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

Owen Taylor otaylor at redhat.com
Tue Oct 19 10:29:20 PDT 2004

On Tue, 2004-10-19 at 12:43 -0400, Jon Smirl wrote:
> On Tue, 19 Oct 2004 12:11:54 -0400, Carl Worth <cworth at cworth.org> wrote:
> > Not unless I'm misunderstanding you. The 0.5 positioning just comes from
> > the simple fact that the stroked path extends on both sides of the
> > path. Therefore, to light up a single row of pixels, a path of width 1.0
> > must be centered within those pixels[*]. But any particular pixel can be
> > lit up in this fashion.
> 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.

It should be noted that early versions of Java2D tried magically
adjusting stroked lines by 0.5 pixels, and this was later deprecated and
backed out. 

I think you easily get on the wrong side of the balance between making
Cairo magically "do the right thing" and making it simply, reliably,
and reproducibly do the right thing.


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