feat: generate tags for bibliographies

crates/typst-layout/src/rules.rs

@@ -23,7 +23,7 @@ use typst_library::model::{
     LinkElem, ListElem, Outlinable, OutlineElem, OutlineEntry, ParElem, ParbreakElem,
     QuoteElem, RefElem, StrongElem, TableCell, TableElem, TermsElem, Works,
 };
-use typst_library::pdf::{ArtifactElem, EmbedElem, PdfMarkerTag, PdfMarkerTagKind};
+use typst_library::pdf::{ArtifactElem, EmbedElem, PdfMarkerTag};
 use typst_library::text::{
     DecoLine, Decoration, HighlightElem, ItalicToggle, LinebreakElem, LocalName,
     OverlineElem, RawElem, RawLine, ScriptKind, ShiftSettings, Smallcaps, SmallcapsElem,
@@ -452,10 +452,7 @@ const OUTLINE_RULE: ShowFn<OutlineElem> = |elem, engine, styles| {
     }
 
     // Wrap the entries into a marker for pdf tagging.
-    seq.push(
-        PdfMarkerTag::new(PdfMarkerTagKind::OutlineBody, Content::sequence(entries))
-            .pack(),
-    );
+    seq.push(PdfMarkerTag::OutlineBody(Content::sequence(entries)));
 
     Ok(Content::sequence(seq))
 };
@@ -543,25 +540,29 @@ const BIBLIOGRAPHY_RULE: ShowFn<BibliographyElem> = |elem, engine, styles| {
 
         let mut cells = vec![];
         for (prefix, reference) in references {
+            let prefix = PdfMarkerTag::ListItemLabel(prefix.clone().unwrap_or_default());
             cells.push(GridChild::Item(GridItem::Cell(
-                Packed::new(GridCell::new(prefix.clone().unwrap_or_default()))
-                    .spanned(span),
+                Packed::new(GridCell::new(prefix)).spanned(span),
             )));
+
+            let reference = PdfMarkerTag::BibEntry(reference.clone());
             cells.push(GridChild::Item(GridItem::Cell(
-                Packed::new(GridCell::new(reference.clone())).spanned(span),
+                Packed::new(GridCell::new(reference)).spanned(span),
             )));
         }
-        seq.push(
-            GridElem::new(cells)
-                .with_columns(TrackSizings(smallvec![Sizing::Auto; 2]))
-                .with_column_gutter(TrackSizings(smallvec![COLUMN_GUTTER.into()]))
-                .with_row_gutter(TrackSizings(smallvec![row_gutter.into()]))
-                .pack()
-                .spanned(span),
-        );
+
+        let grid = GridElem::new(cells)
+            .with_columns(TrackSizings(smallvec![Sizing::Auto; 2]))
+            .with_column_gutter(TrackSizings(smallvec![COLUMN_GUTTER.into()]))
+            .with_row_gutter(TrackSizings(smallvec![row_gutter.into()]))
+            .pack()
+            .spanned(span);
+        // TODO(accessibility): infer list numbering from style?
+        seq.push(PdfMarkerTag::Bibliography(true, grid));
     } else {
+        let mut body = vec![];
         for (_, reference) in references {
-            let realized = reference.clone();
+            let realized = PdfMarkerTag::BibEntry(reference.clone());
             let block = if works.hanging_indent {
                 let body = HElem::new((-INDENT).into()).pack() + realized;
                 let inset = Sides::default()
@@ -573,8 +574,9 @@ const BIBLIOGRAPHY_RULE: ShowFn<BibliographyElem> = |elem, engine, styles| {
                 BlockElem::new().with_body(Some(BlockBody::Content(realized)))
             };
 
-            seq.push(block.pack().spanned(span));
+            body.push(block.pack().spanned(span));
         }
+        seq.push(PdfMarkerTag::Bibliography(false, Content::sequence(body)));
     }
 
     Ok(Content::sequence(seq))

crates/typst-library/src/pdf/accessibility.rs

@@ -3,7 +3,10 @@ use std::num::NonZeroU32;
 use typst_macros::{elem, func, Cast};
 use typst_utils::NonZeroExt;
 
-use crate::foundations::{Content, NativeElement, Smart};
+use crate::diag::bail;
+use crate::diag::SourceResult;
+use crate::engine::Engine;
+use crate::foundations::{Args, Construct, Content, NativeElement, Smart};
 use crate::introspection::Locatable;
 use crate::model::TableCell;
 
