From 043442e21b882b778e43f8fcdd570ec9fea4adf2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Antonio=20S=C3=A1nchez?= <cantonios@google.com>
Date: Tue, 30 Jan 2024 06:37:33 +0000
Subject: [PATCH] Fix preshear transformation.

---
 Eigen/src/Geometry/Transform.h | 3 ++-
 test/geo_transformations.cpp   | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Geometry/Transform.h b/Eigen/src/Geometry/Transform.h
index 077441da8..fd3fc58f4 100644
--- a/Eigen/src/Geometry/Transform.h
+++ b/Eigen/src/Geometry/Transform.h
@@ -943,7 +943,8 @@ EIGEN_DEVICE_FUNC Transform<Scalar, Dim, Mode, Options>& Transform<Scalar, Dim,
     const Scalar& sx, const Scalar& sy) {
   EIGEN_STATIC_ASSERT(int(Dim) == 2, YOU_MADE_A_PROGRAMMING_MISTAKE)
   EIGEN_STATIC_ASSERT(Mode != int(Isometry), THIS_METHOD_IS_ONLY_FOR_SPECIFIC_TRANSFORMATIONS)
-  m_matrix.template block<Dim, HDim>(0, 0) = LinearMatrixType(1, sx, sy, 1) * m_matrix.template block<Dim, HDim>(0, 0);
+  m_matrix.template block<Dim, HDim>(0, 0) =
+      LinearMatrixType({{1, sy}, {sx, 1}}) * m_matrix.template block<Dim, HDim>(0, 0);
   return *this;
 }
 
diff --git a/test/geo_transformations.cpp b/test/geo_transformations.cpp
index 2fddf55cc..a9eb87e25 100644
--- a/test/geo_transformations.cpp
+++ b/test/geo_transformations.cpp
@@ -273,6 +273,12 @@ void transformations() {
              .matrix()
              .isIdentity(test_precision<Scalar>()));
 
+  t20.setIdentity();
+  t20.shear(Scalar(2), Scalar(3));
+  Transform2 t23 = t20 * t21;
+  t21.preshear(Scalar(2), Scalar(3));
+  VERIFY_IS_APPROX(t21, t23);
+
   // Transform - new API
   // 3D
   t0.setIdentity();