feat: [no ci] mark artifacts

crates/typst-layout/src/pages/finalize.rs

@@ -1,7 +1,10 @@
 use typst_library::diag::SourceResult;
 use typst_library::engine::Engine;
+use typst_library::foundations::{Content, NativeElement};
 use typst_library::introspection::{ManualPageCounter, Tag};
-use typst_library::layout::{Frame, FrameItem, Page, Point};
+use typst_library::layout::{
+    ArtifactKind, ArtifactMarker, Frame, FrameItem, Page, Point,
+};
 
 use super::LayoutedPage;
 
@@ -45,10 +48,12 @@ pub fn finalize(
     // important as it affects the relative ordering of introspectable elements
     // and thus how counters resolve.
     if let Some(background) = background {
-        frame.push_frame(Point::zero(), background);
+        let tag = ArtifactMarker::new(ArtifactKind::Page).pack();
+        push_tagged(&mut frame, Point::zero(), background, tag);
     }
     if let Some(header) = header {
-        frame.push_frame(Point::with_x(margin.left), header);
+        let tag = ArtifactMarker::new(ArtifactKind::Page).pack();
+        push_tagged(&mut frame, Point::with_x(margin.left), header, tag);
     }
 
     // Add the inner contents.
@@ -57,7 +62,8 @@ pub fn finalize(
     // Add the "after" marginals.
     if let Some(footer) = footer {
         let y = frame.height() - footer.height();
-        frame.push_frame(Point::new(margin.left, y), footer);
+        let tag = ArtifactMarker::new(ArtifactKind::Footer).pack();
+        push_tagged(&mut frame, Point::new(margin.left, y), footer, tag);
     }
     if let Some(foreground) = foreground {
         frame.push_frame(Point::zero(), foreground);
@@ -72,3 +78,13 @@ pub fn finalize(
 
     Ok(Page { frame, fill, numbering, supplement, number })
 }
+
+fn push_tagged(frame: &mut Frame, mut pos: Point, inner: Frame, tag: Content) {
+    frame.push(pos, FrameItem::Tag(Tag::Start(tag)));
+
+    frame.push_frame(pos, inner);
+
+    pos.y += inner.height();
+    let loc = tag.location().unwrap();
+    frame.push(pos, FrameItem::Tag(Tag::End(loc, key)))
+}

crates/typst-layout/src/pages/run.rs

@@ -185,8 +185,6 @@ fn layout_page_run_impl(
     )?;
 
     // Layouts a single marginal.
-    // TODO: add some sort of tag that indicates the marginals and use it to
-    // mark them as artifacts for PDF/UA.
     let mut layout_marginal = |content: &Option<Content>, area, align| {
         let Some(content) = content else { return Ok(None) };
         let aligned = content.clone().styled(AlignElem::set_alignment(align));

crates/typst-library/src/layout/page.rs

@@ -10,7 +10,7 @@ use crate::foundations::{
     cast, elem, Args, AutoValue, Cast, Construct, Content, Dict, Fold, NativeElement,
     Set, Smart, Value,
 };
-use crate::introspection::Introspector;
+use crate::introspection::{Introspector, Locatable};
 use crate::layout::{
     Abs, Alignment, FlushElem, Frame, HAlignment, Length, OuterVAlignment, Ratio, Rel,
     Sides, SpecificAlignment,
@@ -451,6 +451,28 @@ impl PagebreakElem {
     }
 }
 
