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

Carl Worth cworth at cworth.org
Tue Oct 19 10:32:28 PDT 2004

On Tue, 19 Oct 2004 12:57:22 -0400, Jon Smirl wrote:
> Won't apps that fix this by adding 0.5 pixel look wrong when drawn at
> a larger scale?

They won't look "wrong", as the 0.5 unit adjust is perfectly justifiable
geometrically. For example, shifting a stroke inward one half the stroke
width will make the outer edge of the stroke align precisely with the
boundary of the fill from the original path.

But, at a different scale, the result will not necessarily have the
same device-pixel alignment that is the reason for the adjustment here.

So, the adjustment necessary for aligning to device pixels is
transformation-dependent, shape-dependent, and perhaps
scene-dependent. It's the dependency on the shape and the scene that
have pushed me toward making applications deal with this. But getting it
right for all transformations is not easy. So I'm now wanting to put
some support into cairo to deal with this, but also provide a means for
the user to provide some shape-specific hints.


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