Re: linking to a locally installed epub file

[Gavin Smith]

On Fri, Aug 05, 2022 at 02:56:48PM +0200, Patrice Dumas wrote:
> Hello,
> 
> Referring to another manual from within a manual (using @pxref and
> similar), converted to the EPUB format, can be done as usual for HTML
> following the HTML XREF specification, if there is an entry in an
> htmlxref.cnf file.  When there is no entry in an htmlxref.cnf, however,
> the generated link is bogus (and makes the EPUB invalid).

Could the href attribute be omitted from the <a> tag in that case?

> 
> Even if there is an entry in htmlxref.cnf, it would also be nice to be
> able to open a local epub file instead of going to the web HTML manual
> (for now this would be at manual conversion time, if it could be
> implemented).

This is what the data-manual attribute was for.  I do not know all
the whys and wherefores of whether custom attributes are valid for
EPUB, but at

https://www.w3.org/publishing/epub3/epub-contentdocs.html#sec-xhtml-custom-attributes

> Reading Systems MAY introduce functionality not defined in this
> specification to enhance the rendering of EPUB Publications. To
> facilitate this experimentation, vendors MAY define custom attributes
> for use in XHTML Content Documents.
> 
> Custom attributes MAY be included on any element in an XHTML Content
> Document provided such attributes are from a foreign namespace,
> which is defined as...

- it implies that there might be some way of using custom attributes.  I
think the name space appears as a string before the attribute name,
separated by a colon.  So in "epub:type", "epub" is the namespace.
Perhaps we could use "texinfo:manual", and declare the "texinfo"
namespace following https://www.w3.org/TR/xml-names/ (I haven't
read that link, though).  We might also need "texinfo:node" to give the
node name of the target.

By no means do I think this is a priority at present.  This could
cause problems for EPUB readers and may not be a natural use of
the format.

> I have not found anywhere information on how to link to an EPUB file
> for these two use cases.  Do you know how to setup a link to an EPUB
> file, and even to some content (an xhtml file in an EPUB container
> and a #something target in the xhtml file)?  Maybe using an URL, but
> other ways would be ok too.

I doubt there is a recognized kind of URL for linking within EPUB
files.

> Ultimately, that could allow to mimick what can be done in Info, or,
> hopefully, in the future, in HTML for local browsing.
> 
> -- 
> Pat
>