Revert "style: Make the transitions code make sense again."

This reverts commit d6092fa.

This change actually makes transitions start, and our code for stopping
transitions is just bogus, so we just keep re-starting them over and over, which
is not good.

components/style/animation.rs

@@ -345,8 +345,8 @@ impl PropertyAnimation {
 
         let property_animation = PropertyAnimation {
             property: animated_property,
-            timing_function,
-            duration,
+            timing_function: timing_function,
+            duration: duration,
         };
 
         if property_animation.does_animate() {

components/style/matching.rs

@@ -331,7 +331,7 @@ trait PrivateMatchMethods: TElement {
     fn process_animations(
         &self,
         context: &mut StyleContext<Self>,
-        old_values: Option<&Arc<ComputedValues>>,
+        old_values: &mut Option<Arc<ComputedValues>>,
         new_values: &mut Arc<ComputedValues>,
         restyle_hint: RestyleHint,
         important_rules_changed: bool,
@@ -413,7 +413,7 @@ trait PrivateMatchMethods: TElement {
     fn process_animations(
         &self,
         context: &mut StyleContext<Self>,
-        old_values: Option<&Arc<ComputedValues>>,
+        old_values: &mut Option<Arc<ComputedValues>>,
         new_values: &mut Arc<ComputedValues>,
         _restyle_hint: RestyleHint,
         _important_rules_changed: bool,
@@ -423,10 +423,11 @@ trait PrivateMatchMethods: TElement {
 
         let mut possibly_expired_animations = vec![];
         let shared_context = context.shared;
-        if old_values.is_some() {
+        if let Some(ref mut old) = *old_values {
+            // FIXME(emilio, #20116): This makes no sense.
             self.update_animations_for_cascade(
                 shared_context,
-                new_values,
+                old,
                 &mut possibly_expired_animations,
                 &context.thread_local.font_metrics_provider,
             );
@@ -445,10 +446,7 @@ trait PrivateMatchMethods: TElement {
 
         // Trigger transitions if necessary. This will reset `new_values` back
         // to its old value if it did trigger a transition.
-        //
-        // FIXME(emilio): We need logic to also stop the old transitions
-        // from running if transition-property / transition-duration changed.
-        if let Some(ref values) = old_values {
+        if let Some(ref values) = *old_values {
             animation::start_transitions_if_applicable(
                 new_animations_sender,
                 this_opaque,
@@ -575,6 +573,10 @@ trait PrivateMatchMethods: TElement {
 
     // FIXME(emilio, #20116): It's not clear to me that the name of this method
     // represents anything of what it does.
+    //
+    // Also, this function gets the old style, for some reason I don't really
+    // get, but the functions called (mainly update_style_for_animation) expects
+    // the new style, wtf?
     #[cfg(feature = "servo")]
     fn update_animations_for_cascade(
         &self,
@@ -677,7 +679,7 @@ pub trait MatchMethods: TElement {
 
         self.process_animations(
             context,
-            data.styles.primary.as_ref(),
+            &mut data.styles.primary,
             &mut new_styles.primary.style.0,
             data.hint,
             important_rules_changed,

tests/wpt/metadata/css/css-fonts/variations/font-style-interpolation.html.ini

@@ -3,4 +3,6 @@
   expected: TIMEOUT
   [font-style transition]
     expected: TIMEOUT
+  [font-style animation]
+    expected: TIMEOUT