From 8101887d31c69d47e30bb31c09bde0560aace5e8 Mon Sep 17 00:00:00 2001
From: Anthony Ramine <n.oxyde@gmail.com>
Date: Sat, 26 Aug 2017 00:07:02 +0200
Subject: [PATCH] Support #[animation(constant)] when deriving ToAnimatedZero

---
 components/style/values/animated/effects.rs | 11 ----------
 components/style/values/computed/length.rs  | 17 +++------------
 components/style/values/generics/effects.rs |  3 ++-
 components/style_derive/to_animated_zero.rs | 23 ++++++++++++++++-----
 4 files changed, 23 insertions(+), 31 deletions(-)

diff --git a/components/style/values/animated/effects.rs b/components/style/values/animated/effects.rs
index 3fd595cebeb..eb03bd9565b 100644
--- a/components/style/values/animated/effects.rs
+++ b/components/style/values/animated/effects.rs
@@ -152,17 +152,6 @@ impl ComputeSquaredDistance for BoxShadow {
     }
 }
 
-impl ToAnimatedZero for BoxShadow {
-    #[inline]
-    fn to_animated_zero(&self) -> Result<Self, ()> {
-        Ok(BoxShadow {
-            base: self.base.to_animated_zero()?,
-            spread: self.spread.to_animated_zero()?,
-            inset: self.inset,
-        })
-    }
-}
-
 impl ToAnimatedValue for ComputedFilterList {
     type AnimatedValue = FilterList;
 
diff --git a/components/style/values/computed/length.rs b/components/style/values/computed/length.rs
index 3da3ea9c9a5..a6600a806a2 100644
--- a/components/style/values/computed/length.rs
+++ b/components/style/values/computed/length.rs
@@ -11,7 +11,6 @@ use style_traits::ToCss;
 use style_traits::values::specified::AllowedLengthType;
 use super::{Number, ToComputedValue, Context, Percentage};
 use values::{Auto, CSSFloat, Either, ExtremumLength, None_, Normal, specified};
-use values::animated::ToAnimatedZero;
 use values::computed::{NonNegativeAu, NonNegativeNumber};
 use values::distance::{ComputeSquaredDistance, SquaredDistance};
 use values::generics::NonNegative;
@@ -64,26 +63,16 @@ impl ToComputedValue for specified::Length {
     }
 }
 
-#[derive(Clone, Copy, Debug, PartialEq)]
-#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[derive(Clone, Copy, Debug, PartialEq, ToAnimatedZero)]
 pub struct CalcLengthOrPercentage {
+    #[animation(constant)]
     pub clamping_mode: AllowedLengthType,
     length: Au,
     pub percentage: Option<Percentage>,
 }
 
-impl ToAnimatedZero for CalcLengthOrPercentage {
-    #[inline]
-    fn to_animated_zero(&self) -> Result<Self, ()> {
-        Ok(CalcLengthOrPercentage {
-            clamping_mode: self.clamping_mode,
-            length: self.length.to_animated_zero()?,
-            percentage: self.percentage.to_animated_zero()?,
-        })
-    }
-}
-
 impl ComputeSquaredDistance for CalcLengthOrPercentage {
     #[inline]
     fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
diff --git a/components/style/values/generics/effects.rs b/components/style/values/generics/effects.rs
index 572a211544f..5d95ae19a8f 100644
--- a/components/style/values/generics/effects.rs
+++ b/components/style/values/generics/effects.rs
@@ -11,7 +11,8 @@ use values::specified::url::SpecifiedUrl;
 
 /// A generic value for a single `box-shadow`.
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-#[derive(Animate, Clone, Debug, HasViewportPercentage, PartialEq, ToAnimatedValue)]
+#[derive(Animate, Clone, Debug, HasViewportPercentage, PartialEq)]
+#[derive(ToAnimatedValue, ToAnimatedZero)]
 pub struct BoxShadow<Color, SizeLength, BlurShapeLength, ShapeLength> {
     /// The base shadow.
     pub base: SimpleShadow<Color, SizeLength, BlurShapeLength>,
diff --git a/components/style_derive/to_animated_zero.rs b/components/style_derive/to_animated_zero.rs
index 50f905ccdc1..2c76935c6dd 100644
--- a/components/style_derive/to_animated_zero.rs
+++ b/components/style_derive/to_animated_zero.rs
@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use animate::AnimateAttrs;
+use animate::{AnimateAttrs, AnimateFieldAttrs};
 use cg;
 use quote;
 use syn;
@@ -25,10 +25,23 @@ pub fn derive(input: syn::DeriveInput) -> quote::Tokens {
         let bindings_pairs = bindings.into_iter().zip(mapped_bindings);
         let mut computations = quote!();
         computations.append_all(bindings_pairs.map(|(binding, mapped_binding)| {
-            where_clause.add_trait_bound(binding.field.ty.clone());
-            quote! {
-                let #mapped_binding =
-                    ::values::animated::ToAnimatedZero::to_animated_zero(#binding)?;
+            let field_attrs = cg::parse_field_attrs::<AnimateFieldAttrs>(&binding.field);
+            if field_attrs.constant {
+                if cg::is_parameterized(&binding.field.ty, where_clause.params) {
+                    where_clause.inner.predicates.push(cg::where_predicate(
+                        binding.field.ty.clone(),
+                        &["std", "clone", "Clone"],
+                    ));
+                }
+                quote! {
+                    let #mapped_binding = ::std::clone::Clone::clone(#binding);
+                }
+            } else {
+                where_clause.add_trait_bound(binding.field.ty.clone());
+                quote! {
+                    let #mapped_binding =
+                        ::values::animated::ToAnimatedZero::to_animated_zero(#binding)?;
+                }
             }
         }));
         computations.append(quote! { Ok(#mapped) });