From 578ba640f3666b5dc309ec0a03d6f6d5f2ae14a2 Mon Sep 17 00:00:00 2001
From: Max <me@mkor.je>
Date: Wed, 27 Nov 2024 11:16:25 +0000
Subject: [PATCH] Fix weak spacing being ignored unconditionally in `math.lr`
 (#5477)

---
 crates/typst-layout/src/math/lr.rs |  14 +++++++++++---
 tests/ref/math-lr-weak-spacing.png | Bin 647 -> 1171 bytes
 tests/suite/math/delimited.typ     |   1 +
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/crates/typst-layout/src/math/lr.rs b/crates/typst-layout/src/math/lr.rs
index d195e67d..01a7f4cc 100644
--- a/crates/typst-layout/src/math/lr.rs
+++ b/crates/typst-layout/src/math/lr.rs
@@ -62,7 +62,7 @@ pub fn layout_lr(
     }
 
     // Handle MathFragment::Variant fragments that should be scaled up.
-    for fragment in inner_fragments {
+    for fragment in inner_fragments.iter_mut() {
         if let MathFragment::Variant(ref mut variant) = fragment {
             if variant.mid_stretched == Some(false) {
                 variant.mid_stretched = Some(true);
@@ -74,10 +74,18 @@ pub fn layout_lr(
     // Remove weak SpacingFragment immediately after the opening or immediately
     // before the closing.
     let mut index = 0;
+    let opening_exists = inner_fragments
+        .first()
+        .is_some_and(|f| f.class() == MathClass::Opening);
+    let closing_exists = inner_fragments
+        .last()
+        .is_some_and(|f| f.class() == MathClass::Closing);
     fragments.retain(|fragment| {
+        let discard = (index == start_idx + 1 && opening_exists
+            || index + 2 == end_idx && closing_exists)
+            && matches!(fragment, MathFragment::Spacing(_, true));
         index += 1;
-        (index != start_idx + 2 && index + 1 != end_idx)
-            || !matches!(fragment, MathFragment::Spacing(_, true))
+        !discard
     });
 
     ctx.extend(fragments);
diff --git a/tests/ref/math-lr-weak-spacing.png b/tests/ref/math-lr-weak-spacing.png
index 871aaa2ebaae745a58eca5693ff7251a5ebee37c..2478ca2a3dd281a756ea9580786b9c360109eb81 100644
GIT binary patch
delta 1164
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delta 635
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diff --git a/tests/suite/math/delimited.typ b/tests/suite/math/delimited.typ
index fc00333d..22674050 100644
--- a/tests/suite/math/delimited.typ
+++ b/tests/suite/math/delimited.typ
@@ -87,6 +87,7 @@ $ 1/(2 y (x) (2(3)) $
 // Test ignoring weak spacing immediately after the opening
 // and immediately before the closing.
 $ [#h(1em, weak: true)A(dif x, f(x) dif x)sum#h(1em, weak: true)] $
+$ lr(\[#h(1em, weak: true)lr(A dif x, f(x) dif x\))sum#h(1em, weak:true)a) $
 
 --- math-lr-nested ---
 // Test nested lr calls.