Change mermaid output from svg (bug) to pdf

[lsignac]

Continuation of https://github.com/pandoc/lua-filters/pull/266 svg output does not work for graphs so the mermaid filter has been changed to produce pdf output instead.

[tarleb]

Thanks. It's surprising that this would be necessary, I'll take a closer look.

The old code should be removed instead of commented out. We'll also have either install Inkscape for the Mermaid CI tests, or switch to LaTeX as the output format for those tests.

[lsignac]

Sorry for old code. I just forgot to remove it.

For the svg problem... I thought it was related to https://github.com/mermaid-js/mermaid-cli/issues/112. But I am not sure anymore...

I tested with this file :

test.md

Document is compiled to pdf with :

pandoc --lua-filter diagram_without_my_PR.lua test.md -t latex -o test.pdf

In the PDF result values 1 and 2 do not appear in the nodes.

But with :

pandoc --lua-filter diagram_with_my_PR.lua test.md -t latex -o test.pdf

Then, values 1 and 2 appear.

BUT... ( :) )

If I manually compile the mermaid graph to svg (mmdc --input graph.mmd --output graph.svg)

graph TD
      A["1"]
      B["2"]
      A --> B

The resulting graph.svg seems OK in firefox (1 and 2 printed inside nodes).

Then I do :

---
title: Sample file 2
---

![](graph.svg)

and compile this file with pandoc... and numbers have disappeared. So may be the problem is related to the way pandoc processes svg...

[tarleb]

I checked and indeed, this seems to be a PDF-to-SVG conversion issue. I'll modify the code and pass an indicator to the generator that indicates whether is should prefer PDF over SVG. That should fix it.

[tarleb]

I didn't like the PDF output produced by mermaid, so the filter opts for PNG output when PDF/LaTeX is the targeted output format.

[lsignac]

You didn't like ? It seemed to me that images were exactly the same, except that you can not zoom PNG indefinitely and you wll have to finely tune resolution to get a high quality printed document without generating 100Meg pngs. Just to be sure, can you explain what's wrong with PDF output ?

[tarleb]

pdf-mermaid.pdf png-mermaid.pdf

[tarleb]

I see now that you included the -f flag in the PR. That should fix it.

[lsignac]

Oh yes. Please, add the -f flag and keep pdf output that is better quality than png. I hope the issue with svg (mermaid or pandoc...) will be addressed soon and that it will be safe for your filter to fall back to svg everywhere. Thank you.

[tarleb]

Already done :slightly_smiling_face: