import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class PolylineBug {

	public static void main(String[] args) {

		final Display display = new Display();
		final Shell shell = new Shell(display);
		shell.addPaintListener(new PaintListener() {
			public void paintControl(PaintEvent event) {
				Rectangle rect = shell.getClientArea();
				drawTwoLines(event.gc, rect);
			}
		});
		shell.setBounds(100, 100, 200, 200);
		shell.open();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch())
				display.sleep();
		}
		display.dispose();
	}

	protected static void drawTwoLines(GC gc, Rectangle rect) {
		// With advanced set to true performance is better and the machine
		// does not lock up while the lines are being drawn.
		gc.setAdvanced(false);
		
		int[] points = new int[rect.width * 8];
		int[] points2 = new int[rect.width * 8];
		int maxy = rect.height - 1;
		int miny = 0;

		// Create a line which zig-zags between min and max y.
		for (int i = 0; i < points.length - 3; i += 4) {
			int x = i / 8;
			points[i] = x;
			points[i + 1] = miny;
			points[i + 2] = x + 1;
			points[i + 3] = maxy;
			// Create the other line going the other way.
			points2[i] = x;
			points2[i + 1] = maxy;
			points2[i + 2] = x + 1;
			points2[i + 3] = miny;
		}
		int style = gc.getLineStyle();
		Color color = gc.getForeground();
		Color blue = new Color(gc.getDevice(), 0, 0, 128);
		Color green = new Color(gc.getDevice(), 0, 128, 0);

		long startTime = System.currentTimeMillis();
		long endTime;

		System.err
				.println("If setAdvanced is false the machine may be non-responsive while the styled lines are drawn.");
		System.err
				.println("The effect is more noticeable the larger the window is.");
		System.err
				.println("Try moving the mouse around while the image is being drawn on a maximised window.");

		// If the line style is SWT.SOLID there is no problem.
		gc.setLineStyle(SWT.LINE_DASH);
		gc.setForeground(blue);
		gc.drawPolyline(points);
		endTime = System.currentTimeMillis();
		System.err.println("First line complete.");
		System.err.println("First line took " + (endTime - startTime)
				+ " milliseconds with " + (points.length / 2)
				+ " points and gc.setAdvanced(" + gc.getAdvanced() + ")");
		startTime = System.currentTimeMillis();
		gc.setLineStyle(SWT.LINE_DOT);
		gc.setForeground(green);
		gc.drawPolyline(points2);
		endTime = System.currentTimeMillis();
		System.err.println("Second line complete.");
		System.err.println("Second line took " + (endTime - startTime)
				+ " milliseconds with " + (points.length / 2)
				+ " points and gc.setAdvanced(" + gc.getAdvanced() + ")");

		blue.dispose();
		green.dispose();

		gc.setLineStyle(style);
		gc.setForeground(color);

	}

}