From 22a16ccee7e3419743e6693b350ffaacf690690f Mon Sep 17 00:00:00 2001
From: Jeremy Chen <jeremychen@mozilla.com>
Date: Wed, 19 Jul 2017 17:02:46 +0800
Subject: [PATCH] stylo: Fix Y scale computation while decomposing a 3D matrix.

While decomposing a 3D matrix, we should normalize the 2nd row right after the
Y scale computation. However, we accidentally use the length of the 1st row to
do the normalization. This causes the wrong Scale3D function while decomposing,
and then leads to the wrong decomposed 3D matrix.

Here, we correct it by using the right value (the length of the 2nd row).

r=hiro https://bugzilla.mozilla.org/show_bug.cgi?id=1381196
---
 components/style/properties/helpers/animated_properties.mako.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/components/style/properties/helpers/animated_properties.mako.rs b/components/style/properties/helpers/animated_properties.mako.rs
index 21c0b25fa018..c216201dafc8 100644
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@@ -2146,7 +2146,7 @@ fn decompose_3d_matrix(mut matrix: ComputedMatrix) -> Result<MatrixDecomposed3D,
     row[1] = combine(row[1], row[0], 1.0, -skew.0);
 
     // Now, compute Y scale and normalize 2nd row.
-    let row1len = (row[0][0] * row[0][0] + row[0][1] * row[0][1] + row[0][2] * row[0][2]).sqrt();
+    let row1len = (row[1][0] * row[1][0] + row[1][1] * row[1][1] + row[1][2] * row[1][2]).sqrt();
     scale.1 = row1len;
     row[1] = [row[1][0] / row1len, row[1][1] / row1len, row[1][2] / row1len];
     skew.0 /= scale.1;