From 60f1d8f9b5f7c11eade2573eea39cfd656509eed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michael=20F=C3=A4rber?= <01mf02@gmail.com>
Date: Wed, 4 Dec 2024 17:55:37 +0100
Subject: [PATCH] Prepend section numbers to headings in HTML output. (#5522)

---
 crates/typst-library/src/model/heading.rs | 46 +++++++++++------------
 1 file changed, 22 insertions(+), 24 deletions(-)

diff --git a/crates/typst-library/src/model/heading.rs b/crates/typst-library/src/model/heading.rs
index eb3c5413a..fc0e4ad25 100644
--- a/crates/typst-library/src/model/heading.rs
+++ b/crates/typst-library/src/model/heading.rs
@@ -217,21 +217,7 @@ 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> {
-        if TargetElem::target_in(styles).is_html() {
-            // HTML's h1 is closer to a title element. There should only be one.
-            // Meanwhile, a level 1 Typst heading is a section heading. For this
-            // reason, levels are offset by one: A Typst level 1 heading becomes
-            // a `<h2>`.
-            let level = self.resolve_level(styles);
-            let t = [tag::h2, tag::h3, tag::h4, tag::h5, tag::h6][level.get().min(5) - 1];
-
-            // TODO: Don't ignore the various non-body properties.
-            let body = self.body().clone();
-            return Ok(HtmlElem::new(t)
-                .with_body(Some(body))
-                .pack()
-                .spanned(self.span()));
-        }
+        let html = TargetElem::target_in(styles).is_html();
 
         const SPACING_TO_NUMBERING: Em = Em::new(0.3);
 
@@ -250,7 +236,7 @@ impl Show for Packed<HeadingElem> {
                 .display_at_loc(engine, location, styles, numbering)?
                 .spanned(span);
 
-            if hanging_indent.is_auto() {
+            if hanging_indent.is_auto() && !html {
                 let pod = Region::new(Axes::splat(Abs::inf()), Axes::splat(false));
 
                 // We don't have a locator for the numbering here, so we just
@@ -268,19 +254,31 @@ impl Show for Packed<HeadingElem> {
                 indent = size.x + SPACING_TO_NUMBERING.resolve(styles);
             }
 
-            realized = numbering
-                + HElem::new(SPACING_TO_NUMBERING.into()).with_weak(true).pack()
-                + realized;
+            let spacing = if html {
+                SpaceElem::shared().clone()
+            } else {
+                HElem::new(SPACING_TO_NUMBERING.into()).with_weak(true).pack()
+            };
+
+            realized = numbering + spacing + realized;
         }
 
-        if indent != Abs::zero() {
+        if indent != Abs::zero() && !html {
             realized = realized.styled(ParElem::set_hanging_indent(indent.into()));
         }
 
-        Ok(BlockElem::new()
-            .with_body(Some(BlockBody::Content(realized)))
-            .pack()
-            .spanned(span))
+        Ok(if html {
+            // HTML's h1 is closer to a title element. There should only be one.
+            // Meanwhile, a level 1 Typst heading is a section heading. For this
+            // reason, levels are offset by one: A Typst level 1 heading becomes
+            // a `<h2>`.
+            let level = self.resolve_level(styles);
+            let t = [tag::h2, tag::h3, tag::h4, tag::h5, tag::h6][level.get().min(5) - 1];
+            HtmlElem::new(t).with_body(Some(realized)).pack().spanned(span)
+        } else {
+            let realized = BlockBody::Content(realized);
+            BlockElem::new().with_body(Some(realized)).pack().spanned(span)
+        })
     }
 }