gecko-dev/layout/style/StyleSheet.cpp

/* -*- 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/. */

#include "mozilla/StyleSheet.h"

#include "mozilla/ComputedStyleInlines.h"
#include "mozilla/css/ErrorReporter.h"
#include "mozilla/css/GroupRule.h"
#include "mozilla/dom/CSSImportRule.h"
#include "mozilla/dom/CSSRuleList.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/MediaList.h"
#include "mozilla/dom/ShadowRoot.h"
#include "mozilla/dom/ShadowRootBinding.h"
#include "mozilla/NullPrincipal.h"
#include "mozilla/ServoBindings.h"
#include "mozilla/ServoCSSRuleList.h"
#include "mozilla/ServoStyleSet.h"
#include "mozilla/StaticPrefs.h"
#include "mozilla/StyleSheetInlines.h"

#include "mozAutoDocUpdate.h"

namespace mozilla {

using namespace dom;

StyleSheet::StyleSheet(css::SheetParsingMode aParsingMode,
                       CORSMode aCORSMode,
                       net::ReferrerPolicy aReferrerPolicy,
                       const dom::SRIMetadata& aIntegrity)
  : mParent(nullptr)
  , mDocumentOrShadowRoot(nullptr)
  , mOwningNode(nullptr)
  , mOwnerRule(nullptr)
  , mParsingMode(aParsingMode)
  , mState(static_cast<State>(0))
  , mAssociationMode(NotOwnedByDocumentOrShadowRoot)
  , mInner(new StyleSheetInfo(aCORSMode, aReferrerPolicy, aIntegrity, aParsingMode))
{
  mInner->AddSheet(this);
}

StyleSheet::StyleSheet(const StyleSheet& aCopy,
                       StyleSheet* aParentToUse,
                       dom::CSSImportRule* aOwnerRuleToUse,
                       dom::DocumentOrShadowRoot* aDocumentOrShadowRoot,
                       nsINode* aOwningNodeToUse)
  : mParent(aParentToUse)
  , mTitle(aCopy.mTitle)
  , mDocumentOrShadowRoot(aDocumentOrShadowRoot)
  , mOwningNode(aOwningNodeToUse)
  , mOwnerRule(aOwnerRuleToUse)
  , mParsingMode(aCopy.mParsingMode)
  , mState(aCopy.mState)
  // We only use this constructor during cloning.  It's the cloner's
  // responsibility to notify us if we end up being owned by a document.
  , mAssociationMode(NotOwnedByDocumentOrShadowRoot)
  , mInner(aCopy.mInner) // Shallow copy, but concrete subclasses will fix up.
{
  MOZ_ASSERT(mInner, "Should only copy StyleSheets with an mInner.");
  mInner->AddSheet(this);

  if (HasForcedUniqueInner()) { // CSSOM's been there, force full copy now
    MOZ_ASSERT(IsComplete(),
               "Why have rules been accessed on an incomplete sheet?");
    // FIXME: handle failure?
    EnsureUniqueInner();
  }

  if (aCopy.mMedia) {
    // XXX This is wrong; we should be keeping @import rules and
    // sheets in sync!
    mMedia = aCopy.mMedia->Clone();
  }
}

StyleSheet::~StyleSheet()
{
  MOZ_ASSERT(!mInner, "Inner should have been dropped in LastRelease");
}

bool
StyleSheet::HasRules() const
{
  return Servo_StyleSheet_HasRules(Inner().mContents);
}

nsIDocument*
StyleSheet::GetAssociatedDocument() const
{
  return mDocumentOrShadowRoot
    ? mDocumentOrShadowRoot->AsNode().OwnerDoc()
    : nullptr;
}

nsIDocument*
StyleSheet::GetComposedDoc() const
{
  return mDocumentOrShadowRoot
    ? mDocumentOrShadowRoot->AsNode().GetComposedDoc()
    : nullptr;
}

bool
StyleSheet::IsKeptAliveByDocument() const
{
  if (mAssociationMode != OwnedByDocumentOrShadowRoot) {
    return false;
  }

  return !!GetComposedDoc();
}

void
StyleSheet::LastRelease()
{
  MOZ_ASSERT(mInner, "Should have an mInner at time of destruction.");
  MOZ_ASSERT(mInner->mSheets.Contains(this), "Our mInner should include us.");

  UnparentChildren();

  mInner->RemoveSheet(this);
  mInner = nullptr;

