[cairo] Different output between Linux and Mac

Neil Mayhew neil_mayhew at users.sourceforge.net
Wed Mar 18 14:48:08 PDT 2009

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.


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