From f6b587051d21ab09161f5f59a9a98dbce932ea36 Mon Sep 17 00:00:00 2001
From: Brian Birtles <birtles@gmail.com>
Date: Tue, 8 Oct 2019 01:27:29 +0000
Subject: [PATCH] style: Don't make visibility additive.

As per discussion here: https://github.com/web-platform-tests/wpt/pull/19160

This property type does not have a procedure for addition defined so it should
not be additive.

Differential Revision: https://phabricator.services.mozilla.com/D48454
---
 .../helpers/animated_properties.mako.rs       | 21 ++++++++++++-------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/components/style/properties/helpers/animated_properties.mako.rs b/components/style/properties/helpers/animated_properties.mako.rs
index 8bccd5a0bfb..c81e186a129 100644
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@@ -768,17 +768,22 @@ animated_list_impl!(<T> for crate::OwnedSlice<T>);
 animated_list_impl!(<T> for SmallVec<[T; 1]>);
 animated_list_impl!(<T> for Vec<T>);
 
-/// <https://drafts.csswg.org/css-transitions/#animtype-visibility>
+/// <https://drafts.csswg.org/web-animations-1/#animating-visibility>
 impl Animate for Visibility {
     #[inline]
     fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
-        let (this_weight, other_weight) = procedure.weights();
-        match (*self, *other) {
-            (Visibility::Visible, _) => {
-                Ok(if this_weight > 0.0 { *self } else { *other })
-            },
-            (_, Visibility::Visible) => {
-                Ok(if other_weight > 0.0 { *other } else { *self })
+        match procedure {
+            Procedure::Interpolate { .. } => {
+                let (this_weight, other_weight) = procedure.weights();
+                match (*self, *other) {
+                    (Visibility::Visible, _) => {
+                        Ok(if this_weight > 0.0 { *self } else { *other })
+                    },
+                    (_, Visibility::Visible) => {
+                        Ok(if other_weight > 0.0 { *other } else { *self })
+                    },
+                    _ => Err(()),
+                }
             },
             _ => Err(()),
         }