[cairo] PDF Issue in OS X Preview

[Ken Treis]

Beautiful. That fixed it for me. Thanks Behdad!


Ken

On Oct 25, 2006, at 6:41 PM, Behdad Esfahbod wrote:

> On Wed, 2006-10-25 at 21:24 -0400, Behdad Esfahbod wrote:
>> On Wed, 2006-10-25 at 18:28 -0400, Ryan Schmidt wrote:
>>> On Oct 25, 2006, at 11:55, Ken Treis wrote:
>>>
>>>> I'm generating PDFs using the Ruby bindings and cairo-1.2.4.
>>>> Everything works fine for me until I try to set scaling. The
>>>> resulting PDF files look fine in Acrobat Reader but not in OS X
>>>> Preview.
>>>
>>> [snip]
>>>
>>> Thanks for writing. I too reported a problem with cairo-generated
>>> PDFs which looked fine in Adobe Reader but not OS X Preview. I'm not
>>> sure if your case is the same as the one I was seeing. My problem  
>>> was
>>> that my PDFs are generated by graphviz, and I was unsure if the
>>> problem was in cairo, graphviz, or Mac OS X's PDF renderer. Your
>>> message gives me hope that it might be a cairo problem after all.
>>>
>>> Unfortunately we didn't get very far in trying to solve the  
>>> problem I
>>> reported:
>>>
>>> http://lists.freedesktop.org/archives/cairo/2006-July/007344.html
>>>
>>> I did get far enough to see that it looks like Preview *is*  
>>> rendering
>>> the missing curves, just not at the desired offset:
>>>
>>> http://lists.freedesktop.org/archives/cairo/2006-July/007463.html
>>>
>>> Note that the glyph difficulties reported in the latter mail have
>>> already been resolved in the current version of cairo; only the  
>>> curve
>>> offset problem remains for me.
>>> http://cairographics.org/cgi-bin/mailman/listinfo/cairo
>>
>> This is a bug in cairo.  The generated PDF output from cairo:
>>
>> 10 M 100 100 m 100 200 l q 2 0 0 2 0 0 cm
>> S Q
>>
>> is undefined according to the PDF spec version 1.6.  According to  
>> Figure
>> 4.1 Graphics Objects on page 167, all gstate manipulations should  
>> occure
>> before path construction that should be followed by path-painting
>> operations.  It further clarifies on the following page:
>>
>> "Note: A content stream whose operations violate these rules for
>> describing graphics objects can produce unpredictable behavior, even
>> though it may display and print correctly."
>>
>> and:
>>
>> "A graphics object also implicitly includes all graphics state
>> parameters that affect its behavior. For instance, a path object  
>> depends
>> on the value of the current color parameter at the moment the path
>> object is defined. The effect is as if this parameter were  
>> specified as
>> part of the definition of the path object."
>>
>>
>> Simply moving the cm operator before path construction should fix it:
>>
>> 10 M q 2 0 0 2 0 0 cm 100 100 m 100 200 l
>> S Q
>>
>>
>> Any takers?
>
> Should be fixed now, in this commit:
>
>   e1ded5b1e042c8cefa7f136228d5a63a7bdf84b5
>
> -- 
> behdad
> http://behdad.org/
>
> "Commandment Three says Do Not Kill, Amendment Two says Blood Will  
> Spill"
>         -- Dan Bern, "New American Language"
>

--
Ken Treis
Miriam Technologies, Inc.