From f699b8cfb265bdd99bf509bce9bd205ce1923c62 Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Mon, 30 Oct 2017 17:03:03 -0700
Subject: [PATCH] Handle animating 2D matrices

---
 .../helpers/animated_properties.mako.rs       | 37 ++++++++++++++-
 components/style/values/computed/transform.rs | 46 ++++++++++++++-----
 2 files changed, 70 insertions(+), 13 deletions(-)

diff --git a/components/style/properties/helpers/animated_properties.mako.rs b/components/style/properties/helpers/animated_properties.mako.rs
index 691b57845da..7563dc3979e 100644
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@@ -44,7 +44,7 @@ use values::computed::{LengthOrPercentageOrNone, MaxLength};
 use values::computed::{NonNegativeNumber, Number, NumberOrPercentage, Percentage};
 use values::computed::length::NonNegativeLengthOrPercentage;
 use values::computed::ToComputedValue;
-use values::computed::transform::{DirectionVector, Matrix3D};
+use values::computed::transform::{DirectionVector, Matrix, Matrix3D};
 use values::generics::transform::{Transform, TransformOperation};
 use values::distance::{ComputeSquaredDistance, SquaredDistance};
 #[cfg(feature = "gecko")] use values::generics::FontSettings as GenericFontSettings;
@@ -1033,7 +1033,14 @@ impl Animate for ComputedTransformOperation {
                     this.animate(other, procedure)?,
                 ))
             },
-            // XXXManishearth handle 2D matrix
+            (
+                &TransformOperation::Matrix(ref this),
+                &TransformOperation::Matrix(ref other),
+            ) => {
+                Ok(TransformOperation::Matrix(
+                    this.animate(other, procedure)?,
+                ))
+            },
             (
                 &TransformOperation::Skew(ref fx, ref fy),
                 &TransformOperation::Skew(ref tx, ref ty),
@@ -1444,6 +1451,32 @@ impl Animate for Matrix3D {
     }
 }
 
+impl Animate for Matrix {
+    #[cfg(feature = "servo")]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        let this = Matrix3D::from(*self);
+        let other = Matrix3D::from(*other);
+        let this = MatrixDecomposed2D::from(this);
+        let other = MatrixDecomposed2D::from(other);
+        Ok(Matrix3D::from(this.animate(&other, procedure)?).into_2d()?)
+    }
+
+    #[cfg(feature = "gecko")]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        let from = decompose_2d_matrix(&(*self).into());
+        let to = decompose_2d_matrix(&(*other).into());
+        match (from, to) {
+            (Ok(from), Ok(to)) => {
+                Matrix3D::from(from.animate(&to, procedure)?).into_2d()
+            },
+            // Matrices can be undecomposable due to couple reasons, e.g.,
+            // non-invertible matrices. In this case, we should report Err here,
+            // and let the caller do the fallback procedure.
+            _ => Err(())
+        }
+    }
+}
+
 impl ComputeSquaredDistance for Matrix3D {
     #[inline]
     #[cfg(feature = "servo")]
diff --git a/components/style/values/computed/transform.rs b/components/style/values/computed/transform.rs
index 4c90a01b3d1..4c909a53585 100644
--- a/components/style/values/computed/transform.rs
+++ b/components/style/values/computed/transform.rs
@@ -63,6 +63,22 @@ impl Matrix3D {
             m41: 0., m42: 0., m43: 0., m44: 1.0
         }
     }
+
+    /// Convert to a 2D Matrix
+    pub fn into_2d(self) -> Result<Matrix, ()> {
+        if self.m13 == 0. && self.m23 == 0. &&
+           self.m31 == 0. && self.m32 == 0. &&
+           self.m33 == 1. && self.m34 == 0. &&
+           self.m14 == 0. && self.m24 == 0. &&
+           self.m43 == 0. && self.m44 == 1. {
+            Ok(Matrix {
+                a: self.m11, c: self.m21, e: self.m41,
+                b: self.m12, d: self.m22, f: self.m42,
+            })
+        } else {
+            Err(())
+        }
+    }
 }
 
 impl PrefixedMatrix3D {
@@ -84,10 +100,21 @@ impl Matrix {
     /// Get an identity matrix
     pub fn identity() -> Self {
         Self {
-            a: 1., c: 0., /* 0 */e: 0.,
-            b: 0., d: 1., /* 0 */f: 0.,
+            a: 1., c: 0., /* 0      0*/
+            b: 0., d: 1., /* 0      0*/
             /* 0      0      1      0 */
-            /* 0      0      0      1 */
+            e: 0., f: 0., /* 0      1 */
+        }
+    }
+}
+
+impl From<Matrix> for Matrix3D {
+    fn from(m: Matrix) -> Self {
+        Self {
+            m11: m.a, m12: m.b, m13: 0.0, m14: 0.0,
+            m21: m.c, m22: m.d, m23: 0.0, m24: 0.0,
+            m31: 0.0, m32: 0.0, m33: 1.0, m34: 0.0,
+            m41: m.e, m42: m.f, m43: 0.0, m44: 1.0
         }
     }
 }
@@ -97,10 +124,10 @@ impl PrefixedMatrix {
     /// Get an identity matrix
     pub fn identity() -> Self {
         Self {
-            a: 1., c: 0., /* 0 */e: Either::First(0.),
-            b: 0., d: 1., /* 0 */f: Either::First(0.),
-            /* 0      0      1      0 */
-            /* 0      0      0      1 */
+            a: 1.,                    c: 0., /*            0      0 */
+            b: 0.,                    d: 1., /*            0      0 */
+            /* 0                      0                    1      0 */
+            e: Either::First(0.), f: Either::First(0.), /* 0      1 */
         }
     }
 }
@@ -240,10 +267,7 @@ impl ToAnimatedZero for TransformOperation {
             GenericTransformOperation::Scale3D(..) => {
                 Ok(GenericTransformOperation::Scale3D(1.0, 1.0, 1.0))
             },
-            GenericTransformOperation::Scale(_, None) => {
-                Ok(GenericTransformOperation::Scale(1.0, None))
-            },
-            GenericTransformOperation::Scale(_, Some(_)) => {
+            GenericTransformOperation::Scale(_, _) => {
                 Ok(GenericTransformOperation::Scale(1.0, Some(1.0)))
             },
             GenericTransformOperation::ScaleX(..) => {