Odd choice, usually that's how you'd show the (possibly syntax-highlighted) code as-is, not execute/render it in situ.
E.g. what if I want a document that says 'this pikchr code generates this'? I'd expect to write something like:
```pikchr
arrow 200% "whatever"
```
renders:
$pikchr
arrow 200% "whatever"
$
If you want to see it both ways, Fossil renders the diagrams with an Alt or Ctrl-click handler attached (depending on platform) that toggles between the SVG and the fixed-width source code view.
And if you don't like the modifier key, you can tag a diagram "pikchr toggle" to make it toggle with a simple left-click.
You could reasonably put options on the fenced-code-block header line:
```pikchr --source
...
```
```pikchr --caption # caption rendered figure with source
...
```
But at that point, you might as well just use Fossil as a CMS. :)
It's a great little diagram language that's quite capable, and I think of it like a modern web upgrade to Brian Kernighan's PIC.
Here is my earliest Pikchr effort: https://lumosql.org/src/not-forking (click to see source.)
Pikchr diagrams are crisp and precise with zero configuration. Mermaid diagrams are difficult to make render as nicely as the screenshots show (https://mermaid-js.github.io ) and easier to confuse with ambiguous syntax.
With the addition of 5 lines Lua, Pandoc now handles Pikchr in Markdown documents: https://groups.google.com/g/pandoc-discuss/c/zZSspnHHsg0/m/m...