style: Implement ComputeSquaredDistance for individual transforms.

We manually implement ComputeSquaredDistance for Translate, Rotate, and
Scale because we have to handle mismatch cases, and actually we don't
need to implement it for specified types.

Differential Revision: https://phabricator.services.mozilla.com/D11935

components/style/values/animated/transform.rs

@@ -1309,19 +1309,8 @@ impl ComputeSquaredDistance for ComputedTransformOperation {
                 &TransformOperation::Rotate3D(fx, fy, fz, fa),
                 &TransformOperation::Rotate3D(tx, ty, tz, ta),
             ) => {
-                let (fx, fy, fz, angle1) =
-                    transform::get_normalized_vector_and_angle(fx, fy, fz, fa);
-                let (tx, ty, tz, angle2) =
-                    transform::get_normalized_vector_and_angle(tx, ty, tz, ta);
-                if (fx, fy, fz) == (tx, ty, tz) {
-                    angle1.compute_squared_distance(&angle2)
-                } else {
-                    let v1 = DirectionVector::new(fx, fy, fz);
-                    let v2 = DirectionVector::new(tx, ty, tz);
-                    let q1 = Quaternion::from_direction_and_angle(&v1, angle1.radians64());
-                    let q2 = Quaternion::from_direction_and_angle(&v2, angle2.radians64());
-                    q1.compute_squared_distance(&q2)
-                }
+                Rotate::Rotate3D(fx, fy, fz, fa)
+                    .compute_squared_distance(&Rotate::Rotate3D(tx, ty, tz, ta))
             },
             (
                 &TransformOperation::RotateX(fa),
@@ -1390,7 +1379,7 @@ impl ComputedRotate {
         //
         // If the axis is unspecified, it defaults to "0 0 1"
         match *self {
-            Rotate::None => unreachable!("None is handled by the caller"),
+            Rotate::None => (0., 0., 1., Angle::zero()),
             Rotate::Rotate3D(rx, ry, rz, angle) => (rx, ry, rz, angle),
             Rotate::Rotate(angle) => (0., 0., 1., angle),
         }
@@ -1459,6 +1448,49 @@ impl Animate for ComputedRotate {
     }
 }
 
+impl ComputeSquaredDistance for ComputedRotate {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        match (self, other) {
+            (&Rotate::None, &Rotate::None) => Ok(SquaredDistance::from_sqrt(0.)),
+            (&Rotate::Rotate3D(_, _, _, a), &Rotate::None) |
+            (&Rotate::None, &Rotate::Rotate3D(_, _, _, a)) => {
+                a.compute_squared_distance(&Angle::zero())
+            },
+            (&Rotate::Rotate3D(_, ..), _) | (_, &Rotate::Rotate3D(_, ..)) => {
+                let (from, to) = (self.resolve(), other.resolve());
+                let (mut fx, mut fy, mut fz, angle1) =
+                    transform::get_normalized_vector_and_angle(from.0, from.1, from.2, from.3);
+                let (mut tx, mut ty, mut tz, angle2) =
+                    transform::get_normalized_vector_and_angle(to.0, to.1, to.2, to.3);
+
+                if angle1 == Angle::zero() {
+                    fx = tx;
+                    fy = ty;
+                    fz = tz;
+                } else if angle2 == Angle::zero() {
+                    tx = fx;
+                    ty = fy;
+                    tz = fz;
+                }
+
+                if (fx, fy, fz) == (tx, ty, tz) {
+                    angle1.compute_squared_distance(&angle2)
+                } else {
+                    let v1 = DirectionVector::new(fx, fy, fz);
+                    let v2 = DirectionVector::new(tx, ty, tz);
+                    let q1 = Quaternion::from_direction_and_angle(&v1, angle1.radians64());
+                    let q2 = Quaternion::from_direction_and_angle(&v2, angle2.radians64());
+                    q1.compute_squared_distance(&q2)
+                }
+            },
+            (&Rotate::Rotate(_), _) | (_, &Rotate::Rotate(_)) => {
+                self.resolve().3.compute_squared_distance(&other.resolve().3)
+            },
+        }
+    }
+}
+
 /// <https://drafts.csswg.org/css-transforms-2/#propdef-translate>
 impl ComputedTranslate {
     fn resolve(&self) -> (LengthOrPercentage, LengthOrPercentage, Length) {
@@ -1500,6 +1532,18 @@ impl Animate for ComputedTranslate {
     }
 }
 
+impl ComputeSquaredDistance for ComputedTranslate {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        let (from, to) = (self.resolve(), other.resolve());
+        Ok(
+            from.0.compute_squared_distance(&to.0)? +
+            from.1.compute_squared_distance(&to.1)? +
+            from.2.compute_squared_distance(&to.2)?
+        )
+    }
+}
+
 /// <https://drafts.csswg.org/css-transforms-2/#propdef-scale>
 impl ComputedScale {
     fn resolve(&self) -> (Number, Number, Number) {
@@ -1554,3 +1598,15 @@ impl Animate for ComputedScale {
         }
     }
 }
+
+impl ComputeSquaredDistance for ComputedScale {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        let (from, to) = (self.resolve(), other.resolve());
+        Ok(
+            from.0.compute_squared_distance(&to.0)? +
+            from.1.compute_squared_distance(&to.1)? +
+            from.2.compute_squared_distance(&to.2)?
+        )
+    }
+}

components/style/values/generics/transform.rs

@@ -530,7 +530,6 @@ pub fn get_normalized_vector_and_angle<T: Zero>(
 
 #[derive(
     Clone,
-    ComputeSquaredDistance,
     Copy,
     Debug,
     MallocSizeOf,
@@ -600,7 +599,6 @@ where
 
 #[derive(
     Clone,
-    ComputeSquaredDistance,
     Copy,
     Debug,
     MallocSizeOf,
@@ -649,7 +647,6 @@ impl<Number: ToCss + PartialEq> ToCss for Scale<Number> {
 
 #[derive(
     Clone,
-    ComputeSquaredDistance,
     Debug,
     MallocSizeOf,
     PartialEq,