+// HACK: this should probably not be an element
+#[derive(Copy)]
+#[elem(Construct, Locatable)]
+pub struct ArtifactMarker {
+    #[internal]
+    #[required]
+    pub kind: ArtifactKind,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum ArtifactKind {
+    Header,
+    Footer,
+    Page,
+}
+
+impl Construct for ArtifactMarker {
+    fn construct(_: &mut Engine, args: &mut Args) -> SourceResult<Content> {
+        bail!(args.span, "cannot be constructed manually");
+    }
+}
+
 /// A finished document with metadata and page frames.
 #[derive(Debug, Default, Clone)]
 pub struct PagedDocument {

crates/typst-pdf/src/convert.rs

@@ -31,7 +31,7 @@ use crate::metadata::build_metadata;
 use crate::outline::build_outline;
 use crate::page::PageLabelExt;
 use crate::shape::handle_shape;
-use crate::tags::{handle_close_tag, handle_open_tag, Placeholder, TagNode, Tags};
+use crate::tags::{self, Placeholder, TagNode, Tags};
 use crate::text::handle_text;
 use crate::util::{convert_path, display_font, AbsExt, TransformExt};
 use crate::PdfOptions;
@@ -114,18 +114,7 @@ fn convert_pages(gc: &mut GlobalContext, document: &mut Document) -> SourceResul
             let mut surface = page.surface();
             let mut fc = FrameContext::new(typst_page.frame.size());
 
-            // Marked-content may not cross page boundaries: reopen tag
-            // that was closed at the end of the last page.
-            if let Some((_, _, nodes)) = gc.tags.stack.last_mut() {
-                let tag = if gc.tags.in_artifact {
-                    ContentTag::Artifact(ArtifactType::Other)
-                } else {
-                    ContentTag::Other
-                };
-                // TODO: somehow avoid empty marked-content sequences
-                let id = surface.start_tagged(tag);
-                nodes.push(TagNode::Leaf(id));
-            }
+            tags::restart(gc, &mut surface);
 
             handle_frame(
                 &mut fc,
@@ -135,17 +124,11 @@ fn convert_pages(gc: &mut GlobalContext, document: &mut Document) -> SourceResul
                 gc,
             )?;
 
-            // Marked-content may not cross page boundaries: close open tag.
-            if !gc.tags.stack.is_empty() {
-                surface.end_tagged();
-            }
+            tags::end_open(gc, &mut surface);
 
             surface.finish();
 
-            for (placeholder, annotation) in fc.annotations {
-                let annotation_id = page.add_tagged_annotation(annotation);
-                gc.tags.init_placeholder(placeholder, Node::Leaf(annotation_id));
-            }
+            tags::add_annotations(gc, &mut page, fc.annotations);
         }
     }
 
@@ -318,10 +301,10 @@ pub(crate) fn handle_frame(
                 handle_link(fc, gc, alt.as_ref().map(EcoString::to_string), dest, *size)
             }
             FrameItem::Tag(introspection::Tag::Start(elem)) => {
-                handle_open_tag(gc, surface, elem)
+                tags::handle_start(gc, surface, elem)
             }
             FrameItem::Tag(introspection::Tag::End(loc, _)) => {
-                handle_close_tag(gc, surface, loc);
+                tags::handle_end(gc, surface, loc);
             }
         }
 

crates/typst-pdf/src/tags.rs

@@ -1,9 +1,15 @@
 use std::cell::OnceCell;
+use std::ops::Deref;
 
+use krilla::annotation::Annotation;
+use krilla::page::Page;
 use krilla::surface::Surface;
-use krilla::tagging::{ContentTag, Identifier, Node, Tag, TagGroup, TagTree};
+use krilla::tagging::{
+    ArtifactType, ContentTag, Identifier, Node, Tag, TagGroup, TagTree,
+};
 use typst_library::foundations::{Content, StyleChain};
 use typst_library::introspection::Location;
+use typst_library::layout::{ArtifactKind, ArtifactMarker};
 use typst_library::model::{HeadingElem, OutlineElem, OutlineEntry};
 
 use crate::convert::GlobalContext;
@@ -12,7 +18,7 @@ pub(crate) struct Tags {
     /// The intermediary stack of nested tag groups.
     pub(crate) stack: Vec<(Location, Tag, Vec<TagNode>)>,
     pub(crate) placeholders: Vec<OnceCell<Node>>,
-    pub(crate) in_artifact: bool,
+    pub(crate) in_artifact: Option<(Location, ArtifactMarker)>,
 
