proper way to get cairo font width

[Tommi Sakari Uimonen <tuimonen cc hut fi>]

Hello. What is the best way to query font width from cairo, in case that I 
want to set size_hint for the widget that is drawing with that font?

Currently I'm creating a cairo for some existing widget and set there the 
desired font and query the width from text_extents_t struct, but it seems 
a bit hackish.

Tommi