On Tuesday, 28 September, 2021 at 10:36:04 pm UTC+5:30 John MacFarlane wrote:

Looking at the HTML using the browser's Inspect feature, I
see that reveal.js is adding a div devoted to backgrounds,
which uses a background-image-hash attribute. This may be
constructed improperly for data URIs; anyway, this is one
thing to investigate here.

John MacFarlane <j...@berkeley.edu> writes:

> Not sure what is happening here, but yes, an issue on the tracker
> would be welcome.
>
> I note also that because the data-background-image attribute
> is retained on the h1 element as well as being propagated to
> the section element, we get two copies of the encoded image.
> That is bad. See also https://github.com/jgm/pandoc/issues/5965
>
>
> christophe dervieux <christoph...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:
>
>> Hello,
>>
>> Here is a reproducible example of the issue
>>
>> curl --output background.jpg -L 'https://unsplash.com/photos/8OyKWQgBsKQ/download?force=true&w=1920'
>>
>> echo "# Slide {data-background-image='background.jpg'}" > slide.md
>> echo "" >> slide.md
>> echo "Content" >> slide.md
>>
>> # Not self contained
>> pandoc -t revealjs -s -o slide.html --metadata title="test" slide.md
>>
>> # Self contained
>> pandoc -t revealjs --self-contained -o slide-self-contained.html --metadata title="test" slide.md
>>
>> When using self-contained, the background image is no more working. Pandoc
>> encodes to data: but it seems reveal.js does not know how to handle it. It
>> split the encoded data: in two url component.
>>
>> It seems like a change in reveal 4 as using the same slide.md file with
>> different version seems to break.
>>
>> What I tried:
>>
>> - Pandoc 2.9.2.1 : last one compatible with reveal.js 3 I believe
>>
>> pandoc.exe -t revealjs --self-contained -o slide-self-contained.html --metadata title="test" -V revealjs-url=https://unpkg.com/reveal.js@3/ slide.md
>>
>> Works as expected
>> - Pandoc 2.10: First to use reveal.js 4
>>
>> pandoc.exe -t revealjs --self-contained -o slide-self-contained.html --metadata title="test" -V revealjs-url=https://unpkg.com/reveal.js@4/ slide.md
>>
>>
>> So it seems that something broke when upgrading.
>>
>> Is this a known issue ?
>> Should I open an issue in Pandoc to track ? I believe this could be
>> something in reveal.js not handling correctly encoded data: field.
>>
>> MANUAL still says (
>> https://pandoc.org/MANUAL.html#background-in-reveal.js-and-beamer)
>>
>> Background images can be added to self-contained reveal.js slideshows and
>> to beamer slideshows.
>>
>> But maybe self-contained and revealjs does not work well.
>>
>> Thank you
>>
>>
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