Bug 1232577 part 2 - Add a hashmap to ElementCompositor to track which (pseudo-) elements need to have their animation style rule updated; r=heycam

We will eventually use this in place of the various state flags stored on
AnimationCollection (e.g. mStyleRuleRefreshTime, mStyleChanging,
mHasPendingAnimationRestyle) as well as to do a more targetted update in
FlushAnimations and AddStyleUpdatesTo.

dom/animation/EffectCompositor.cpp

@@ -29,7 +29,23 @@ using mozilla::dom::KeyframeEffectReadOnly;
 
 namespace mozilla {
 
-NS_IMPL_CYCLE_COLLECTION_0(EffectCompositor)
+NS_IMPL_CYCLE_COLLECTION_CLASS(EffectCompositor)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(EffectCompositor)
+  for (auto& elementSet : tmp->mElementsToRestyle) {
+    elementSet.Clear();
+  }
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(EffectCompositor)
+  for (auto& elementSet : tmp->mElementsToRestyle) {
+    for (auto iter = elementSet.Iter(); !iter.Done(); iter.Next()) {
+      CycleCollectionNoteChild(cb, iter.Key().mElement,
+                               "EffectCompositor::mElementsToRestyle[]",
+                               cb.Flags());
+    }
+  }
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(EffectCompositor, AddRef)
 NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(EffectCompositor, Release)

dom/animation/EffectCompositor.h

@@ -7,12 +7,15 @@
 #ifndef mozilla_EffectCompositor_h
 #define mozilla_EffectCompositor_h
 
+#include "mozilla/EnumeratedArray.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/Pair.h"
+#include "mozilla/PseudoElementHashEntry.h"
 #include "mozilla/RefPtr.h"
 #include "nsCSSProperty.h"
 #include "nsCSSPseudoElements.h"
 #include "nsCycleCollectionParticipant.h"
+#include "nsDataHashtable.h"
 #include "nsTArray.h"
 
 class nsCSSPropertySet;
@@ -129,6 +132,15 @@ private:
   static nsPresContext* GetPresContext(dom::Element* aElement);
 
   nsPresContext* mPresContext;
+
+  // Elements with a pending animation restyle. The associated bool value is
+  // true if a pending animation restyle has also been dispatched. For
+  // animations that can be throttled, we will add an entry to the hashtable to
+  // indicate that the style rule on the element is out of date but without
+  // posting a restyle to update it.
+  EnumeratedArray<CascadeLevel, CascadeLevel(kCascadeLevelCount),
+                  nsDataHashtable<PseudoElementHashEntry, bool>>
+                    mElementsToRestyle;
 };
 
 } // namespace mozilla

dom/animation/PseudoElementHashEntry.h

@@ -0,0 +1,60 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+#ifndef mozilla_PseudoElementHashEntry_h
+#define mozilla_PseudoElementHashEntry_h
+
+#include "mozilla/dom/Element.h"
+#include "mozilla/HashFunctions.h"
+#include "nsCSSPseudoElements.h"
+#include "PLDHashTable.h"
+
+namespace mozilla {
+
+struct PseudoElementHashKey
+{
+  dom::Element* mElement;
+  nsCSSPseudoElements::Type mPseudoType;
+};
+
+// A hash entry that uses a RefPtr<dom::Element>, nsCSSPseudoElements::Type pair
+class PseudoElementHashEntry : public PLDHashEntryHdr
+{
+public:
+  typedef PseudoElementHashKey KeyType;
+  typedef const PseudoElementHashKey* KeyTypePointer;
+
+  explicit PseudoElementHashEntry(KeyTypePointer aKey)
+    : mElement(aKey->mElement)
+    , mPseudoType(aKey->mPseudoType) { }
+  explicit PseudoElementHashEntry(const PseudoElementHashEntry& aCopy)=default;
+
+  ~PseudoElementHashEntry() = default;
+
+  KeyType GetKey() const { return {mElement, mPseudoType}; }
+  bool KeyEquals(KeyTypePointer aKey) const
+  {
+    return mElement == aKey->mElement &&
+           mPseudoType == aKey->mPseudoType;
+  }
+
+  static KeyTypePointer KeyToPointer(KeyType& aKey) { return &aKey; }
+  static PLDHashNumber HashKey(KeyTypePointer aKey)
+  {
+    if (!aKey)
+      return 0;
+
+    return mozilla::HashGeneric(aKey->mElement, aKey->mPseudoType);
+  }
+  enum { ALLOW_MEMMOVE = true };
+
+  RefPtr<dom::Element> mElement;
+  nsCSSPseudoElements::Type mPseudoType;
+};
+
+} // namespace mozilla
+
+#endif // mozilla_PseudoElementHashEntry_h

dom/animation/moz.build

@@ -23,6 +23,7 @@ EXPORTS.mozilla += [
     'EffectCompositor.h',
     'EffectSet.h',
     'PendingAnimationTracker.h',
+    'PseudoElementHashEntry.h',
 ]
 
 UNIFIED_SOURCES += [