package eclipsecookbook;

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Region;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;


public class NonRectanglegularClass {

    
    public static void main(String[] args) {
        final Display display = new Display();
        final Shell shell = new Shell(display, SWT.NO_TRIM);
        Region region = new Region();
        region.add(createCircle(50, 50, 50));
        region.subtract(createCircle(50, 50, 20));
        shell.setRegion(region);
        shell.setSize(region.getBounds().width, region.getBounds().height);
        shell.setBackground(display.getSystemColor(SWT.COLOR_BLUE));
        Button button = new Button(shell, SWT.PUSH);
        button.setText("Exit");
        button.setBounds(35, 6, 35, 20);
        button.addListener(SWT.Selection, new Listener() {

            @Override
            public void handleEvent(Event arg0) {
                shell.close();
            }
        });
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();

    }

    static int[] createCircle(int xOffset, int yOffset, int radius) {
        int[] circlePoints = new int[10 * radius];
        for (int loopIndex = 0; loopIndex < 2* radius + 1; loopIndex++) {
            int xCurrent = loopIndex - radius;
            int yCurrent = (int) Math.sqrt(radius * radius - xCurrent
                    * xCurrent);
            int doubleLoopIndex = 2 * loopIndex;
            circlePoints[doubleLoopIndex] = xCurrent + xOffset;
            circlePoints[doubleLoopIndex + 1] = yCurrent + yOffset;
            circlePoints[10 * radius - doubleLoopIndex - 2] = xCurrent
                    + xOffset;
            circlePoints[10 * radius - doubleLoopIndex - 1] = -yCurrent
                    + yOffset;
        }
        return circlePoints;
    }
}