[cairo] PATCH cairo-www: Simpler explanation for how to get sharp, single-pixel-wide lines

[Stefan Salewski]

On Wed, 2017-05-17 at 21:24 +1200, Lawrence D'Oliveiro wrote:
> Note that it only discusses “horizontal/vertical” lines. This is the
> specific situation where turning off antialiasing is the simplest
> solution.

Maybe the simplest, but not a good one.

I had that problem in my application

http://ssalewski.de/PetEd.html.en

I needed/wanted sharp lines. Turning off antialiasing gave not the
desired results, so I had to follow indeed the tutorial. I was not too
happy about that, because the app was coded in Ruby, and that rounding
to exact positions costs some CPU cycles. I can not remember details, I
think I asked at cairo mailing list that time. At least that proposed
solution worked fine. But I would like to see some direct cairo support
for that, maybe a drawing mode which does that rounding internally. I
think I was thinking about to make a C routine for Ruby for that, but
never did it. Well, now we have faster languages than Ruby or Python
available, like Nim, Rust and many more, so it is not a big problem any
more. And with current HiDPI monitors we may not need antialiasing at
all any more. I have recently turned of antialiasing for font rendering
 on my Gnome desctop -- was not bad, I liked the sharper fonts.
Unfortunately it worked not that well for some font sizes and some web
pages, so I turned on aliasing again for now.