org.csstudio.apputil.ui.swt.CheckBoxImages.java Source code

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Here is the source code for org.csstudio.apputil.ui.swt.CheckBoxImages.java

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/*******************************************************************************
 * Copyright (c) 2010 Oak Ridge National Laboratory.
 * 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
 ******************************************************************************/
package org.csstudio.apputil.ui.swt;

import org.csstudio.apputil.ui.Activator;
import org.csstudio.utility.singlesource.SingleSourcePlugin;
import org.eclipse.jface.resource.ImageRegistry;
import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Shell;

/** Get a snapshot of the native checkbox control images.
 *  <p>
 *  While SWING makes it easy to include checkboxes or any
 *  other controls in a table, SWT isn't there (yet?).
 *  So one has to display the image of a checkbox.
 *  <p>
 *  There are two ways to get checkbox images:
 *  Use fixed images, which will always work,
 *  or use a hack from
 *  <code>
 *  feed://tom-eclipse-dev.blogspot.com/feeds/46160309661596839/comments/default
 *  </code>
 *  to take a snapshot of the 'real' button from a briefly displayed shell.
 *  That looks more like the native check boxes of the OS,
 *  but sometimes fails, maybe related to the briefly displayed shell
 *  being covered by another window by accident.
 *
 *  @author Kay Kasemir
 */
@SuppressWarnings("nls")
public class CheckBoxImages {
    /** Set <code>true</code> to use fixed images, otherwise use the hack */
    final private static boolean use_fixed_images = true;

    private static final String CHECKED_KEY = "CHECKED";
    private static final String UNCHECK_KEY = "UNCHECKED";
    private static CheckBoxImages instance = null;

    /** Singleton */
    private CheckBoxImages(final Control control) {
        final ImageRegistry registry = JFaceResources.getImageRegistry();
        if (registry.getDescriptor(CHECKED_KEY) != null)
            return;
        if (use_fixed_images) {
            registry.put(CHECKED_KEY, Activator.getImageDescriptor("icons/checked.gif"));
            registry.put(UNCHECK_KEY, Activator.getImageDescriptor("icons/unchecked.gif"));
        } else {
            registry.put(UNCHECK_KEY, makeShot(control, false));
            registry.put(CHECKED_KEY, makeShot(control, true));
        }
    }

    /** Create or obtain existing instance of CheckBoxImages
     *  @param control Any control, used to get background color etc.
     *  @return Singleton instance of CheckBoxImages
     */
    static public CheckBoxImages getInstance(final Control control) {
        if (instance == null)
            instance = new CheckBoxImages(control);
        return instance;
    }

    /** @return Image of selected or unselected button image */
    public Image getImage(final boolean selected) {
        return selected ? JFaceResources.getImageRegistry().get(CHECKED_KEY)
                : JFaceResources.getImageRegistry().get(UNCHECK_KEY);
    }

    /** @return Image that is snapshot of Checkbox control */
    private Image makeShot(final Control control, final boolean selected) {
        final Shell shell = new Shell(control.getShell(), SWT.NO_TRIM);

        // otherwise we have a default gray color
        final Color backgroundColor = control.getBackground();
        shell.setBackground(backgroundColor);

        final Button button = new Button(shell, SWT.CHECK);
        button.setBackground(backgroundColor);
        button.setSelection(selected);

        // Some tweaking that's a compromise between Win32, OSX, ...
        // versions of the actual control.
        final Point bsize = button.computeSize(SWT.DEFAULT, SWT.DEFAULT);
        // otherwise an image is stretched by width
        final int size = Math.max(bsize.x, bsize.y);
        button.setLocation(1, 1);
        button.setSize(size, size);
        shell.setSize(size, size);
        // Briefly display shell, take snapshot, close
        shell.open();
        // If switching windows during application startup,
        // the image would sometimes contain stuff from whatever
        // happened to be on top of the screen.
        // Maybe this helps to avoid that?
        shell.forceActive();
        final Image image = SingleSourcePlugin.getUIHelper().getScreenshot(shell.getDisplay(), button,
                new Rectangle(0, 0, size, size));
        shell.close();

        return image;
    }
}