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scroll an image (flicker free, no double buffering)
/*
* Canvas example snippet: scroll an image (flicker free, no double buffering)
*
* For a list of all SWT example snippets see
* http://dev.eclipse.org/viewcvs/index.cgi/%7Echeckout%7E/platform-swt-home/dev.html#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.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 Snippet48 {
public static void main(String[] args) {
Display display = new Display();
final Shell shell = new Shell(display, SWT.SHELL_TRIM
| SWT.NO_BACKGROUND | SWT.NO_REDRAW_RESIZE | SWT.V_SCROLL
| SWT.H_SCROLL);
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 ScrollBar hBar = shell.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();
shell.scroll(destX, 0, 0, 0, rect.width, rect.height, false);
origin.x = -hSelection;
}
});
final ScrollBar vBar = shell.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();
shell.scroll(0, destY, 0, 0, rect.width, rect.height, false);
origin.y = -vSelection;
}
});
shell.addListener(SWT.Resize, new Listener() {
public void handleEvent(Event e) {
Rectangle rect = image.getBounds();
Rectangle client = shell.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;
}
shell.redraw();
}
});
shell.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 = shell.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();
}
display.dispose();
}
}
