Java SWT外壳-内部填充/边框

我有一个SWT外壳，它有一些我无法摆脱的未知填充物或边框。下面是我所说内容的截图。边界是绿色的。我怎样才能摆脱它，因为我的元素直接压在外壳的侧面看起来会更好

提前感谢：D

public static void main(String[] args) {
    Display display = new Display();
    Shell rootShell = new Shell(display);
    rootShell.setBackground(SWTGraphicUtil.getColorSafely(0, 255, 0));

    GridLayout rootLayout = new GridLayout();
    rootLayout.numColumns = 3;
    rootLayout.horizontalSpacing = 0;
    rootLayout.verticalSpacing = 0;
    rootLayout.marginTop = rootLayout.marginRight = rootLayout.marginBottom = rootLayout.marginLeft = 0;
    rootShell.setLayout(rootLayout);

    Label lbl = new Label(rootShell, SWT.NONE);
    lbl.setText("WHAT WHAT WHAT WHAT WHAT WHAT WHAT");
    lbl.setBackground(SWTGraphicUtil.getColorSafely(255, 0, 0));

    Label lbl2 = new Label(rootShell, SWT.NONE);
    lbl2.setText("WHAT WHAT WHAT WHAT WHAT WHAT WHAT");
    lbl2.setBackground(SWTGraphicUtil.getColorSafely(255, 0, 255));

    Label lbl3 = new Label(rootShell, SWT.NONE);
    lbl3.setText("WHAT WHAT WHAT WHAT WHAT WHAT WHAT");
    lbl3.setBackground(SWTGraphicUtil.getColorSafely(0, 0, 255));

    rootShell.pack();

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

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只需为

rootLayout

再设置两个变量：

rootLayout.marginWidth=0；
rootLayout.marginHeight=0；

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这应该去掉“填充”（实际上是一个边距；）。

新手犯了多大的错误。谢谢你的帮助！：D