feat: add alt parameter to math.equation

crates/typst-library/src/math/equation.rs

@@ -1,6 +1,7 @@
 use std::num::NonZeroUsize;
 
 use codex::styling::MathVariant;
+use ecow::EcoString;
 use typst_utils::NonZeroExt;
 use unicode_math_class::MathClass;
 
@@ -47,6 +48,9 @@ use crate::text::{FontFamily, FontList, FontWeight, LocalName, TextElem};
 /// [main math page]($category/math).
 #[elem(Locatable, Synthesize, ShowSet, Count, LocalName, Refable, Outlinable)]
 pub struct EquationElem {
+    /// An alternative description of the mathematical equation.
+    pub alt: Option<EcoString>,
+
     /// Whether the equation is displayed as a separate block.
     #[default(false)]
     pub block: bool,

crates/typst-library/src/model/link.rs

@@ -88,7 +88,7 @@ use crate::text::{LocalName, TextElem};
 ///   generated.
 #[elem(Locatable)]
 pub struct LinkElem {
-    /// A text describing the link.
+    /// An alternative description of the link.
     pub alt: Option<EcoString>,
 
     /// The destination the link points to.

crates/typst-library/src/visualize/image/mod.rs

@@ -124,7 +124,7 @@ pub struct ImageElem {
     /// The height of the image.
     pub height: Sizing,
 
-    /// A text describing the image.
+    /// An alternative description of the image.
     pub alt: Option<EcoString>,
 
     /// How the image should adjust itself to a given area (the area is defined

crates/typst-pdf/src/tags/mod.rs

@@ -123,9 +123,9 @@ pub(crate) fn handle_start(
         } else {
             TagKind::Figure.with_alt_text(alt)
         }
-    } else if let Some(_) = elem.to_packed::<EquationElem>() {
-        // TODO: alt text
-        TagKind::Formula.into()
+    } else if let Some(equation) = elem.to_packed::<EquationElem>() {
+        let alt = equation.alt.get_as_ref().map(|s| s.to_string());
+        TagKind::Formula.with_alt_text(alt)
     } else if let Some(table) = elem.to_packed::<TableElem>() {
         let table_id = gc.tags.next_table_id();
         let summary = table.summary.get_as_ref().map(|s| s.to_string());