Loss of vertical navigation with reveal.js

Loss of vertical navigation with reveal.js

[R (Chandra) Chandrasekhar]

I am experiencing perplexing behaviour when generating reveal.js slides.

I have in my YAML header the following fragment:

---
theme: black
transition: none
slide-level: 2
---

Until yesterday, I was able to get horizontal title slides with a 
level-1 header and vertically stacked content slides with a level-2 header.

But today. I cannot seem to get that behaviour. The horizontal ("title") 
slide and the first vertical ("content") slide appear on the same slide 
and navigation keys are not available to dig down vertically. Other 
vertical slides do not appear at all.

I have been using pandoc 1.19.2.1 from the package for Manjaro Linux.

Yesterday, I started using pandoc 2.0.1 from the site binary tarball 
because I wanted to use the reveal.js mathjax plugin.

I am using a bash script to compile. For pandoc 2.0 it is:

pandoc --from markdown+smart --to revealjs --standalone --self-contained 
--css "$custom" --mathjax --output "$dest" "$source"

and for pandoc 1.19.2 it is:

pandoc --from markdown --to revealjs --standalone --smart 
--self-contained --css "$custom" --output "$dest" "$source"

I can switch between the two versions of pandoc in my bash script.

I had a Manjaro software update yesterday and that might have introduced 
some (regression?) bugs. I really do not know.

Any pointers as to why this is happening would be appreciated.

Also, is there an online site where I can try out a test file to see if 
I get the horizontal and vertical reveal.js output I expect and that I 
previously had.

Thanks.

Chandra