  DropMedia();
  DropRuleList();
}

void
StyleSheet::UnlinkInner()
{
  // We can only have a cycle through our inner if we have a unique inner,
  // because otherwise there are no JS wrappers for anything in the inner.
  if (mInner->mSheets.Length() != 1) {
    return;
  }

  // Have to be a bit careful with child sheets, because we want to
  // drop their mNext pointers and null out their mParent and
  // mDocument, but don't want to work with deleted objects.  And we
  // don't want to do any addrefing in the process, just to make sure
  // we don't confuse the cycle collector (though on the face of it,
  // addref/release pairs during unlink should probably be ok).
  RefPtr<StyleSheet> child;
  child.swap(Inner().mFirstChild);
  while (child) {
    MOZ_ASSERT(child->mParent == this, "We have a unique inner!");
    child->mParent = nullptr;
    // We (and child) might still think we're owned by a document, because
    // unlink order is non-deterministic, so the document's unlink, which would
    // tell us it does't own us anymore, may not have happened yet.  But if
    // we're being unlinked, clearly we're not owned by a document anymore
    // conceptually!
    child->ClearAssociatedDocumentOrShadowRoot();

    RefPtr<StyleSheet> next;
    // Null out child->mNext, but don't let it die yet
    next.swap(child->mNext);
    // Switch to looking at the old value of child->mNext next iteration
    child.swap(next);
    // "next" is now our previous value of child; it'll get released
    // as we loop around.
  }
}

void
StyleSheet::TraverseInner(nsCycleCollectionTraversalCallback &cb)
{
  // We can only have a cycle through our inner if we have a unique inner,
  // because otherwise there are no JS wrappers for anything in the inner.
  if (mInner->mSheets.Length() != 1) {
    return;
  }

  StyleSheet* childSheet = GetFirstChild();
  while (childSheet) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "child sheet");
    cb.NoteXPCOMChild(childSheet);
    childSheet = childSheet->mNext;
  }
}

// QueryInterface implementation for StyleSheet
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(StyleSheet)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsICSSLoaderObserver)
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(StyleSheet)
// We want to disconnect from our inner as soon as our refcount drops to zero,
// without waiting for async deletion by the cycle collector.  Otherwise we
// might end up cloning the inner if someone mutates another sheet that shares
// it with us, even though there is only one such sheet and we're about to go
// away.  This situation arises easily with sheet preloading.
NS_IMPL_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE(StyleSheet, LastRelease())

NS_IMPL_CYCLE_COLLECTION_CLASS(StyleSheet)

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(StyleSheet)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMedia)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRuleList)
  tmp->TraverseInner(cb);
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(StyleSheet)
  tmp->DropMedia();
  tmp->UnlinkInner();
  tmp->DropRuleList();
  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(StyleSheet)

mozilla::dom::CSSStyleSheetParsingMode
StyleSheet::ParsingModeDOM()
{
#define CHECK(X, Y) \
  static_assert(static_cast<int>(X) == static_cast<int>(Y),             \
                "mozilla::dom::CSSStyleSheetParsingMode and mozilla::css::SheetParsingMode should have identical values");

  CHECK(mozilla::dom::CSSStyleSheetParsingMode::Agent, css::eAgentSheetFeatures);
  CHECK(mozilla::dom::CSSStyleSheetParsingMode::User, css::eUserSheetFeatures);
  CHECK(mozilla::dom::CSSStyleSheetParsingMode::Author, css::eAuthorSheetFeatures);

#undef CHECK

  return static_cast<mozilla::dom::CSSStyleSheetParsingMode>(mParsingMode);
}

void
StyleSheet::SetComplete()
{
  MOZ_ASSERT(!HasForcedUniqueInner(),
             "Can't complete a sheet that's already been forced unique.");
  MOZ_ASSERT(!IsComplete(), "Already complete?");
  mState |= State::Complete;
  if (!Disabled()) {
    ApplicableStateChanged(true);
  }
}

void
StyleSheet::ApplicableStateChanged(bool aApplicable)
{
  if (!mDocumentOrShadowRoot) {
    return;
  }

  nsINode& node = mDocumentOrShadowRoot->AsNode();
  if (auto* shadow = ShadowRoot::FromNode(node)) {
    shadow->StyleSheetApplicableStateChanged(*this, aApplicable);
  } else {
    node.AsDocument()->SetStyleSheetApplicableState(this, aApplicable);
  }
}

