[NTG-context] XML: Correct usage of hash symbol in url

[NTG-context] XML: Correct usage of hash symbol in url

[denis.maier]

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Hi,

I need to process URLs in XML documents differently depending on the target. Thanks to Hans and Thomas I can now deal with the attributes.
Now I need to prefix certain kind of targets with a certain URL (a web viewer for IIIF images in this particular case). The prefix contains a #, which, as a special character seems to cause an error. Adding a double hash seems to work, but those ## will end up in the link URL. How can I properly escape a single #? I've already tried using \Ux{23}, but that won't work either.

Best,
Denis

\setupinteraction[state=start]

\startxmlsetups xml:test
                \xmlsetsetup{#1}{*}{-}
                \xmlsetsetup{#1}{doc|element}{xml:*}
\stopxmlsetups

\xmlregisterdocumentsetup{test}{xml:test}

\startxmlsetups xml:doc
\xmlflush{#1}
\stopxmlsetups

\startluacode
     function xml.finalizers.tex.url(e,a)
         local u = #e > 0 and e[1].at[a]
         local s = u and lpeg.match(lpeg.patterns.urlunescaper,u)
         context(s)
     end
\stopluacode

\startxmlsetups xml:element
\xmldoifelse{#1}{.[@href and contains(@href,'https://iiif.ub.unibe.ch')]}

                {\goto{\xmlflush{#1}}[url(https://uv-v4.netlify.app/##?manifest=\xmlatt{#1}{href})]} % gives me two hashes in the Link

                %{\goto{\xmlflush{#1}}[url(https://uv-v4.netlify.app/#?manifest=\xmlatt{#1}{xlink:href})]} \par % does not work

                {\goto{\xmlflush{#1}}[url(\xmlatt{#1}{href})]}
\stopxmlsetups


\startbuffer[test]
<?xml version="1.0" encoding="UTF-8"?>
<doc>
<element href="https://iiif.ub.unibe.ch/presentation/v2.1/berner-inkunabeln/manifest/Inc%20I%20104%20fol%20a1r">IIIF-Link</element>
<element href="https://wiki.contextgarden.net/">Other Link</element>
</doc>
\stopbuffer

\starttext

\xmlprocessbuffer{test}{test}{}

\stoptext

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[NTG-context] Re: XML: Correct usage of hash symbol in url

[Hans Hagen via ntg-context]

On 8/25/2023 10:16 AM, denis.maier@unibe.ch wrote:
> Hi,
> 
> I need to process URLs in XML documents differently depending on the target. Thanks to Hans and Thomas I can now deal with the attributes.
> Now I need to prefix certain kind of targets with a certain URL (a web viewer for IIIF images in this particular case). The prefix contains a #, which, as a special character seems to cause an error. Adding a double hash seems to work, but those ## will end up in the link URL. How can I properly escape a single #? I've already tried using \Ux{23}, but that won't work either.
\#

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------

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[NTG-context] Re: XML: Correct usage of hash symbol in url / new upload

[Hans Hagen via ntg-context]

Hi Denis,

> I need to process URLs in XML documents differently depending on the target. Thanks to Hans and Thomas I can now deal with the attributes.
> Now I need to prefix certain kind of targets with a certain URL (a web viewer for IIIF images in this particular case). The prefix contains a #, which, as a special character seems to cause an error. Adding a double hash seems to work, but those ## will end up in the link URL. How can I properly escape a single #? I've already tried using \Ux{23}, but that won't work either.
The duplication of hashes is kind of special. Consider this:

\def\foo#1{#1 test ##}

\def\foo#1{#1 test\def\more##1{(##1)}}

the internal representation of #1 is a reference to parameter 1 while 
the ## becomes one # (cc parameter) in the second exmaple followed by a 
character 1 (cc other)

then, when tex serializes e.g. in tracing it duplicates the hash (with 
cc parameter) so that the user is not confused (an alternative could 
have been to indicate a parameter reference differently but changing 
that now is no real option - what symbol to use anyway?)

with lua(meta)tex opening up matters this duplication becomes a bit 
annoying so i decided to see if it could be avoided in some cases

first i decided to provide an escape, possible because we already have 
such mechanism using # (not advertised because it is still experimental)

then i decided to just not duplicate unless we trace

in the lowlevel macro manual there is a section added that goes in more 
detail

to come back to the escaping: here is a list:

#I  loop iteraor
#P  parent loop iterator
#G  grandparent loop iterator

#H  hash
#S  space (ascii 32)
#T  tab \t
#L  newline \n
#R  return \r
#X  backslash

considering

#N nbsp

and some more. Keep in mind that #1-#9 #A-#E are in use as parameter 
references

but in the case of your url's escaping should not be needed (hopefully)

Hans

ps. all kind of expereimental because it's a bit hairy and we don't want 
to loose compatibility (hashes get interpreted in the macro preamble, 
macro body, running text, serialization etc)

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------

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maillist : ntg-context@ntg.nl / https://www.ntg.nl/mailman/listinfo/ntg-context
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