ImageScrollFlickerFree.java Source code

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Here is the source code for ImageScrollFlickerFree.java

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/*******************************************************************************
 * Copyright (c) 2000, 2004 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
 *******************************************************************************/

/*
 * Canvas example snippet: scroll an image (flicker free, no double buffering)
 *
 * For a list of all SWT example snippets see
 * http://www.eclipse.org/swt/snippets/
 */
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.FileDialog;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.ScrollBar;
import org.eclipse.swt.widgets.Shell;

public class ImageScrollFlickerFree {

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());
        Image originalImage = null;
        FileDialog dialog = new FileDialog(shell, SWT.OPEN);
        dialog.setText("Open an image file or cancel");
        String string = dialog.open();
        if (string != null) {
            originalImage = new Image(display, string);
        }
        if (originalImage == null) {
            int width = 150, height = 200;
            originalImage = new Image(display, width, height);
            GC gc = new GC(originalImage);
            gc.fillRectangle(0, 0, width, height);
            gc.drawLine(0, 0, width, height);
            gc.drawLine(0, height, width, 0);
            gc.drawText("Default Image", 10, 10);
            gc.dispose();
        }
        final Image image = originalImage;
        final Point origin = new Point(0, 0);
        final Canvas canvas = new Canvas(shell,
                SWT.NO_BACKGROUND | SWT.NO_REDRAW_RESIZE | SWT.V_SCROLL | SWT.H_SCROLL);
        final ScrollBar hBar = canvas.getHorizontalBar();
        hBar.addListener(SWT.Selection, new Listener() {
            public void handleEvent(Event e) {
                int hSelection = hBar.getSelection();
                int destX = -hSelection - origin.x;
                Rectangle rect = image.getBounds();
                canvas.scroll(destX, 0, 0, 0, rect.width, rect.height, false);
                origin.x = -hSelection;
            }
        });
        final ScrollBar vBar = canvas.getVerticalBar();
        vBar.addListener(SWT.Selection, new Listener() {
            public void handleEvent(Event e) {
                int vSelection = vBar.getSelection();
                int destY = -vSelection - origin.y;
                Rectangle rect = image.getBounds();
                canvas.scroll(0, destY, 0, 0, rect.width, rect.height, false);
                origin.y = -vSelection;
            }
        });
        canvas.addListener(SWT.Resize, new Listener() {
            public void handleEvent(Event e) {
                Rectangle rect = image.getBounds();
                Rectangle client = canvas.getClientArea();
                hBar.setMaximum(rect.width);
                vBar.setMaximum(rect.height);
                hBar.setThumb(Math.min(rect.width, client.width));
                vBar.setThumb(Math.min(rect.height, client.height));
                int hPage = rect.width - client.width;
                int vPage = rect.height - client.height;
                int hSelection = hBar.getSelection();
                int vSelection = vBar.getSelection();
                if (hSelection >= hPage) {
                    if (hPage <= 0)
                        hSelection = 0;
                    origin.x = -hSelection;
                }
                if (vSelection >= vPage) {
                    if (vPage <= 0)
                        vSelection = 0;
                    origin.y = -vSelection;
                }
                canvas.redraw();
            }
        });
        canvas.addListener(SWT.Paint, new Listener() {
            public void handleEvent(Event e) {
                GC gc = e.gc;
                gc.drawImage(image, origin.x, origin.y);
                Rectangle rect = image.getBounds();
                Rectangle client = canvas.getClientArea();
                int marginWidth = client.width - rect.width;
                if (marginWidth > 0) {
                    gc.fillRectangle(rect.width, 0, marginWidth, client.height);
                }
                int marginHeight = client.height - rect.height;
                if (marginHeight > 0) {
                    gc.fillRectangle(0, rect.height, client.width, marginHeight);
                }
            }
        });
        shell.setSize(200, 150);
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }
        originalImage.dispose();
        display.dispose();
    }

}