void
StyleSheet::SetDisabled(bool aDisabled)
{
  if (aDisabled == Disabled()) {
    return;
  }

  if (aDisabled) {
    mState |= State::Disabled;
  } else {
    mState &= ~State::Disabled;
  }

  if (IsComplete()) {
    ApplicableStateChanged(!aDisabled);
  }
}

already_AddRefed<URLExtraData>
StyleSheet::CreateURLExtraData() const
{
  RefPtr<URLExtraData> data = new URLExtraData(GetBaseURI(),
                                               GetSheetURI(),
                                               Principal(),
                                               GetReferrerPolicy());
  return data.forget();
}
StyleSheetInfo::StyleSheetInfo(CORSMode aCORSMode,
                               ReferrerPolicy aReferrerPolicy,
                               const SRIMetadata& aIntegrity,
                               css::SheetParsingMode aParsingMode)
  : mPrincipal(NullPrincipal::CreateWithoutOriginAttributes())
  , mCORSMode(aCORSMode)
  , mReferrerPolicy(aReferrerPolicy)
  , mIntegrity(aIntegrity)
  , mContents(Servo_StyleSheet_Empty(aParsingMode).Consume())
  , mURLData(URLExtraData::Dummy())
#ifdef DEBUG
  , mPrincipalSet(false)
#endif
{
  if (!mPrincipal) {
    MOZ_CRASH("NullPrincipal::Init failed");
  }
  MOZ_COUNT_CTOR(StyleSheetInfo);
}

StyleSheetInfo::StyleSheetInfo(StyleSheetInfo& aCopy, StyleSheet* aPrimarySheet)
  : mSheetURI(aCopy.mSheetURI)
  , mOriginalSheetURI(aCopy.mOriginalSheetURI)
  , mBaseURI(aCopy.mBaseURI)
  , mPrincipal(aCopy.mPrincipal)
  , mCORSMode(aCopy.mCORSMode)
  , mReferrerPolicy(aCopy.mReferrerPolicy)
  , mIntegrity(aCopy.mIntegrity)
  , mFirstChild()  // We don't rebuild the child because we're making a copy
                   // without children.
  , mSourceMapURL(aCopy.mSourceMapURL)
  , mSourceMapURLFromComment(aCopy.mSourceMapURLFromComment)
  , mSourceURL(aCopy.mSourceURL)
  , mContents(Servo_StyleSheet_Clone(aCopy.mContents.get(), aPrimarySheet).Consume())
  , mURLData(aCopy.mURLData)
#ifdef DEBUG
  , mPrincipalSet(aCopy.mPrincipalSet)
#endif
{
  AddSheet(aPrimarySheet);

  // Our child list is fixed up by our parent.
  MOZ_COUNT_CTOR(StyleSheetInfo);
}

StyleSheetInfo::~StyleSheetInfo()
{
  MOZ_COUNT_DTOR(StyleSheetInfo);
}

StyleSheetInfo*
StyleSheetInfo::CloneFor(StyleSheet* aPrimarySheet)
{
  return new StyleSheetInfo(*this, aPrimarySheet);
}

MOZ_DEFINE_MALLOC_SIZE_OF(ServoStyleSheetMallocSizeOf)
MOZ_DEFINE_MALLOC_ENCLOSING_SIZE_OF(ServoStyleSheetMallocEnclosingSizeOf)

size_t
StyleSheetInfo::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
{
  size_t n = aMallocSizeOf(this);
  n += Servo_StyleSheet_SizeOfIncludingThis(
      ServoStyleSheetMallocSizeOf,
      ServoStyleSheetMallocEnclosingSizeOf,
      mContents);
  return n;
}

void
StyleSheetInfo::AddSheet(StyleSheet* aSheet)
{
  mSheets.AppendElement(aSheet);
}

void
StyleSheetInfo::RemoveSheet(StyleSheet* aSheet)
{
  if ((aSheet == mSheets.ElementAt(0)) && (mSheets.Length() > 1)) {
    StyleSheet::ChildSheetListBuilder::ReparentChildList(mSheets[1], mFirstChild);
  }

  if (1 == mSheets.Length()) {
    NS_ASSERTION(aSheet == mSheets.ElementAt(0), "bad parent");
    delete this;
    return;
  }

  mSheets.RemoveElement(aSheet);
}

void
StyleSheet::ChildSheetListBuilder::SetParentLinks(StyleSheet* aSheet)
{
  aSheet->mParent = parent;
  aSheet->SetAssociatedDocumentOrShadowRoot(parent->mDocumentOrShadowRoot,
                                            parent->mAssociationMode);
}

