Bug 1582554 - Add a preference for offset-path:ray(). r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D53110

--HG--
extra : moz-landing-system : lando

layout/style/test/mochitest.ini

@@ -8,6 +8,7 @@ prefs =
   gfx.omta.background-color=true
   layout.css.individual-transform.enabled=true
   layout.css.motion-path.enabled=true
+  layout.css.motion-path-ray.enabled=true
   layout.css.overflow-logical.enabled=true
   layout.css.step-position-jump.enabled=true
   layout.css.text-underline-offset.enabled=true

modules/libpref/init/StaticPrefList.yaml

@@ -4935,9 +4935,16 @@
 # Is support for motion-path enabled?
 - name: layout.css.motion-path.enabled
   type: bool
-  value: @IS_NOT_RELEASE_OR_BETA@
+  value: @IS_NIGHTLY_BUILD@
   mirror: always
 
+# Is support for motion-path ray() enabled?
+- name: layout.css.motion-path-ray.enabled
+  type: RelaxedAtomicBool
+  value: @IS_NIGHTLY_BUILD@
+  mirror: always
+  rust: true
+
 # Expose the media query -moz-touch-enabled to web content.
 - name: layout.css.moz-touch-enabled.enabled
   type: RelaxedAtomicBool

servo/components/style/values/specified/motion.rs

@@ -16,11 +16,24 @@ use style_traits::{ParseError, StyleParseErrorKind};
 /// The specified value of `offset-path`.
 pub type OffsetPath = GenericOffsetPath<Angle>;
 
+#[cfg(feature = "gecko")]
+fn is_ray_enabled() -> bool {
+    static_prefs::pref!("layout.css.motion-path-ray.enabled")
+}
+#[cfg(feature = "servo")]
+fn is_ray_enabled() -> bool {
+    false
+}
+
 impl Parse for RayFunction<Angle> {
     fn parse<'i, 't>(
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
+        if !is_ray_enabled() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
         let mut angle = None;
         let mut size = None;
         let mut contain = false;

testing/web-platform/meta/css/motion/__dir__.ini

@@ -1 +1 @@
-prefs: [layout.css.motion-path.enabled:true, layout.css.individual-transform.enabled:true, dom.animations-api.core.enabled:true]
+prefs: [layout.css.motion-path.enabled:true, layout.css.individual-transform.enabled:true, dom.animations-api.core.enabled:true, layout.css.motion-path-ray.enabled:true]