1 files changed, 129 insertions, 0 deletions
diff --git a/layout/style/Rule.cpp b/layout/style/Rule.cpp
new file mode 100644
index 0000000000..a107dc3f01
--- /dev/null
+++ b/layout/style/Rule.cpp
@@ -0,0 +1,129 @@
+/* -*- 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/. */
+
+/* base class for all rule types in a CSS style sheet */
+
+#include "Rule.h"
+
+#include "mozilla/css/GroupRule.h"
+#include "mozilla/dom/CSSImportRule.h"
+#include "mozilla/dom/DocumentOrShadowRoot.h"
+#include "nsCCUncollectableMarker.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/HoldDropJSObjects.h"
+#include "nsWrapperCacheInlines.h"
+#include "mozilla/ServoBindings.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+namespace mozilla::css {
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(Rule)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(Rule)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Rule)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_0(Rule)
+
+bool Rule::IsCCLeaf() const { return !PreservingWrapper(); }
+
+bool Rule::IsKnownLive() const {
+  if (HasKnownLiveWrapper()) {
+    return true;
+  }
+
+  StyleSheet* sheet = GetStyleSheet();
+  if (!sheet) {
+    return false;
+  }
+
+  Document* doc = sheet->GetKeptAliveByDocument();
+  return doc &&
+         nsCCUncollectableMarker::InGeneration(doc->GetMarkedCCGeneration());
+}
+
+void Rule::UnlinkDeclarationWrapper(nsWrapperCache& aDecl) {
+  // We have to be a bit careful here.  We have two separate nsWrapperCache
+  // instances, aDecl and this, that both correspond to the same CC participant:
+  // this.  If we just used ReleaseWrapper() on one of them, that would
+  // unpreserve that one wrapper, then trace us with a tracer that clears JS
+  // things, and we would clear the wrapper on the cache that has not
+  // unpreserved the wrapper yet.  That would violate the invariant that the
+  // cache keeps caching the wrapper until the wrapper dies.
+  //
+  // So we reimplement a modified version of nsWrapperCache::ReleaseWrapper here
+  // that unpreserves both wrappers before doing any clearing.
+  bool needDrop = PreservingWrapper() || aDecl.PreservingWrapper();
+  SetPreservingWrapper(false);
+  aDecl.SetPreservingWrapper(false);
+  if (needDrop) {
+    DropJSObjects(this);
+  }
+}
+
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_BEGIN(Rule)
+  return tmp->IsCCLeaf() || tmp->IsKnownLive();
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_END
+
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_BEGIN(Rule)
+  // Please see documentation for nsCycleCollectionParticipant::CanSkip* for why
+  // we need to check HasNothingToTrace here but not in the other two CanSkip
+  // methods.
+  return tmp->IsCCLeaf() || (tmp->IsKnownLive() && tmp->HasNothingToTrace(tmp));
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_END
+
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_BEGIN(Rule)
+  return tmp->IsCCLeaf() || tmp->IsKnownLive();
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_END
+
+/* virtual */
+void Rule::DropSheetReference() { mSheet = nullptr; }
+
+void Rule::SetCssText(const nsACString& aCssText) {
+  // We used to throw for some rule types, but not all.  Specifically, we did
+  // not throw for StyleRule.  Let's just always not throw.
+}
+
+Rule* Rule::GetParentRule() const { return mParentRule; }
+
+#ifdef DEBUG
+void Rule::AssertParentRuleType() {
+  // Would be nice to check that this->Type() is KEYFRAME_RULE when
+  // mParentRule->Tye() is KEYFRAMES_RULE, but we can't call
+  // this->Type() here since it's virtual.
+  if (mParentRule) {
+    auto type = mParentRule->Type();
+    MOZ_ASSERT(type == StyleCssRuleType::Media ||
+               type == StyleCssRuleType::Document ||
+               type == StyleCssRuleType::Supports ||
+               type == StyleCssRuleType::Keyframes ||
+               type == StyleCssRuleType::LayerBlock ||
+               type == StyleCssRuleType::Container);
+  }
+}
+#endif
+
+bool Rule::IsReadOnly() const {
+  MOZ_ASSERT(!mSheet || !mParentRule ||
+                 mSheet->IsReadOnly() == mParentRule->IsReadOnly(),
+             "a parent rule should be read only iff the owning sheet is "
+             "read only");
+  return mSheet && mSheet->IsReadOnly();
+}
+
+bool Rule::IsIncompleteImportRule() const {
+  if (Type() != StyleCssRuleType::Import) {
+    return false;
+  }
+  auto* sheet = static_cast<const dom::CSSImportRule*>(this)->GetStyleSheet();
+  return !sheet || !sheet->IsComplete();
+}
+
+}  // namespace mozilla::css