org.eclipse.swt.custom.BusyIndicator.java Source code

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Here is the source code for org.eclipse.swt.custom.BusyIndicator.java

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/*******************************************************************************
 * Copyright (c) 2000, 2011 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.custom;

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

/**
 * Support for showing a Busy Cursor during a long running process.
 *
 * @see <a href="http://www.eclipse.org/swt/snippets/#busyindicator">BusyIndicator snippets</a>
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 */
public class BusyIndicator {

    static int nextBusyId = 1;
    static final String BUSYID_NAME = "SWT BusyIndicator"; //$NON-NLS-1$
    static final String BUSY_CURSOR = "SWT BusyIndicator Cursor"; //$NON-NLS-1$

    /**
     * Runs the given <code>Runnable</code> while providing
     * busy feedback using this busy indicator.
     *
     * @param display the display on which the busy feedback should be
     *        displayed.  If the display is null, the Display for the current
     *        thread will be used.  If there is no Display for the current thread,
     *        the runnable code will be executed and no busy feedback will be displayed.
     * @param runnable the runnable for which busy feedback is to be shown.
     *        Must not be null.
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the runnable is null</li>
     * </ul>
     */

    public static void showWhile(Display display, Runnable runnable) {
        if (runnable == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        if (display == null) {
            display = Display.getCurrent();
            if (display == null) {
                runnable.run();
                return;
            }
        }

        Integer busyId = Integer.valueOf(nextBusyId);
        nextBusyId++;
        Cursor cursor = display.getSystemCursor(SWT.CURSOR_WAIT);
        Shell[] shells = display.getShells();
        for (Shell shell : shells) {
            Integer id = (Integer) shell.getData(BUSYID_NAME);
            if (id == null) {
                setCursorAndId(shell, cursor, busyId);
            }
        }

        try {
            runnable.run();
        } finally {
            shells = display.getShells();
            for (Shell shell : shells) {
                Integer id = (Integer) shell.getData(BUSYID_NAME);
                if (id == busyId) {
                    setCursorAndId(shell, null, null);
                }
            }
        }
    }

    /**
     * Paranoia code to make sure we don't break UI because of one shell disposed, see bug 532632 comment 20
     */
    private static void setCursorAndId(Shell shell, Cursor cursor, Integer busyId) {
        if (!shell.isDisposed()) {
            shell.setCursor(cursor);
        }
        if (!shell.isDisposed()) {
            shell.setData(BUSYID_NAME, busyId);
        }
    }
}