import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class MouseWheelTest {

    private static int pos;

    public static void main(String[] args) {
        final Display display = new Display();

        final Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());

        final Composite composite = new Composite(shell, 0);
        composite.addListener(SWT.MouseWheel, event -> {
            pos += event.count;
            System.out.println("event.count = " + event.count);
            composite.redraw();
        });
        composite.addListener(SWT.Paint, event -> {
            final Point size = composite.getSize();
            final int height = event.gc.getFontMetrics().getHeight();
            int i = pos;
            for (int y = 0; y < size.y; y += height) {
                event.gc.drawString(String.valueOf(i++), 0, y);
            }
        });

        shell.setSize(400, 300);
        shell.open();

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

        display.dispose();
    }
}