如何在SWT ScrollBar上设置滚动条滑块的最小尺寸？

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.ScrollBar;
import org.eclipse.swt.widgets.Shell;

public class ScrollBarExample {
    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());

        // 创建一个垂直滚动条
        ScrollBar scrollBar = new ScrollBar(shell, SWT.VERTICAL);

        // 设置滑块的最小尺寸为20
        scrollBar.setThumb(20);

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