From 02b16bf9cfd2f0dc095055487434a94a63485eeb Mon Sep 17 00:00:00 2001
From: Malo <57839069+MDLC01@users.noreply.github.com>
Date: Thu, 25 Jan 2024 16:14:12 +0100
Subject: [PATCH] Make `math.class` affect the limit configuration (#3231)

---
 crates/typst/src/math/attach.rs |   9 +++++++++
 crates/typst/src/math/class.rs  |   8 ++++++--
 tests/ref/math/class.png        | Bin 6460 -> 7599 bytes
 tests/typ/math/class.typ        |  12 +++++++++++-
 4 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/crates/typst/src/math/attach.rs b/crates/typst/src/math/attach.rs
index ff66a3867..09541d1ca 100644
--- a/crates/typst/src/math/attach.rs
+++ b/crates/typst/src/math/attach.rs
@@ -212,6 +212,15 @@ impl Limits {
         }
     }
 
+    /// The default limit configuration for a math class.
+    pub fn for_class(class: MathClass) -> Self {
+        match class {
+            MathClass::Large => Self::Display,
+            MathClass::Relation => Self::Always,
+            _ => Self::Never,
+        }
+    }
+
     /// Whether limits should be displayed in this context
     pub fn active(&self, ctx: &MathContext) -> bool {
         match self {
diff --git a/crates/typst/src/math/class.rs b/crates/typst/src/math/class.rs
index 9f430ad70..1b6c638ca 100644
--- a/crates/typst/src/math/class.rs
+++ b/crates/typst/src/math/class.rs
@@ -2,12 +2,15 @@ use unicode_math_class::MathClass;
 
 use crate::diag::SourceResult;
 use crate::foundations::{elem, Content, Packed};
-use crate::math::{LayoutMath, MathContext};
+use crate::math::{LayoutMath, Limits, MathContext};
 
 /// Forced use of a certain math class.
 ///
 /// This is useful to treat certain symbols as if they were of a different
-/// class, e.g. to make a symbol behave like a relation.
+/// class, e.g. to make a symbol behave like a relation. The class of a symbol
+/// defines the way it is laid out, including spacing around it, and how its
+/// scripts are attached by default. Note that the latter can always be
+/// overridden using [`{limits}`](math.limits) and [`{scripts}`](math.scripts).
 ///
 /// # Example
 /// ```example
@@ -37,6 +40,7 @@ impl LayoutMath for Packed<ClassElem> {
         ctx.unstyle();
 
         fragment.set_class(*self.class());
+        fragment.set_limits(Limits::for_class(*self.class()));
         ctx.push(fragment);
         Ok(())
     }
diff --git a/tests/ref/math/class.png b/tests/ref/math/class.png
index 27844ebe1410d073e4d759be47849a835ef57f3a..a54dbd673fe5735eb3553c72f7b73fbd1807b6e1 100644
GIT binary patch
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diff --git a/tests/typ/math/class.typ b/tests/typ/math/class.typ
index 0c9fa32b4..a5901b31d 100644
--- a/tests/typ/math/class.typ
+++ b/tests/typ/math/class.typ
@@ -34,4 +34,14 @@ $ a pluseq 5 $
 
 ---
 // Test exceptions.
-$ sqrt(3)\/2 quad d_0.d_1d_2 dots $
\ No newline at end of file
+$ sqrt(3)\/2 quad d_0.d_1d_2 dots $
+
+---
+// Test if the math class changes the limit configuration.
+$ class("normal", ->)_a $
+$class("relation", x)_a$
+$ class("large", x)_a $
+$class("large", ->)_a$
+
+$limits(class("normal", ->))_a$
+$ scripts(class("relation", x))_a $