DropDownList value selected by default?

Hi there,

I've got the following DropDownList, but it gets rendered with no options selected. How can I make ''one" the default option for this element?

var w, layout;


layout = "dialog {  \    dropdown: DropDownList { \        size: [100,20] \        properties: { \            items: ['one','two','three'] \        } \    } \
}";


w = new Window(layout);
w.show();

Thanks