Re: A Question

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The above answers are being a bit complex.

The real answer is: Cairo is absolutely designed so that non-integer line
widths and/or line positions work.

It will attempt to simulate the result as best it can using anti-aliasing
(ie drawing some pixels not fully opaque).

The complexity in the answer is due to two things: 1. this is impossible to
do perfectly if intermediate data only consists of one value for each
pixel. 2: there are bugs and/or sub-optimal implementations in Cairo.



On Tue, Feb 26, 2019 at 9:41 AM Bryce Harrington <[email protected]>
wrote:

> On Fri, Feb 22, 2019 at 04:59:43PM -0800, Thomas Dineen wrote:
> > Gentle People:
> >
> >    A question on Cairo: The X Y inputs to Cairo drawing functions are
> type
> > double.
> >
> > Dose this imply that pixel or line spacing could be less than 1.0?
> >
> > Could the spacing be say 0.5 or 0.25?
>
> Cairo does track the decimal positioning, although beware there is some
> culling behavior that can kick in when you're < 1.0, that could make
> things disappear unexpectedly.  I don't think the documentation goes
> into the culling rules in much depth, and there may be some
> inconsistencies in how it's handled so may be down to experimentation
> and/or code study.
>
> There's a FAQ item that's about a slightly different issue but might be
> of interest:
>
>   https://www.cairographics.org/FAQ/#sharp_lines
>
> HTH,
> Bryce
> --
> cairo mailing list
> [email protected]
> https://lists.cairographics.org/mailman/listinfo/cairo

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<div dir=3D"ltr">The above answers are being a bit complex.<div><br></div><=
div>The real answer is: Cairo is absolutely designed so that non-integer li=
ne widths and/or line positions work.</div><div><br></div><div>It will atte=
mpt to simulate the result as best it can using anti-aliasing (ie drawing s=
ome pixels not fully opaque).</div><div><br></div><div>The complexity in th=
e answer is due to two things: 1. this is impossible to do perfectly if int=
ermediate data only consists of one value for each pixel. 2: there are bugs=
 and/or sub-optimal implementations in Cairo.</div><div><br></div><div><br>=
</div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_=
attr">On Tue, Feb 26, 2019 at 9:41 AM Bryce Harrington &lt;<a href=3D"mailt=
o:[email protected]">[email protected]</a>&gt; wrote:<br></=
div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;bor=
der-left:1px solid rgb(204,204,204);padding-left:1ex">On Fri, Feb 22, 2019 =
at 04:59:43PM -0800, Thomas Dineen wrote:<br>
&gt; Gentle People:<br>
&gt; <br>
&gt; =C2=A0=C2=A0 A question on Cairo: The X Y inputs to Cairo drawing func=
tions are type<br>
&gt; double.<br>
&gt; <br>
&gt; Dose this imply that pixel or line spacing could be less than 1.0?<br>
&gt; <br>
&gt; Could the spacing be say 0.5 or 0.25?<br>
<br>
Cairo does track the decimal positioning, although beware there is some<br>
culling behavior that can kick in when you&#39;re &lt; 1.0, that could make=
<br>
things disappear unexpectedly.=C2=A0 I don&#39;t think the documentation go=
es<br>
into the culling rules in much depth, and there may be some<br>
inconsistencies in how it&#39;s handled so may be down to experimentation<b=
r>
and/or code study.<br>
<br>
There&#39;s a FAQ item that&#39;s about a slightly different issue but migh=
t be<br>
of interest:<br>
<br>
=C2=A0 <a href=3D"https://www.cairographics.org/FAQ/#sharp_lines" rel=3D"no=
referrer" target=3D"_blank">https://www.cairographics.org/FAQ/#sharp_lines<=
/a><br>
<br>
HTH,<br>
Bryce<br>
-- <br>
cairo mailing list<br>
<a href=3D"mailto:[email protected]" target=3D"_blank">cairo@cairogra=
phics.org</a><br>
<a href=3D"https://lists.cairographics.org/mailman/listinfo/cairo" rel=3D"n=
oreferrer" target=3D"_blank">https://lists.cairographics.org/mailman/listin=
fo/cairo</a></blockquote></div>

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