From df6e347bc55bdcbf370645442290198c0bcdd3fe Mon Sep 17 00:00:00 2001
From: Leedehai <18319900+Leedehai@users.noreply.github.com>
Date: Tue, 4 Jun 2024 11:30:43 -0400
Subject: [PATCH] Align point and linebreak should not increase math row height
 (#4306)

---
 crates/typst/src/math/row.rs                    |  16 ++++++++++++++--
 ...-4187-alignment-point-affects-row-height.png | Bin 0 -> 282 bytes
 tests/suite/math/equation.typ                   |  10 ++++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 tests/ref/issue-4187-alignment-point-affects-row-height.png

diff --git a/crates/typst/src/math/row.rs b/crates/typst/src/math/row.rs
index 0681752ac..cb909b0bc 100644
--- a/crates/typst/src/math/row.rs
+++ b/crates/typst/src/math/row.rs
@@ -117,11 +117,19 @@ impl MathRun {
     }
 
     pub fn ascent(&self) -> Abs {
-        self.iter().map(MathFragment::ascent).max().unwrap_or_default()
+        self.iter()
+            .filter(|e| affects_row_height(e))
+            .map(|e| e.ascent())
+            .max()
+            .unwrap_or_default()
     }
 
     pub fn descent(&self) -> Abs {
-        self.iter().map(MathFragment::descent).max().unwrap_or_default()
+        self.iter()
+            .filter(|e| affects_row_height(e))
+            .map(|e| e.descent())
+            .max()
+            .unwrap_or_default()
     }
 
     pub fn class(&self) -> MathClass {
@@ -386,3 +394,7 @@ impl MathRunFrameBuilder {
         frame
     }
 }
+
+fn affects_row_height(fragment: &MathFragment) -> bool {
+    !matches!(fragment, MathFragment::Align | MathFragment::Linebreak)
+}
diff --git a/tests/ref/issue-4187-alignment-point-affects-row-height.png b/tests/ref/issue-4187-alignment-point-affects-row-height.png
new file mode 100644
index 0000000000000000000000000000000000000000..63a5768b7c41a90ca76d04d0fc7ae7beebdc23cc
GIT binary patch
literal 282
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zE4Q@*!Z?=nabcK1#_nBwKK^@t|Ns9n%wWd`R-e-Qvb?WA3e_$>+MTdr*~UDn8I7ja
zcVn-HSpU^y3ON6$IIP^dI-#veQzZLb#Qog44#M5Lz23FS9Lp_q|9SU7vdPAZu=kOB
zcbXSO+0;JD{A+2RnfP(-&hE4|$KO7lT`cB*-=S1~G2<Mi!#5vs=C)pDJM_qQUb(k8
zZ_ClAbIa$R=WjVG{QQmKe5dMe!)S%=;`tF<#J4`lVr>q#J{a=+?ZsP}P@i~;F*9&Z
V>te2)>SYV^w5O||%Q~loCIDKDdKLfx

literal 0
HcmV?d00001

diff --git a/tests/suite/math/equation.typ b/tests/suite/math/equation.typ
index e7ae677e0..2345de549 100644
--- a/tests/suite/math/equation.typ
+++ b/tests/suite/math/equation.typ
@@ -256,6 +256,16 @@ $ q &= sum_k ln A \
   ],
 )
 
+--- issue-4187-alignment-point-affects-row-height ---
+// In this bug, a row of "-" only should have a very small height; but
+// after adding an alignment point "&", the row gains a larger height.
+// We need to test alignment point "&" does not affect a row's height.
+#box($ - - $, fill: silver)
+#box($ - - $, fill: silver) \
+#box($ a \ - - $, fill: silver)
+#box($ &- - \ &a $, fill: silver)
+#box($ &a \ &- - $, fill: silver)
+
 --- issue-numbering-hint ---
 // In this bug, the hint and error messages for an equation
 // being reference mentioned that it was a "heading" and was