     /// The output.
     pub(crate) tree: Vec<TagNode>,
@@ -34,7 +40,7 @@ impl Tags {
         Self {
             stack: Vec::new(),
             placeholders: Vec::new(),
-            in_artifact: false,
+            in_artifact: None,
 
             tree: Vec::new(),
         }
@@ -142,16 +148,61 @@ impl Tags {
     }
 }
 
-pub(crate) fn handle_open_tag(
+/// Marked-content may not cross page boundaries: restart tag that was still open
+/// at the end of the last page.
+pub(crate) fn restart(gc: &mut GlobalContext, surface: &mut Surface) {
+    // TODO: somehow avoid empty marked-content sequences
+    if let Some((_, marker)) = gc.tags.in_artifact {
+        let ty = artifact_type(marker.kind);
+        surface.start_tagged(ContentTag::Artifact(ty));
+    } else if let Some((_, _, nodes)) = gc.tags.stack.last_mut() {
+        let id = surface.start_tagged(ContentTag::Other);
+        nodes.push(TagNode::Leaf(id));
+    }
+}
+
+/// Marked-content may not cross page boundaries: end any open tag.
+pub(crate) fn end_open(gc: &mut GlobalContext, surface: &mut Surface) {
+    if !gc.tags.stack.is_empty() || gc.tags.in_artifact.is_some() {
+        surface.end_tagged();
+    }
+}
+
+/// Add all annotations that were found in the page frame.
+pub(crate) fn add_annotations(
+    gc: &mut GlobalContext,
+    page: &mut Page,
+    annotations: Vec<(Placeholder, Annotation)>,
+) {
+    for (placeholder, annotation) in annotations {
+        let annotation_id = page.add_tagged_annotation(annotation);
+        gc.tags.init_placeholder(placeholder, Node::Leaf(annotation_id));
+    }
+}
+
+pub(crate) fn handle_start(
     gc: &mut GlobalContext,
     surface: &mut Surface,
     elem: &Content,
 ) {
-    if gc.tags.in_artifact {
+    if gc.tags.in_artifact.is_some() {
+        // Don't nest artifacts
         return;
     }
 
-    let Some(loc) = elem.location() else { return };
+    let loc = elem.location().unwrap();
+
+    if let Some(marker) = elem.to_packed::<ArtifactMarker>() {
+        if !gc.tags.stack.is_empty() {
+            surface.end_tagged();
+        }
+
+        let marker = *marker.deref();
+        let ty = artifact_type(marker.kind);
+        surface.start_tagged(ContentTag::Artifact(ty));
+        gc.tags.in_artifact = Some((loc, marker));
+        return;
+    }
 
     let tag = if let Some(heading) = elem.to_packed::<HeadingElem>() {
         let level = heading.resolve_level(StyleChain::default());
@@ -186,11 +237,14 @@ pub(crate) fn handle_open_tag(
     gc.tags.stack.push((loc, tag, vec![TagNode::Leaf(content_id)]));
 }
 
-pub(crate) fn handle_close_tag(
-    gc: &mut GlobalContext,
-    surface: &mut Surface,
-    loc: &Location,
-) {
+pub(crate) fn handle_end(gc: &mut GlobalContext, surface: &mut Surface, loc: &Location) {
+    if gc.tags.in_artifact.is_some_and(|(l, _)| l == *loc) {
+        gc.tags.in_artifact = None;
+        surface.end_tagged();
+        restart(gc, surface);
+        return;
+    }
+
     let Some((_, tag, nodes)) = gc.tags.stack.pop_if(|(l, ..)| l == loc) else {
         return;
     };
@@ -207,3 +261,11 @@ pub(crate) fn handle_close_tag(
         gc.tags.tree.push(TagNode::Group(tag, nodes));
     }
 }
+
+fn artifact_type(kind: ArtifactKind) -> ArtifactType {
+    match kind {
+        ArtifactKind::Header => ArtifactType::Header,
+        ArtifactKind::Footer => ArtifactType::Footer,
+        ArtifactKind::Page => ArtifactType::Page,
+    }
+}