void
StyleSheet::ChildSheetListBuilder::ReparentChildList(StyleSheet* aPrimarySheet,
                                                     StyleSheet* aFirstChild)
{
  for (StyleSheet *child = aFirstChild; child; child = child->mNext) {
    child->mParent = aPrimarySheet;
    child->SetAssociatedDocumentOrShadowRoot(aPrimarySheet->mDocumentOrShadowRoot,
                                             aPrimarySheet->mAssociationMode);
  }
}

void
StyleSheet::GetType(nsAString& aType)
{
  aType.AssignLiteral("text/css");
}

void
StyleSheet::GetHref(nsAString& aHref, ErrorResult& aRv)
{
  if (nsIURI* sheetURI = Inner().mOriginalSheetURI) {
    nsAutoCString str;
    nsresult rv = sheetURI->GetSpec(str);
    if (NS_FAILED(rv)) {
      aRv.Throw(rv);
      return;
    }
    CopyUTF8toUTF16(str, aHref);
  } else {
    SetDOMStringToNull(aHref);
  }
}

void
StyleSheet::GetTitle(nsAString& aTitle)
{
  // From https://drafts.csswg.org/cssom/#dom-stylesheet-title:
  //
  //    The title attribute must return the title or null if title is the empty
  //    string.
  //
  if (!mTitle.IsEmpty()) {
    aTitle.Assign(mTitle);
  } else {
    SetDOMStringToNull(aTitle);
  }
}

void
StyleSheet::WillDirty()
{
  if (IsComplete()) {
    EnsureUniqueInner();
  }
}

void
StyleSheet::AddStyleSet(ServoStyleSet* aStyleSet)
{
  NS_ASSERTION(!mStyleSets.Contains(aStyleSet),
               "style set already registered");
  mStyleSets.AppendElement(aStyleSet);
}

void
StyleSheet::DropStyleSet(ServoStyleSet* aStyleSet)
{
  DebugOnly<bool> found = mStyleSets.RemoveElement(aStyleSet);
  NS_ASSERTION(found, "didn't find style set");
}

void
StyleSheet::EnsureUniqueInner()
{
  MOZ_ASSERT(mInner->mSheets.Length() != 0,
             "unexpected number of outers");
  mState |= State::ForcedUniqueInner;

  if (HasUniqueInner()) {
    // already unique
    return;
  }

  StyleSheetInfo* clone = mInner->CloneFor(this);
  MOZ_ASSERT(clone);
  mInner->RemoveSheet(this);
  mInner = clone;

  // Fixup the child lists and parent links in the Servo sheet. This is done
  // here instead of in StyleSheetInner::CloneFor, because it's just more
  // convenient to do so instead.
  BuildChildListAfterInnerClone();

  // let our containing style sets know that if we call
  // nsPresContext::EnsureSafeToHandOutCSSRules we will need to restyle the
  // document
  for (ServoStyleSet* setHandle : mStyleSets) {
    setHandle->SetNeedsRestyleAfterEnsureUniqueInner();
  }
}

void
StyleSheet::AppendAllChildSheets(nsTArray<StyleSheet*>& aArray)
{
  for (StyleSheet* child = GetFirstChild(); child; child = child->mNext) {
    aArray.AppendElement(child);
  }
}

// WebIDL CSSStyleSheet API

dom::CSSRuleList*
StyleSheet::GetCssRules(nsIPrincipal& aSubjectPrincipal, ErrorResult& aRv)
{
  if (!AreRulesAvailable(aSubjectPrincipal, aRv)) {
    return nullptr;
  }
  return GetCssRulesInternal();
}

void
StyleSheet::GetSourceMapURL(nsAString& aSourceMapURL)
{
  if (mInner->mSourceMapURL.IsEmpty()) {
    aSourceMapURL = mInner->mSourceMapURLFromComment;
  } else {
    aSourceMapURL = mInner->mSourceMapURL;
  }
}

void
StyleSheet::SetSourceMapURL(const nsAString& aSourceMapURL)
{
  mInner->mSourceMapURL = aSourceMapURL;
}

void
StyleSheet::SetSourceMapURLFromComment(const nsAString& aSourceMapURLFromComment)
{
  mInner->mSourceMapURLFromComment = aSourceMapURLFromComment;
}

