1 files changed, 86 insertions, 0 deletions
diff --git a/crates/typst-library/src/meta/document.rs b/crates/typst-library/src/meta/document.rs
new file mode 100644
index 00000000..db036e0a
--- /dev/null
+++ b/crates/typst-library/src/meta/document.rs
@@ -0,0 +1,86 @@
+use crate::layout::{LayoutRoot, PageElem};
+use crate::prelude::*;
+
+/// The root element of a document and its metadata.
+///
+/// All documents are automatically wrapped in a `document` element. You cannot
+/// create a document element yourself. This function is only used with
+/// [set rules]($styling/#set-rules) to specify document metadata. Such a set
+/// rule must appear before any of the document's contents.
+///
+/// ```example
+/// #set document(title: "Hello")
+///
+/// This has no visible output, but
+/// embeds metadata into the PDF!
+/// ```
+///
+/// Note that metadata set with this function is not rendered within the
+/// document. Instead, it is embedded in the compiled PDF file.
+///
+/// Display: Document
+/// Category: meta
+#[element(Construct, LayoutRoot)]
+pub struct DocumentElem {
+    /// The document's title. This is often rendered as the title of the
+    /// PDF viewer window.
+    pub title: Option<EcoString>,
+
+    /// The document's authors.
+    pub author: Author,
+
+    /// The page runs.
+    #[internal]
+    #[variadic]
+    pub children: Vec<Content>,
+}
+
+impl Construct for DocumentElem {
+    fn construct(_: &mut Vm, args: &mut Args) -> SourceResult<Content> {
+        bail!(args.span, "can only be used in set rules")
+    }
+}
+
+impl LayoutRoot for DocumentElem {
+    /// Layout the document into a sequence of frames, one per page.
+    #[tracing::instrument(name = "DocumentElem::layout_root", skip_all)]
+    fn layout_root(&self, vt: &mut Vt, styles: StyleChain) -> SourceResult<Document> {
+        tracing::info!("Document layout");
+
+        let mut pages = vec![];
+
+        for mut child in &self.children() {
+            let outer = styles;
+            let mut styles = styles;
+            if let Some((elem, local)) = child.to_styled() {
+                styles = outer.chain(local);
+                child = elem;
+            }
+
+            if let Some(page) = child.to::<PageElem>() {
+                let number = NonZeroUsize::ONE.saturating_add(pages.len());
+                let fragment = page.layout(vt, styles, number)?;
+                pages.extend(fragment);
+            } else {
+                bail!(child.span(), "unexpected document child");
+            }
+        }
+
+        Ok(Document {
+            pages,
+            title: self.title(styles),
+            author: self.author(styles).0,
+        })
+    }
+}
+
+/// A list of authors.
+#[derive(Debug, Default, Clone, Hash)]
+pub struct Author(Vec<EcoString>);
+
+cast! {
+    Author,
+    self => self.0.into_value(),
+    v: EcoString => Self(vec![v]),
+    v: Array => Self(v.into_iter().map(Value::cast).collect::<StrResult<_>>()?),
+}