Double Buffer
/*******************************************************************************
* All Right Reserved. Copyright (c) 1998, 2004 Jackwind Li Guojie
*
* Created on 2004-4-18 16:12:14 by JACK $Id$
*
******************************************************************************/
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
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.Shell;
public class DoubleBuffer {
Display display = new Display();
Shell shell = new Shell(display);
public DoubleBuffer() {
shell.setLayout(new FillLayout());
final Image imageEclipse = new Image(display, "java2s.gif");
// final Canvas canvas = new Canvas(shell, SWT.NULL);
// canvas.addPaintListener(new PaintListener() {
// public void paintControl(PaintEvent e) {
// Point size = canvas.getSize();
//
// int x1 = (int) (Math.random() * size.x);
// int y1 = (int) (Math.random() * size.y);
// int x2 = Math.max(canvas.getBounds().width - x1 - 10, 50);
// int y2 = Math.max(canvas.getBounds().height - y1 - 10, 50);
//
//
// e.gc.drawRoundRectangle(x1, y1, x2, y2, 5, 5);
//
// display.timerExec(100, new Runnable() {
// public void run() {
// canvas.redraw();
// }
// });
//
// }
// });
final Canvas doubleBufferedCanvas = new Canvas(shell, SWT.NO_BACKGROUND);
doubleBufferedCanvas.addPaintListener(new PaintListener() {
public void paintControl(PaintEvent e) {
// Creates new image only absolutely necessary.
Image image = (Image) doubleBufferedCanvas.getData("double-buffer-image");
if (image == null
|| image.getBounds().width != doubleBufferedCanvas.getSize().x
|| image.getBounds().height != doubleBufferedCanvas.getSize().y) {
image =
new Image(
display,
doubleBufferedCanvas.getSize().x,
doubleBufferedCanvas.getSize().y);
doubleBufferedCanvas.setData("double-buffer-image", image);
}
// Initializes the graphics context of the image.
GC imageGC = new GC(image);
imageGC.setBackground(e.gc.getBackground());
imageGC.setForeground(e.gc.getForeground());
imageGC.setFont(e.gc.getFont());
// Fills background.
Rectangle imageSize = image.getBounds();
imageGC.fillRectangle(0, 0, imageSize.width + 1, imageSize.height + 1);
// Performs actual drawing here ...
Point size = doubleBufferedCanvas.getSize();
int x1 = (int) (Math.random() * size.x);
int y1 = (int) (Math.random() * size.y);
int x2 = Math.max(doubleBufferedCanvas.getBounds().width - x1 - 10, 50);
int y2 = Math.max(doubleBufferedCanvas.getBounds().height - y1 - 10, 50);
imageGC.drawRoundRectangle(x1, y1, x2, y2, 5, 5);
// Draws the buffer image onto the canvas.
e.gc.drawImage(image, 0, 0);
imageGC.dispose();
display.timerExec(100, new Runnable() {
public void run() {
doubleBufferedCanvas.redraw();
}
});
}
});
shell.setSize(300, 200);
shell.open();
//textUser.forceFocus();
// Set up the event loop.
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
// If no more entries in event queue
display.sleep();
}
}
display.dispose();
}
/**
* Equips the specified canvas with double buffering to reduce flicker.
*
* @param canvas
*/
public static void enableDoubleBuffer(Canvas canvas) {
}
public static void main(String[] args) {
new DoubleBuffer();
}
}
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