[cairo] Antialiasing and round, bevelled widgets (was: Cairo developers conference call...)

Keith Packard keithp at keithp.com
Tue Oct 19 09:46:21 PDT 2004


Around 12 o'clock on Oct 19, Jon Smirl wrote:

> Given this logic, should the entire drawing grid be offset 0.5 pixels
> with a global transform? Then a normal user wouldn't see this. Fonts
> would need to be backed up 0.5 since they assume 0.0 is the top of the
> pixel.

With that transform, fills are 'off by 0.5'.  It's the age-old problem 
with centering strokes along the path, you either get pixel-aligned fills 
or pixel-aligned odd-width strokes, but you can't ever have both.  That's 
one of the reasons cairo uses a default line with of 2 units (the other 
being that 2 pixels looks a lot nicer on the screen than 1 pixel).

-keith


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