Re: epub : footnote backlink character not rendered by Kobo fonts

[John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org>]

A custom writer is probably overkill. It would be easier to write
a small script that unzips the epub, does search and replace
on the xhtml files, and then zips it back up again.  This could
be 3 lines of shell script.

That said, this is a long standing issue and we might consider
using a different character or making it configurable:

https://github.com/jgm/pandoc/issues/3149


William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org> writes:

> This probably won't be the answer that you wanted, but you could use a
> custom writer, e.g., based on the provided sample.lua. See
> https://pandoc.org/MANUAL.html#custom-writers.
>
> Here's the relevant code (this isn't all the code relating to footnotes,
> but it's the bit that has the special character!):
>
> function Note(s)
>     local num = #notes + 1
>     -- insert the back reference right before the final closing tag.
>     s = string.gsub(
>         s, '(.*)</', '%1 <a href="#fnref' .. num ..  '">&#8617;</a></')
>     -- add a list item with the note to the note table.
>     table.insert(notes, '<li id="fn' .. num .. '">' .. s .. '</li>')
>     -- return the footnote reference, linked to the note.
>     return '<a id="fnref' .. num .. '" href="#fn' .. num ..
>         '"><sup>' .. num .. '</sup></a>'
> end
>
> On Tue, 21 Sept 2021 at 13:23, Vin Cent <irakay17-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>> Ok, after some more reading, I'm still unsure how to proceed ; and I
>> actually don't see how I could to that with a filter.
>> I have dumped pandoc's native output format ; and the character I need to
>> replace is not part of it. I guess it is added at the time of pandoc's
>> writing the output document.
>> I don't know how how I can replace that character. Hopefully there is a
>> pandoc setting I can tune so that I won't need to replace it at some late
>> stage.
>>
>>
>>
>> On Tuesday, September 21, 2021 at 10:42:14 AM UTC+2 Vin Cent wrote:
>>
>>> Sorry for answering myself. I have RTFMed a bit in the while.
>>> I actually hint this can be simply done with a LUA filter.
>>> I will try to implement it as a self-exercice and report the result here.
>>>
>>> On Tuesday, September 21, 2021 at 9:34:26 AM UTC+2 Vin Cent wrote:
>>>
>>>> Hi,
>>>>
>>>> I am generating epub3 from latex source.
>>>> I was wondering why footnotes show a backlink to the original text when
>>>> I display the document in calibre, and why they do not when I display the
>>>> document on a kobo reader...
>>>>
>>>> ... until I found the backlink is indeed well present. It is "just" not
>>>> displayed by kobo because the character set (by pandoc, I think) has no
>>>> rendering on their font.
>>>>
>>>> The backlink character, copied and pasted from the .epub document
>>>> itself, seems to be "↩︎".
>>>>
>>>> I see two possible tricks here so that the link will appear on kobo :
>>>> 1. Change the character to another one that would be rendered by kobo.
>>>> 2. Change the default font of the document to one that has rendering for
>>>> that character.
>>>>
>>>> I have tried all available fonts on my device. There are actually three
>>>> classes of them.
>>>> (Listing them all below, this might be of interest to somebody in the
>>>> future)
>>>>
>>>> Avenir Next ; Georgia ; Kobo Nickel : these fonts render absolutely
>>>> nothing for that character, leading the human to believe the backlink does
>>>> not exist. It is present, clickable, just not rendered.
>>>>
>>>> Amasis ; Caecilia ; Gill Sans ; Malabar ; OpenDislexic : these fonts
>>>> render "__" for that character. I find it "better" than the first family,
>>>> but still not great. It is not obvious for a non-tehnical human that this
>>>> is a backlink to the text.
>>>>
>>>> AR UDJingxihei ; Kobo UD Kakugo ; Kobo Tsukishi Mincho : display
>>>> oriental character (I think this is chinese / japanese depending on font)
>>>> for the backlink character.
>>>>
>>>>
>>>> Therefore, I tend to favor the first solution. Do you guys know of a way
>>>> to customize the "backlink ↩︎" character set by pandoc in epub ?
>>>> Or is there a third approach ?
>>>>
>>>> Thanks,
>>>>
>>>> Vincent
>>>>
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