protected void createColumns(final Table table) {
	SelectionListener headerListener = getHeaderListener();
	TableLayout layout = new TableLayout();
	table.setLayout(layout);
	table.setHeaderVisible(true);
	final IField[] fields = getVisibleFields();
	ColumnLayoutData[] columnWidths = columnLayouts;
	if (columnWidths == null) {
	columnWidths = getDefaultColumnLayouts();
	}
	for (int i = 0; i < fields.length; i++) {
	if (columnWidths == null \|\| i >= columnWidths.length \|\| columnWidths[i] == null) {
	layout.addColumnData(new ColumnPixelData(504 / fields.length, true));
	}
	else {
	layout.addColumnData(columnWidths[i]);
	}
	TableColumn tc = new TableColumn(table, SWT.NONE,i);
	tc.setText(fields[i].getColumnHeaderText());
	tc.setImage(fields[i].getColumnHeaderImage());
	tc.addSelectionListener(headerListener);
	}
	}

	protected void createActions() {
	if (getSortDialog() != null) {
	putAction(SORT_ACTION_ID, new TableSortAction(this, getSortDialog()));
	}
	if (getFiltersDialog() != null) {
	putAction(FILTERS_ACTION_ID, new FiltersAction(this, getFiltersDialog()));
	}
	}

	protected IAction getAction(String id) {
	return (IAction) actions.get(id);
	}

	protected void putAction(String id, IAction action) {
	actions.put(id, action);
	}

	protected MenuManager initContextMenu() {
	MenuManager mgr = new MenuManager();
	mgr.setRemoveAllWhenShown(true);
	mgr.addMenuListener(new IMenuListener() {
	public void menuAboutToShow(IMenuManager mgr) {
	getViewer().cancelEditing();
	fillContextMenu(mgr);
	}
	});
	return mgr;
	}

	protected abstract void initToolBar(IToolBarManager tbm);

	protected void initActionBars(IActionBars actionBars) {
	initMenu(actionBars.getMenuManager());
	initToolBar(actionBars.getToolBarManager());
	}

	protected void initMenu(IMenuManager menu) {
	IAction sortAction = getAction(SORT_ACTION_ID);
	if (sortAction != null)
	menu.add(sortAction);
	IAction filtersAction = getAction(FILTERS_ACTION_ID);
	if (filtersAction != null)
	menu.add(filtersAction);
	}

	protected abstract void registerGlobalActions(IActionBars actionBars);

	protected abstract void fillContextMenu(IMenuManager manager);

	/* (non-Javadoc)
	* @see org.eclipse.ui.part.WorkbenchPart#setFocus()
	*/
	public void setFocus() {
	TableViewer viewer = getViewer();
	if (viewer != null && !viewer.getControl().isDisposed()) {
	viewer.getControl().setFocus();
	}
	}

	protected abstract IFilter getFilter();

	protected TableSorter getSorter() {
	if (sorter == null) {
	int[] priorities = new int[getFields().length];
	int[] directions = new int[getFields().length];
	for (int i = 0; i < getFields().length; i++) {
	priorities[i] = i;
	}
	Arrays.fill(directions, TableSorter.ASCENDING);
	sorter = new TableSorter(getFields(), priorities, directions);
	sorter.restoreState(getDialogSettings());
	}
	return sorter;
	}

	protected abstract ITableViewContentProvider getContentProvider();

	protected IField[] getFields() {
	IField[] vProps = getVisibleFields();
	IField[] hProps = getHiddenFields();
	IField[] fields = new IField[vProps.length + hProps.length];
	System.arraycopy(vProps, 0, fields, 0, vProps.length);
	System.arraycopy(hProps, 0, fields, vProps.length, hProps.length);
	return fields;
	}

	protected abstract Object getViewerInput();

	protected abstract IField[] getVisibleFields();

	protected abstract IField[] getHiddenFields();

