Support a few MathML tags.

crates/typst-html/src/encode.rs

@@ -80,9 +80,13 @@ fn write_element(w: &mut Writer, element: &HtmlElement) -> SourceResult<()> {
         w.buf.push('"');
     }
 
+    if tag::is_self_closing_foreign(element.tag) {
+        w.buf.push_str(" /");
+    }
+
     w.buf.push('>');
 
-    if tag::is_void(element.tag) {
+    if tag::is_void(element.tag) || tag::is_self_closing_foreign(element.tag) {
         return Ok(());
     }
 

crates/typst-library/src/html/dom.rs

@@ -472,6 +472,26 @@ pub mod tag {
         wbr
     }
 
+    pub mod math {
+        use super::HtmlTag;
+
+        tags! {
+            math
+            mfrac
+            mi
+            mmultiscripts
+            mprescripts
+            mrow
+            msub
+            msup
+            munderover
+        }
+
+        pub fn is_self_closing(tag: HtmlTag) -> bool {
+            matches!(tag, self::mprescripts)
+        }
+    }
+
     /// Whether nodes with the tag have the CSS property `display: block` by
     /// default.
     ///
@@ -569,8 +589,9 @@ pub mod tag {
         )
     }
 
-    /// Whether this is a void tag whose associated element may not have a
-    /// children.
+    /// Whether this is a void tag whose elements may not have children.
+    ///
+    /// Source: <https://html.spec.whatwg.org/#void-elements>
     pub fn is_void(tag: HtmlTag) -> bool {
         matches!(
             tag,
@@ -591,6 +612,18 @@ pub mod tag {
         )
     }
 
+    /// Whether this is a self-closing foreign tag.
+    ///
+    /// A foreign tag is a tag from the MathML or the SVG namespace
+    /// <https://html.spec.whatwg.org/#foreign-elements>.
+    ///
+    /// We use this to determine whether a tag needs to be
+    /// terminated with `/ >` (foreign elements) instead of just `>`.
+    /// See <https://html.spec.whatwg.org/#start-tags>.
+    pub fn is_self_closing_foreign(tag: HtmlTag) -> bool {
+        math::is_self_closing(tag)
+    }
+
     /// Whether this is a tag containing raw text.
     pub fn is_raw(tag: HtmlTag) -> bool {
         matches!(tag, self::script | self::style)

crates/typst-utils/src/pico.rs

@@ -219,6 +219,7 @@ mod exceptions {
         "h5",
         "h6",
         "historical-ligatures",
+        "mmultiscripts",
         "number-clearance",
         "number-margin",
         "numbering-scope",