Adding a second class onto the callouts works in html format but not revealjs format

[cderv]

Adding a second class onto the callouts for HTML works — One usage example is to target a callout using CSS

::: {.callout-note .my-callout}
Hello!
:::

And the CSS file:

.callout.callout-style-default.my-callout .callout-body {
    font-size: 1.0rem;
}

From a post by @jimjam-slam in #4755 (comment)

This works for HTML format as we pass attributes and classes, but not in revealjs format where it seems we don't.

[cderv]

@cscheid I think we need to adapt our callout custom node creation to allow passing attributes for revealjs format as we allow for html format. I can handle it for 1.4 or later, part of revealjs work.

[cscheid]

Agreed. I'm surprised that this doesn't work. I wonder if it's hiding a bigger bug.

[cderv]

I don't think so. From what I saw this morning, we are using a specific function for revealjs output

quarto-cli/src/resources/filters/quarto-pre/callout.lua

Lines 66 to 67 in 710f5b4

	elseif _quarto.format.isEpubOutput() or _quarto.format.isRevealJsOutput() then
	return epubCallout(node)

but we are not inheriting the node.attr when creating the callout, as we do for HTML with bootstrap

quarto-cli/src/resources/filters/quarto-pre/callout.lua

Lines 795 to 808 in 710f5b4

	local attributes = pandoc.List({"callout"})
	if type ~= nil then
	attributes:insert("callout-" .. type)
	end
	if hasIcon == false then
	attributes:insert("no-icon")
	end
	if title ~= nil then
	attributes:insert("callout-titled")
	end
	attributes:insert("callout-style-" .. calloutAppearance)
	return pandoc.Div({calloutBody}, pandoc.Attr(node.id or "", attributes))

I think we should have a specific revealjsCallout(), or non boostrap HTML callout. I don't know if we can pass any class and attributes to epub structure. Anyway, I was planning to make a proposal for 1.4 later. Happy to let you handle it as you know better this part of the code.