[cairo] Problems with cairo PDF generation and Mac OS X PDF rendering

[Ryan Schmidt]

Hi again. Graphviz [1] with cairo/pango support now has the ability  
to generate PDFs for the first time, but the result is weird, in the  
following way: The PDF looks fine in Adobe Reader 7.0.8 (the latest),  
and also in Adobe Acrobat Reader 5.0.5 (almost 5 years old), but it  
looks wrong in Mac OS X 10.4.7's Preview.app 3.0.7. The PDF, and PNGs  
of how it looks in Adobe Reader and Preview, are attached.

I first asked [2] on the graphviz-devel mailing list (where the  
attachments are also available, in case they don't come through on  
this list) and John Ellson, one of the Graphviz developers, suggested  
I ask here:

> It looks like the viewer is having difficulty with the curve-to  
> segments of paths.
> I would guess that if you use shape=box for the nodes that they  
> would then show up ?
> Probably the cairo list is the place to ask first, unless there is  
> an active list for the viewer?

I tried using box-shaped nodes instead of ovals, as he suggested, but  
it made no difference; the PDF still shows up great in Adobe Reader,  
and the node and edge lines are still not shown in Preview.

Preview.app isn't rendering the PDFs; a core Mac OS X library is.  
(The same display anomalies are present when viewing the PDF attached  
to this mail in Mail.app, for example.) If this turns out to be a bug  
in that Mac OS X PDF rendering library, I'll be happy to submit a bug  
report to Apple. But the likely effect of this will be that either  
the bug will be ignored for 3 years, then closed as out-of-date, or  
that the issue will be dealt with after a few months but the fix only  
made available in the next non-free Mac OS X update. Which is why I'm  
asking here first, since if this turns out to be a bug in the way  
cairo generates its PDFs, then I imagine the cairo developers would  
be able to react much quicker than this. :-)



[1] http://www.graphviz.org/

[2] https://mailman.research.att.com/pipermail/graphviz-devel/ 
2006/000214.html

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