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/* -*- 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 */
/* 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 {
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 &&
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();
if (needDrop) {
return tmp->IsCCLeaf() || tmp->IsKnownLive();
// 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));
return tmp->IsCCLeaf() || tmp->IsKnownLive();
/* 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();
type == StyleCssRuleType::Media || type == StyleCssRuleType::Document ||
type == StyleCssRuleType::Supports ||
type == StyleCssRuleType::Keyframes || type == StyleCssRuleType::Layer);
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