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Render math in RSS with MathML #584

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Render math in RSS with MathML #584

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cfd1b0a
Render math in RSS with MathML
armanbilge Feb 19, 2026
f10d675
Link to katex options doc
armanbilge Feb 19, 2026
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34 changes: 25 additions & 9 deletions build.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -283,9 +283,9 @@ object LaikaCustomizations {
SpanDirectives.create("math") {
import SpanDirectives.dsl.*
rawBody.map { body =>
RawContent(
NonEmptySet.of("html", "rss"),
KaTeX(body, false)
SpanSequence(
RawContent(NonEmptySet.of("html"), KaTeX(body, false)),
RawContent(NonEmptySet.of("rss"), KaTeX(body, false, "mathml"))
Comment on lines +287 to +288
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@valencik valencik Feb 19, 2026

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So the idea is roughly:

We register a @math directive, usable as a span or block.
It is formatted as a span with to pieces of content (SpanSequence).
This first RawContent only renders if we are targeting the html format, and in that case we use the default of KaTex output which is htmlAndMathml.
The second RawContent only renders if we are targeting our custom rss format in which case we use the mathml output.

)
}
}
Expand All @@ -294,10 +294,13 @@ object LaikaCustomizations {
BlockDirectives.create("math") {
import BlockDirectives.dsl.*
rawBody.map { body =>
RawContent(
NonEmptySet.of("html", "rss"),
KaTeX(body, true),
Styles("bulma-has-text-centered")
BlockSequence(
RawContent(
NonEmptySet.of("html"),
KaTeX(body, true),
Styles("bulma-has-text-centered")
),
RawContent(NonEmptySet.of("rss"), KaTeX(body, true, "mathml"))
)
}
},
Expand Down Expand Up @@ -342,6 +345,13 @@ object LaikaCustomizations {
val defaultRenderer = {
case (fmt, Title(_, _)) =>
"" // don't render title b/c it is in the RSS metadata
case (fmt, RawContent(formats, content, options)) =>
if (formats.contains("rss")) // only render content designated for RSS
HTML.defaultRenderer(
fmt,
RawContent(NonEmptySet.of("html"), content, options)
)
else ""
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@valencik valencik Feb 19, 2026

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And here, in the custom RSS render format, we are saying we should only render RawContent if it's format specifically has rss in it, otherwise return the empty string (as opposed to using the default html renderer, which is what we had been doing).

So would this mean that raw html content, like the every.org button on https://typelevel.org/foundation/ would not render in RSS at all anymore?

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@armanbilge armanbilge Feb 19, 2026

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So would this mean that raw html content, like the every.org button on typelevel.org/foundation would not render in RSS at all anymore?

It doesn't, because perhaps counter-intuitively I implemented the @:html directive to output content for both HTML and RSS!

typelevel.github.com/build.scala

Lines 330 to 335 in cfd1b0a

BlockDirectives.create("html") {
import BlockDirectives.dsl.*
rawBody.map { body =>
RawContent(NonEmptySet.of("html", "rss"), body)
}
}

case (fmt, elem) => HTML.defaultRenderer(fmt, elem)
}

Expand Down Expand Up @@ -436,12 +446,18 @@ object KaTeX {
ctx.getBindings("js").getMember("katex")
}

def apply(latex: String, displayMode: Boolean = false): String =
def apply(
latex: String,
displayMode: Boolean = false,
output: String = "htmlAndMathml"
): String =
synchronized {
// https://katex.org/docs/options
val options = Map(
"throwOnError" -> true,
"strict" -> true,
"displayMode" -> displayMode
"displayMode" -> displayMode,
"output" -> output
)
katex.invokeMember("renderToString", latex, options.asJava).asString
}
Expand Down