[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.

Regards,
							Owen

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