Figure captions not inheriting master slide font settings

[yonicd]

Explain the problem.

When pandoc renders a pptx from an md with a figure in it that has a caption, it does not use the font defined in the master slide template for the caption.

• In this example in the repo I set the master slide fonts to Verdana and the subtitle comes out in Calibri.
• This behavior is the same with tables and the tables captions
• This behavior was initially posted in a quarto discussion and was diagnosed as a bug in pandoc and not quarto by the developers.

git clone [email protected]:yonicd/test_pandoc_pptx.git
pandoc test.md -o test.pptx --reference-doc=template.pptx

Pandoc version

pandoc --version
pandoc.exe 3.2
Features: +server +lua
Scripting engine: Lua 5.4

[jgm]

Currently the caption is just added in a text box after the image. No special style is applied. I imagine Word does something else, perhaps attaching a style, but I'm not really familiar with pptx format so this would take a while to debug.

[yonisidi]

Do you mean here?

[jgm]

That's a relevant data structure but that's not where the XML is being written.

The thing to figure out first would be what pandoc should be including in the XML in order to have these styled correctly. (I understand how styles work in docx, but I know nothing about pptx.) If we figure that out, I think changing the code should be relatively straightforward.

[yonisidi]

So the original xml looks like this (after converting to zip and unarchiving the output pptx):

<p:txBody>
  <a:bodyPr/>
  <a:lstStyle/>
  <a:p>
    <a:pPr lvl="0" indent="0" marL="0" algn="ctr">
      <a:buNone/>
    </a:pPr>
    <a:r>
      <a:rPr/>
      <a:t>Image Caption</a:t>
    </a:r>
  </a:p>
</p:txBody>

Based on this SO answer it looks like it gives a roadmap on what is expected in openxml:

example solution

<p:txBody>
  <a:bodyPr/>
  <a:lstStyle/>
  <a:p>
    <a:pPr xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" lvl="0" indent="0" marL="0" algn="ctr">
      <a:buFont typeface="Arial" charset="0" pitchFamily="34" panose="020B0604020202020204"/>
    </a:pPr>
    <a:r>
      <a:rPr/>
      <a:t>Image Caption</a:t>
      <a:rPr lang="en-US" dirty="0" sz="900"/>
    </a:r>
  </a:p>
</p:txBody>

[jgm]

This is just specifying a particular typeface and size directly. I thought the idea was to make this sensitive to some kind of global style?

[yonicd]

Yes, you are correct. That is the intent.

[jgm]

That's the part I don't know how to do.