How to set height of SWT List in rows?

Question

I have a class based on Composite that embeds an SWT List instance. Using the default settings, the list is five rows high on my WinXP system. Without relying on hard-coded pixel values or DPI settings and the like, how can I set the height of the list (and the surrounding composite) to a fixed number of rows, say 3, without any added inner margins?

public FileSetBox(Composite parent, int style)
{
    super(parent, style);

    setLayout(new FillLayout());

    this.list = new List(this, SWT.V_SCROLL);

    ...
}

Update:

The following works, but it does not take into account the height added by the border, which results in parts of the last line being covered. Any ideas how to calculate this, too?

public FileSetBox(Composite parent, int style)
{
    ...
    GC gc = new GC(this);
    gc.setFont(this.list.getFont());
    this.preferredHeight = gc.getFontMetrics().getHeight() * 3;
    gc.dispose();
    ...
}

@Override
public Point computeSize(int arg0, int arg1)
{
    Point size = super.computeSize(arg0, arg1);
    return new Point(size.x, this.preferredHeight);
}

Answer 1

Can't you use list.getBorderWidth() and list.getItemHeight() to get the height?

Answer 2

public FileSetBox(Composite parent, int style)
{
    super(parent, style);

    setLayout(new GridLayout(1, false));

    this.list = new List(this, SWT.V_SCROLL);

    GridData data = new GridData(GridData.FILL_BOTH);
    data.heightHint = 10 * ((List)control).getItemHeight(); // height for 10 rows
    data.widthHint = getStringWidth(25, list); // width enough to display 25 chars
    list.setLayoutData(data);

    ...
}

    public static int getStringWidth(int nChars, Control control){
        GC gc = new GC(control);
        gc.setFont(control.getFont());
        FontMetrics fontMetrics = gc.getFontMetrics();
        gc.dispose();
        return nChars * fontMetrics.getAverageCharWidth();
    }