Indent configuration for multiline headings

crates/typst/src/model/heading.rs

@@ -3,12 +3,14 @@ use std::num::NonZeroUsize;
 use crate::diag::SourceResult;
 use crate::engine::Engine;
 use crate::foundations::{
- elem, Content, NativeElement, Packed, Show, ShowSet, Smart, StyleChain, Styles,
- Synthesize,
+ elem, Content, NativeElement, Packed, Resolve, Show, ShowSet, Smart, StyleChain,
+ Styles, Synthesize,
 };
 use crate::introspection::{Count, Counter, CounterUpdate, Locatable};
-use crate::layout::{BlockElem, Em, HElem, VElem};
-use crate::model::{Numbering, Outlinable, Refable, Supplement};
+use crate::layout::{
+ Abs, Axes, BlockElem, Em, HElem, LayoutMultiple, Length, Regions, VElem,
+};
+use crate::model::{Numbering, Outlinable, ParElem, Refable, Supplement};
 use crate::text::{FontWeight, LocalName, SpaceElem, TextElem, TextSize};
 use crate::util::NonZeroExt;
 
@@ -163,6 +165,18 @@ pub struct HeadingElem {
  #[default(Smart::Auto)]
  pub bookmarked: Smart<bool>,
 
+ /// The indent all but the first line of a heading should have.
+ ///
+ /// The default value of `{auto}` indicates that the subsequent heading
+ /// lines will be indented based on the width of the numbering.
+ ///
+ /// ```example
+ /// #set heading(numbering: "1.")
+ /// #heading[A very, very, very, very, very, very long heading]
+ /// ```
+ #[default(Smart::Auto)]
+ pub hanging_indent: Smart<Length>,
+
  /// The heading's title.
  #[required]
  pub body: Content,
@@ -201,15 +215,39 @@ impl Synthesize for Packed<HeadingElem> {
 impl Show for Packed<HeadingElem> {
  #[typst_macros::time(name = "heading", span = self.span())]
  fn show(&self, engine: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
+ const SPACING_TO_NUMBERING: Em = Em::new(0.3);
+
  let span = self.span();
  let mut realized = self.body().clone();
+
+ let hanging_indent = self.hanging_indent(styles);
+
+ let mut indent = match hanging_indent {
+ Smart::Custom(length) => length.resolve(styles),
+ Smart::Auto => Abs::zero(),
+ };
+
  if let Some(numbering) = (**self).numbering(styles).as_ref() {
- realized = Counter::of(HeadingElem::elem())
+ let numbering = Counter::of(HeadingElem::elem())
  .display_at_loc(engine, self.location().unwrap(), styles, numbering)?
- .spanned(span)
- + HElem::new(Em::new(0.3).into()).with_weak(true).pack()
+ .spanned(span);
+
+ if hanging_indent.is_auto() {
+ let pod = Regions::one(Axes::splat(Abs::inf()), Axes::splat(false));
+ let size = numbering.measure(engine, styles, pod)?.into_frame().size();
+
+ indent = size.x + SPACING_TO_NUMBERING.resolve(styles);
+ }
+
+ realized = numbering
+ + HElem::new(SPACING_TO_NUMBERING.into()).with_weak(true).pack()
  + realized;
  }
+
+ if indent != Abs::zero() {
+ realized = realized.styled(ParElem::set_hanging_indent(indent.into()));
+ }
+
  Ok(BlockElem::new().with_body(Some(realized)).pack().spanned(span))
  }
 }