[cairo] antialiasing pixel alignment for applications

[Bill Spitzak]

This has come up and is being talked about right now. The subject is 
"Using ADD operator to prevent..."

Robert O'Callahan wrote:
> Sorry if this is off-topic or has come up before or is just my own ignorance...
> 
> Suppose I have two adjacent rectangles with pixel coordinates
> (0,0,10,10.5) and (0,10.5,10,20). If I fill them on a non-antialiased
> device and I do my rounding correctly it's easy to ensure I get a
> solid (0,0,10,20) rectangle. If I do antialiased fills based on
> coverage I'm going to get one row of pixels that's not solid. What do
> you recommend applications do to deal with this sort of thing?
> 
> Rob