	protected abstract IDialogSettings getDialogSettings();

	protected TableViewer getViewer() {
	return viewer;
	}

	protected SelectionListener getHeaderListener() {
	return new SelectionAdapter() {
	/**
	* Handles the case of user selecting the
	* header area.
	*/
	public void widgetSelected(SelectionEvent e) {
	int column = getViewer().getTable().indexOf((TableColumn) e.widget);
	if (column == getSorter().getTopPriority())
	getSorter().reverseTopPriority();
	else {
	getSorter().setTopPriority(column);
	}
	viewer.refresh(false);
	getSorter().saveState(getDialogSettings());
	}
	};
	}

	protected abstract ColumnLayoutData[] getDefaultColumnLayouts();

	protected TableSortDialog getSortDialog() {
	if (getSorter() != null) {
	return new TableSortDialog(getSite().getShell(), getSorter());
	}
	return null;
	}

	protected abstract Dialog getFiltersDialog();

	protected void filtersChanged() {
	final TableViewer viewer = getViewer();
	if (viewer == null) {
	return;
	}
	getSite().getShell().getDisplay().asyncExec(new Runnable() {
	public void run() {
	viewer.getControl().setRedraw(false);
	viewer.refresh(false);
	viewer.getControl().setRedraw(true);
	}
	});
	}

	protected void sorterChanged() {
	final TableViewer viewer = getViewer();
	if (viewer == null) {
	return;
	}
	getSite().getShell().getDisplay().asyncExec(new Runnable() {
	public void run() {
	viewer.getControl().setRedraw(false);
	viewer.refresh(false);
	viewer.getControl().setRedraw(true);
	}
	});
	}

	protected abstract void handleKeyPressed(KeyEvent event);

	protected abstract void handleOpenEvent(OpenEvent event);

	/* (non-Javadoc)
	* @see org.eclipse.ui.part.ViewPart#saveState(org.eclipse.ui.IMemento)
	*/
	public void saveState(IMemento memento) {
	super.saveState(memento);

	//save column widths
	TableColumn[] columns = viewer.getTable().getColumns();
	for (int i = 0; i < columns.length; i++) {
	memento.putInteger(TAG_COLUMN_WIDTH + i, columns[i].getWidth());
	}

	saveSelection(memento);

	//save vertical position
	Scrollable scrollable = (Scrollable) viewer.getControl();
	ScrollBar bar = scrollable.getVerticalBar();
	int position = (bar != null) ? bar.getSelection() : 0;
	memento.putInteger(TAG_VERTICAL_POSITION, position);
	//save horizontal position
	bar = scrollable.getHorizontalBar();
	position = (bar != null) ? bar.getSelection() : 0;
	memento.putInteger(TAG_HORIZONTAL_POSITION, position);
	}

	protected abstract void saveSelection(IMemento memento);

	private void restoreColumnWidths(IMemento memento) {
	if (memento == null) {
	return;
	}
	columnLayouts = new ColumnLayoutData[getFields().length];
	for (int i = 0; i < columnLayouts.length; i++) {
	Integer width = memento.getInteger(TAG_COLUMN_WIDTH + i);
	if (width == null) {
	columnLayouts = null;
	break;
	}
	else {
	columnLayouts[i] = new ColumnPixelData(width.intValue(), true);
	}
	}
	}

	protected abstract IStructuredSelection restoreSelection(IMemento memento);

	private int restoreVerticalScrollBarPosition(IMemento memento) {
	if (memento == null) {
	return 0;
	}
	Integer position = memento.getInteger(TAG_VERTICAL_POSITION);
	return (position == null) ? 0 : position.intValue();
	}

	private int restoreHorizontalScrollBarPosition(IMemento memento) {
	if (memento == null) {
	return 0;
	}
	Integer position = memento.getInteger(TAG_HORIZONTAL_POSITION);
	return (position == null) ? 0 : position.intValue();
	}

	}