org.eclipse.swt.snippets.Snippet275.java Source code

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Here is the source code for org.eclipse.swt.snippets.Snippet275.java

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/*******************************************************************************
 * Copyright (c) 2000, 2016 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.snippets;

/*
 * Canvas snippet: update a portion of a Canvas frequently
 *
 * For a list of all SWT example snippets see
 * http://www.eclipse.org/swt/snippets/
 */
import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

public class Snippet275 {

    static String value;

    public static void main(String[] args) {
        final int INTERVAL = 888;
        final Display display = new Display();
        final Image image = new Image(display, 750, 750);
        GC gc = new GC(image);
        gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
        gc.fillRectangle(image.getBounds());
        gc.dispose();

        Shell shell = new Shell(display);
        shell.setText("Snippet 275");
        shell.setBounds(10, 10, 790, 790);
        final Canvas canvas = new Canvas(shell, SWT.NONE);
        canvas.setBounds(10, 10, 750, 750);
        canvas.addListener(SWT.Paint, event -> {
            value = String.valueOf(System.currentTimeMillis());
            event.gc.drawImage(image, 0, 0);
            event.gc.drawString(value, 10, 10, true);
        });
        display.timerExec(INTERVAL, new Runnable() {
            @Override
            public void run() {
                if (canvas.isDisposed())
                    return;
                // canvas.redraw (); // <-- bad, damages more than is needed
                GC gc = new GC(canvas);
                Point extent = gc.stringExtent(value + '0');
                gc.dispose();
                canvas.redraw(10, 10, extent.x, extent.y, false);
                display.timerExec(INTERVAL, this);
            }
        });
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }
        image.dispose();
        display.dispose();
    }

}