[xep-support] uri(file:xxx) links

[Victor Mote]

Nikolai Grigoriev wrote: 

> Victor,
> 
> > <fo:basic-link external-destination="url(file:aruser.pdf)">
> > <fo:inline color="blue">Accounts Receivable</fo:inline> 
> > </fo:basic-link> ...
> > However, when I follow the link noted above, the document 
> opens as if 
> > "fit" or "fit-height" were the setting.
> 
> You are right: for PDF links, we create a remote go-to action 
> in PDF that addresses the first page, and specifies scale 
> factor as /Fit. 
> The reason is, in a remote go-to action we need to explicitly 
> specify destination in the target file. And the destination 
> specifier should either provide an explicit endpoint 
> coordinate, or set the scale factor so that it fits the 
> viewport by the respective dimension. 
> 
> To work around this limitation, I suggest adding a fragment 
> identifier to the URL:
> 
> <fo:basic-link external-destination="url(file:aruser.pdf#docstart)">
> 
> where 'docstart' is an id of some element at the beginning of 
> the tagret document. Your aruser.fo could begin like this:
> 
> <fo:page-sequence ...
>   <fo:flow ...
>     <fo:block id="docstart"/>

That makes sense. I'll work on something along these lines.

> This makes Acrobat jump to the respective location using the 
> scale factor specified by the named destination 'docstart' 
> _inside aruser.pdf_; typically, it simply inherits scale 
> factor from the context. 
> 
> If you provide a non-existing fragment ID, Acrobat will jump 
> to the first page of the document (and don't even generate 
> errors). However, I am not sure this is a clean solution; I 
> believe adding a real @id to the beginning of the document is 
> a cleaner approach.

I had already noticed that providing an empty fragment identifier caused the
desired behavior, and agree that it is not a very clean approach. After
digging around on this
issue a bit, I see that, at least based on the behavior of Acrobat 6, I may
have misunderstood the meaning of some of the document settings in a PDF
file. The "Open To" page number seems only to be used when the document is
explicitly & directly opened, not when it is opened (without a fragment
identifier) by following a link from another document. I wouldn't be
surprised to find out that this is a bug in Acrobat 6, but in any case, it
does look like the safest thing to do is add an explicit fragment
identifier.

> > The desired behavior is for aruser.pdf to open with the "fit-width" 
> > initial zoom. 
> 
> Thank you for providing the use case. Right now, it is not 
> evident for me how it can be done without parsing the target 
> PDF file; we are going to look into it in more details.
> 
> > When I try to use the Acrobat "link" tool to see the 
> properties of the 
> > link, I get the following message: "There was a problem 
> reading this 
> > document (18)."
> 
> I would be grateful if you could send me your PDF file 
> off-list to support at renderx.com to examine. In general, I 
> have an impression that remote go-to actions are poorly 
> supported in Acrobat: it executes them well but creates a 
> terrible mess trying to edit them (at least Acrobat 5; did't 
> try with 6).

I have sent (off-list) both the PDF file in question and the same document
created with another application for reference. I definitely don't think you
should have to parse the target PDF file for this use-case. After you
resolve the issue causing the errors in the links, I think (based on the
behavior of the reference file) that the behavior will be "correct",
althought that may be by accident.

Thanks again.

Victor Mote

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