From cd1a786539e81c8b83b774289fd16645d740d5de Mon Sep 17 00:00:00 2001
From: Max <max@mkor.je>
Date: Fri, 1 Aug 2025 10:55:37 +0000
Subject: [PATCH] Prevent broken glyph assemblies when font data is incorrect
 (#6688)

---
 crates/typst-layout/src/math/fragment.rs          |   4 +++-
 .../ref/math-stretch-min-overlap-exceeds-max.png  | Bin 0 -> 585 bytes
 tests/suite/math/stretch.typ                      |   9 +++++++++
 3 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 tests/ref/math-stretch-min-overlap-exceeds-max.png

diff --git a/crates/typst-layout/src/math/fragment.rs b/crates/typst-layout/src/math/fragment.rs
index 3497587c..fce0ca30 100644
--- a/crates/typst-layout/src/math/fragment.rs
+++ b/crates/typst-layout/src/math/fragment.rs
@@ -739,7 +739,9 @@ fn assemble(
                 }
 
                 advance -= max_overlap;
-                growable += max_overlap - min_overlap;
+                // In case we have that max_overlap < min_overlap, ensure we
+                // don't decrease the value of growable.
+                growable += (max_overlap - min_overlap).max(Abs::zero());
             }
 
             full += advance;
diff --git a/tests/ref/math-stretch-min-overlap-exceeds-max.png b/tests/ref/math-stretch-min-overlap-exceeds-max.png
new file mode 100644
index 0000000000000000000000000000000000000000..a75437fd960a4dad089f5c72add051e356fc7cb1
GIT binary patch
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diff --git a/tests/suite/math/stretch.typ b/tests/suite/math/stretch.typ
index d145f72a..80015540 100644
--- a/tests/suite/math/stretch.typ
+++ b/tests/suite/math/stretch.typ
@@ -91,3 +91,12 @@ $ body^"text" $
   }
   $body^"long text"$
 }
+
+--- math-stretch-min-overlap-exceeds-max ---
+// Test that glyph assembly doesn't end up with negative lengths if the max
+// overlap calculated is less than the minConnectorOverlap.
+#show math.equation: set text(font: "STIX Two Math")
+// Warning: glyph has assembly parts with overlap less than minConnectorOverlap
+// Hint: its rendering may appear broken - this is probably a font bug
+// Hint: please file an issue at https://github.com/typst/typst/issues
+$ stretch(->)^"Gauss-Jordan Elimination" $