Supports highlightjs using RevealHighlight or usual R Markdown way ?

[cderv]

R Markdown has current usually support for highlight.js through highlight: paramater: https://pkgs.rstudio.com/rmarkdown/reference/html_document.html

revealjs currently only support Pandoc's syntax highlighting through the rmarkdown::pandoc_highlight_args() function.

However, the template already have the loading of the library but it is not really included and I don't think that works

revealjs/inst/rmarkdown/templates/revealjs_presentation/resources/default.html

Lines 21 to 26 in 1b20483

	$if(highlightjs)$
	<link rel="stylesheet"
	href="$highlightjs$/$if(highlightjs-theme)$$highlightjs-theme$$else$default$endif$.css"
	$if(html5)$$else$type="text/css" $endif$/>
	<script src="$highlightjs$/highlight.js"></script>
	$endif$

Also, reveal.js seems to have support through a Plugin : https://revealjs.com/code/
This brings features like

• Line number : https://revealjs.com/code/#line-numbers-%26-highlights (which Pandoc also has)
• Step by Step highlight: https://revealjs.com/code/#step-by-step-highlights
• HTML Character escaping: https://revealjs.com/code/#html-entities-4.1.0

[cderv]

I think the above is really old code that was once used in rmarkdown but removed in rmarkdown 1.2
rstudio/rmarkdown@d4aaf99
following the switch to use highlightjs with htmldependency

We should use the revealjs way IMO

[cderv]

Currently, highlightjs is never used because of

revealjs/R/revealjs_presentation.R

Lines 228 to 229 in cc46ea0

	# highlight
	args <- c(args, pandoc_highlight_args(highlight, default = "pygments"))

which will only set Pandoc's highlighting.

In rmarkdown, highlightjs can be triggered using rmarkdown:::pandoc_html_highlight_args() and the default template.

So I believe no risk to remove this from the template.