@@ -99,21 +102,28 @@ impl TableHeaderScope {
 }
 
 // Used to delimit content for tagged PDF.
-#[elem(Locatable)]
+#[elem(Locatable, Construct)]
 pub struct PdfMarkerTag {
+    #[internal]
     #[required]
     pub kind: PdfMarkerTagKind,
     #[required]
     pub body: Content,
 }
 
+impl Construct for PdfMarkerTag {
+    fn construct(_: &mut Engine, args: &mut Args) -> SourceResult<Content> {
+        bail!(args.span, "cannot be constructed manually");
+    }
+}
+
 macro_rules! pdf_marker_tag {
-    ($(#[doc = $doc:expr] $variant:ident,)+) => {
-        #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Cast)]
+    ($(#[doc = $doc:expr] $variant:ident$(($($name:ident: $ty:ident)+))?,)+) => {
+        #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
         pub enum PdfMarkerTagKind {
             $(
                 #[doc = $doc]
-                $variant
+                $variant $(($($ty),+))?
             ),+
         }
 
@@ -121,9 +131,12 @@ macro_rules! pdf_marker_tag {
             $(
                 #[doc = $doc]
                 #[allow(non_snake_case)]
-                pub fn $variant(body: Content) -> Content {
+                pub fn $variant($($($name: $ty,)+)? body: Content) -> Content {
                     let span = body.span();
-                    Self::new(PdfMarkerTagKind::$variant, body).pack().spanned(span)
+                    Self {
+                        kind: PdfMarkerTagKind::$variant $(($($name),+))?,
+                        body,
+                    }.pack().spanned(span)
                 }
             )+
         }
@@ -135,6 +148,10 @@ pdf_marker_tag! {
     OutlineBody,
     /// `Figure`
     FigureBody,
+    /// `L` bibliography list
+    Bibliography(numbered: bool),
+    /// `LBody` wrapping `BibEntry`
+    BibEntry,
     /// `Lbl` (marker) of the list item
     ListItemLabel,
     /// `LBody` of the enum item

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

@@ -69,6 +69,20 @@ impl ListCtx {
         item.body = Some(nodes);
     }
 
+    pub(crate) fn push_bib_entry(&mut self, nodes: Vec<TagNode>) {
+        let nodes = vec![TagNode::Group(TagKind::BibEntry.into(), nodes)];
+        // Bibliography lists cannot be nested, but may be missing labels.
+        if let Some(item) = self.items.last_mut().filter(|item| item.body.is_none()) {
+            item.body = Some(nodes);
+        } else {
+            self.items.push(ListItem {
+                label: Vec::new(),
+                body: Some(nodes),
+                sub_list: None,
+            });
+        }
+    }
+
     pub(crate) fn build_list(self, mut nodes: Vec<TagNode>) -> TagNode {
         for item in self.items.into_iter() {
             nodes.push(TagNode::Group(

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

@@ -65,6 +65,16 @@ pub(crate) fn handle_start(
                 return Ok(());
             }
             PdfMarkerTagKind::FigureBody => TagKind::Figure.into(),
+            PdfMarkerTagKind::Bibliography(numbered) => {
+                let numbering =
+                    if numbered { ListNumbering::Decimal } else { ListNumbering::None };
+                push_stack(gc, loc, StackEntryKind::List(ListCtx::new(numbering)))?;
+                return Ok(());
+            }
+            PdfMarkerTagKind::BibEntry => {
+                push_stack(gc, loc, StackEntryKind::BibEntry)?;
+                return Ok(());
+            }
             PdfMarkerTagKind::ListItemLabel => {
                 push_stack(gc, loc, StackEntryKind::ListItemLabel)?;
                 return Ok(());
@@ -225,6 +235,11 @@ pub(crate) fn handle_end(gc: &mut GlobalContext, surface: &mut Surface, loc: Loc
             list_ctx.push_body(entry.nodes);
             return;
         }
+        StackEntryKind::BibEntry => {
+            let list_ctx = gc.tags.stack.parent_list().expect("parent list");
+            list_ctx.push_bib_entry(entry.nodes);
+            return;
+        }
         StackEntryKind::Link(_, link) => {
             let alt = link.alt.as_ref().map(EcoString::to_string);
             let tag = TagKind::Link.with_alt_text(alt);
@@ -507,6 +522,7 @@ pub(crate) enum StackEntryKind {
     List(ListCtx),
     ListItemLabel,
     ListItemBody,
+    BibEntry,
     Link(LinkId, Packed<LinkMarker>),
     /// The footnote reference in the text.
     FootNoteRef,