From a980b29c490a18d28c7d21b6172b82a61dda042a Mon Sep 17 00:00:00 2001
From: Botond Ballo <botond@mozilla.com>
Date: Wed, 16 Oct 2019 21:01:16 +0000
Subject: [PATCH] Bug 1589204 - Fix a bug in Matrix4x4Flagged::operator*.
 r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D49486

--HG--
extra : moz-landing-system : lando
---
 gfx/2d/Matrix.h                | 2 +-
 gfx/tests/gtest/TestMatrix.cpp | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/gfx/2d/Matrix.h b/gfx/2d/Matrix.h
index a80461384461..68830c9e49cb 100644
--- a/gfx/2d/Matrix.h
+++ b/gfx/2d/Matrix.h
@@ -2150,7 +2150,7 @@ class Matrix4x4TypedFlagged
       matrix._14 = _11 * aMatrix._14 + _12 * aMatrix._24;
       matrix._24 = _21 * aMatrix._14 + _22 * aMatrix._24;
       matrix._34 = aMatrix._34;
-      matrix._44 = _41 * aMatrix._14 + _42 * aMatrix._24;
+      matrix._44 = _41 * aMatrix._14 + _42 * aMatrix._24 + aMatrix._44;
       matrix.Analyze();
       return matrix;
     }
diff --git a/gfx/tests/gtest/TestMatrix.cpp b/gfx/tests/gtest/TestMatrix.cpp
index bc2f9e63cd2e..919e81a54c8d 100644
--- a/gfx/tests/gtest/TestMatrix.cpp
+++ b/gfx/tests/gtest/TestMatrix.cpp
@@ -59,3 +59,12 @@ TEST(Matrix, TransformAndClipRect)
   EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(150, 50, 100, 200), c))
                   .IsEqualInterior(Rect(150, 100, 50, 100)));
 }
+
+TEST(Matrix4x4Flagged, Mult)
+{
+  Matrix4x4Flagged a = Matrix4x4::Translation(Point(42, 42));
+  Matrix4x4 b = Matrix4x4::Scaling(2, 2, 1);
+  Matrix4x4Flagged actual = a * b;
+  Matrix4x4Flagged expected(2, 0, 0, 0, 0, 2, 0, 0, 0, 0, 1, 0, 84, 84, 0, 1);
+  EXPECT_EQ(expected, actual);
+}
\ No newline at end of file