Figure caption not showing when using inline SVG

[netw0rkf10w]

Hello,

I'm using this filter for converting TikZ code to SVG in Quarto. When using the filter as is, it works (an example can be found at https://raw.githubusercontent.com/pandoc-ext/diagram/main/test/input-tikz.md). However, when I changed the code to replace the SVG file with inline SVG, the caption is not showing (I checked the output HTML and the figure container was not even generated).

More precisely, in the original code, an SVG image is created and store in img, then:

-- Use the block's filename attribute or create a new name by hashing the image content.
  local basename, _extension = pandoc.path.split_extension(
    props.filename or pandoc.sha1(img)
  )
  local fname = basename .. '.' .. extension_for_mimetype[imgtype]
  -- Store the data in the media bag:
  pandoc.mediabag.insert(fname, imgtype, img)
  -- Create a figure that contains just this image.
  local img_obj = pandoc.Image(props.alt, fname, "", props['image-attr'])
  return pandoc.Figure(pandoc.Plain{img_obj}, props.caption, props['fig-attr'])

What I did is, instead of creating a file in the media bag, I used directly the SVG as an inline HTML element:

return pandoc.Figure(pandoc.RawInline('html', img), props.caption, props['fig-attr'])

(the above line replaces the entire previous code block)

Using Pandoc alone, it worked:

quarto pandoc --lua-filter filters/diagram.lua -s tikz.qmd  -o tikz.html

However, when rendering tikz.qmd containing

filters:
  - diagram.lua

with Quarto, the SVG is displayed but not in a figure container and thus there's no caption.

Could you please help? Thank you very much in advance!

[mcanouil]

Could you share a more actionable example, such as a complete and small Quarto document using your filter?

[mcanouil]

@netw0rkf10w I wrote the repository in one of my answer¹, see https://github.com/pandoc-ext/diagram.

Footnotes

1. https://github.com/quarto-dev/quarto-cli/discussions/5266#discussioncomment-5692544 ↩

[netw0rkf10w]

@mcanouil Sorry I thought @tarleb was referring to a repo of Quarto. Obviously I knew about the pandoc-ext repo because that's where I took the filter from. And I'm afraid that it is not appropriate to raise an issue there, because this issue is specific to Quarto and not Pandoc in general. As I mentioned in my first post, the filter works just fine with Pandoc: when doing quarto pandoc --lua-filter filters/diagram.lua -s tikz.qmd -o tikz.html, it works! Thus, neither Pandoc nor the filter itself is the problem I guess.

[mcanouil]

It seems so as I said, it's likely an issue on how figure environment are handled within Quarto which might not be completely compatible with the filter at this moment and likely to be something for 1.4.

[tarleb]

Workaround: use the original diagram.lua filter and run the below filter after the Quarto filters:

function Image (img)
  if img.src:match '%.svg$' then
    local mime_type, contents = pandoc.mediabag.lookup(img.src)
    if mime_type == 'image/svg+xml' and contents then
      return pandoc.RawInline('html', contents:gsub('^.*(%<svg%f[%s])', '%1'))
    end
  end
end

The time at which quarto filters are run can be controlled by using the special quarto filter:

filters:
  - diagram.lua
  - quarto
  - inline-svg.lua

(Untested, so might need some tweeking.)

[mcanouil]

I just tried it and it worked.

[mcanouil]

I opened #5297 to track this further in the future.

[netw0rkf10w]

@tarleb It works like a charm, thanks a lot! I've just realised that you are actually the author of diagram.lua (not sure why I didn't notice this before). Thanks for the filter!
Thanks to @mcanouil as well for the discussion!