[cairo] Clipping and stroking

[Bill Spitzak]

Carl Worth wrote:

>>Therefore it may make sense to return the extents as coordinates so this 
>>mistake is less likely.
> 
> 
> Perhaps. Would we then also want to change cairo_rectangle to take a
> pair of coordinates? (Which, admittedly, would feel somewhat awkward
> to me).

I would leave it as-is using width+height since it already is that way 
and it makes drawing small squares easier and everybody is used to it. 
Also if you accidentally send two corners the mistake is obvious, as 
opposed to the rounding mistake above.