[news.eclipse.platform.swt] Re: Draw outside clip

[Michael Szediwy <michael@xxxxxxxxxx>]

Here is an example:

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Slider;

public class Test {

	private Slider slider;

	private Canvas canvas;

	private class MyPaintListener implements PaintListener {

		public void paintControl (PaintEvent e) {
			Point center= canvas.getSize();
			int scale= 100;
			long now= System.currentTimeMillis();
			int val= slider.getSelection();
			val*= val;
			e.gc.setLineWidth(3);
			e.gc.setLineStyle(SWT.LINE_DOT);
			e.gc.drawLine(center.x / 2 - scale * val, center.y / 2 + scale * val,
				center.x / 2 + scale * val, center.y / 2 - scale * val);
			System.out.println("Took " + (System.currentTimeMillis() - now) + ", "
				+ (scale * val));

		}

	};
	
	public void createControl (Composite parent) {
		GridData gridData1= new GridData();
		gridData1.horizontalAlignment= GridData.FILL;
		gridData1.grabExcessHorizontalSpace= true;
		gridData1.verticalAlignment= GridData.CENTER;

		createCanvas(parent);

		parent.setLayout(new GridLayout());
		slider= new Slider(parent, SWT.NONE);
		slider.setLayoutData(gridData1);
		slider.addSelectionListener(new SelectionListener() {

			public void widgetDefaultSelected (SelectionEvent e) {
				System.out.println("there");

			}

			public void widgetSelected (SelectionEvent e) {
				System.out.println("hi " + slider.getSelection());
				canvas.redraw();
				canvas.redraw();
				canvas.redraw();
				canvas.redraw();
				canvas.redraw();

			}
		});
	}

	private void createCanvas (Composite parent) {
		GridData gridData= new GridData();
		gridData.horizontalAlignment= GridData.FILL;
		gridData.grabExcessHorizontalSpace= true;
		gridData.grabExcessVerticalSpace= true;
		gridData.verticalAlignment= GridData.FILL;
		canvas= new Canvas(parent, SWT.NONE);
		canvas.setLayoutData(gridData);
		canvas.addPaintListener(new MyPaintListener());
	}

	public static void main (String[] args) {
		Display display= new Display();
		Shell shell= new Shell(display);
		shell.setSize(500, 400);
		shell.setLayout(new GridLayout());

		Test test= new Test();
		test.createControl(shell);

		shell.open();

		while (!shell.isDisposed()) {
			if (!display.readAndDispatch())
				display.sleep();
		}
	}
}


Michael Szediwy wrote:
> Hi,
>
> this is a stupid question, maybe. If I draw a polyline on a canvas with 
> a certain size (maybe 50000 pixel) whose points lie outside the
> clipping area the whole application begins to hang. I'm testing on a
> Windows XP machine.
>
> Is anything known about such problems?
>
> Cheers
>
> Michael