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