[cairo] Different output between Linux and Mac

[Neil Mayhew]

Forgot the attachments... sorry.

On 18/03/09 03:48 PM Neil Mayhew wrote:
> On 15/03/09 11:19 PM Neil Mayhew wrote:
>> Am I correct in thinking that I should get identical SVG output on 
>> the different platforms?
>
> I didn't get any feedback about this question...
>
>> I can send sample output and code if desired.
>
> ... so I'm sending some files. Attached are the SVGs from Mac and 
> Linux. There's just two very slight differences, which aren't easily 
> to spot in a regular line-oriented diff. You need to look at them in 
> meld (Linux) or TextWrangler's diff (Mac) to see the difference. For 
> example, on line 9 Mac has 0.834007 and Linux has 0.834694.
>
> I'm also sending the output of cairo-trace --no-callbacks. I couldn't 
> build it on Mac (you knew this, right?) , because it depends on ELF 
> for the callbacks. However, I built it on Linux from git, and ran it 
> with the system cairo libraries. Based on my own tracing, I believe 
> the output on Mac would be identical if it were possible.
>
> Interestingly, some of the coordinates in the SVGs don't agree with 
> what's in the trace. In the first stroked path, for example, the SVG 
> has "M 0 0.000341478" but the trace has "0 0 m" (which corresponds to 
> what I had in my code). However, the 87.971302 that follows almost 
> immediately agrees exactly. Then there's a disagreement over 75.779717 
> vs 75.779804, but agreement on -12.971302. It looks like there's some 
> sort of rounding error going on, but not in every case.
>
> I know these differences may seem very small, but they make regression 
> testing almost impossible.
>
> --Neil
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