I tried various ways, I googled a lot, but I was unable to change the font of the text on a button (TextButton). I use UiBinder, but I don't think it is relevant.
I use <set-configuration-property name="CssResource.style" value="pretty"/> to see the class names, but I have hard time to find out which part of the class is relevant.

BTW, the above property has a strange effect on sub-menus: the whole sprite is displayed instead of just the arrow. Try it! I suppose there is a kind of CSS name collision in this mode, event though they are still obfuscated.

If I set the the value to "stable-notype", the button gets funny because of class clashes. But I can see that I can change the font by setting the property on .button .text. And it works on this mode. But in normal, obfuscated mode, this gets lost. How to make CSS selectors surviving the obfuscation phase?
Did I miss some styling guide somewhere?

I hope I don't have to make a whole theme to achieve this task. Even less as I want this change only on one button, on one page (the login).