How to set the size of a combo box?

[Lars Paulsen <lars_paulsen web de>]

Hello All,

I have created a combo box and it is nicely displayed in my window.
But it always takes the full window size.

I would like to limit the size in that way, that it always takes 1 row 
height
or better say the height of the text line or font size (1em in CSS 
encoding).

I have only text in the combo box so it is not useful that it spans 
several lines.
Thanks for all help in advance.

Best Regards,
Lars