void
StyleSheet::GetSourceURL(nsAString& aSourceURL)
{
  aSourceURL = mInner->mSourceURL;
}

void
StyleSheet::SetSourceURL(const nsAString& aSourceURL)
{
  mInner->mSourceURL = aSourceURL;
}

css::Rule*
StyleSheet::GetDOMOwnerRule() const
{
  return mOwnerRule;
}

uint32_t
StyleSheet::InsertRule(const nsAString& aRule, uint32_t aIndex,
                       nsIPrincipal& aSubjectPrincipal,
                       ErrorResult& aRv)
{
  if (!AreRulesAvailable(aSubjectPrincipal, aRv)) {
    return 0;
  }
  return InsertRuleInternal(aRule, aIndex, aRv);
}

void
StyleSheet::DeleteRule(uint32_t aIndex,
                       nsIPrincipal& aSubjectPrincipal,
                       ErrorResult& aRv)
{
  if (!AreRulesAvailable(aSubjectPrincipal, aRv)) {
    return;
  }
  return DeleteRuleInternal(aIndex, aRv);
}

nsresult
StyleSheet::DeleteRuleFromGroup(css::GroupRule* aGroup, uint32_t aIndex)
{
  NS_ENSURE_ARG_POINTER(aGroup);
  NS_ASSERTION(IsComplete(), "No deleting from an incomplete sheet!");
  RefPtr<css::Rule> rule = aGroup->GetStyleRuleAt(aIndex);
  NS_ENSURE_TRUE(rule, NS_ERROR_ILLEGAL_VALUE);

  // check that the rule actually belongs to this sheet!
  if (this != rule->GetStyleSheet()) {
    return NS_ERROR_INVALID_ARG;
  }

  WillDirty();

  nsresult result = aGroup->DeleteStyleRuleAt(aIndex);
  NS_ENSURE_SUCCESS(result, result);

  rule->DropReferences();

  RuleRemoved(*rule);
  return NS_OK;
}

dom::ShadowRoot*
StyleSheet::GetContainingShadow() const
{
  if (!mOwningNode || !mOwningNode->IsContent()) {
    return nullptr;
  }

  return mOwningNode->AsContent()->GetContainingShadow();
}

#define NOTIFY(function_, args_) do {                     \
  StyleSheet* current = this;                             \
  do {                                                    \
    for (ServoStyleSet* handle : current->mStyleSets) {   \
      handle->function_ args_;                            \
    }                                                     \
    if (auto* shadow = current->GetContainingShadow()) {  \
      shadow->function_ args_;                            \
    }                                                     \
    current = current->mParent;                           \
  } while (current);                                      \
} while (0)

void
StyleSheet::RuleAdded(css::Rule& aRule)
{
  mState |= State::ModifiedRules;
  NOTIFY(RuleAdded, (*this, aRule));

  if (nsIDocument* doc = GetComposedDoc()) {
    doc->StyleRuleAdded(this, &aRule);
  }
}

void
StyleSheet::RuleRemoved(css::Rule& aRule)
{
  mState |= State::ModifiedRules;
  NOTIFY(RuleRemoved, (*this, aRule));

  if (nsIDocument* doc = GetComposedDoc()) {
    doc->StyleRuleRemoved(this, &aRule);
  }
}

void
StyleSheet::RuleChanged(css::Rule* aRule)
{
  mState |= State::ModifiedRules;
  NOTIFY(RuleChanged, (*this, aRule));

  if (nsIDocument* doc = GetComposedDoc()) {
    doc->StyleRuleChanged(this, aRule);
  }
}

#undef NOTIFY

nsresult
StyleSheet::InsertRuleIntoGroup(const nsAString& aRule,
                                css::GroupRule* aGroup,
                                uint32_t aIndex)
{
  NS_ASSERTION(IsComplete(), "No inserting into an incomplete sheet!");
  // check that the group actually belongs to this sheet!
  if (this != aGroup->GetStyleSheet()) {
    return NS_ERROR_INVALID_ARG;
  }

  WillDirty();

  nsresult result = InsertRuleIntoGroupInternal(aRule, aGroup, aIndex);
  NS_ENSURE_SUCCESS(result, result);
  RuleAdded(*aGroup->GetStyleRuleAt(aIndex));
  return NS_OK;
}

uint64_t
StyleSheet::FindOwningWindowInnerID() const
{
  uint64_t windowID = 0;
  if (nsIDocument* doc = GetAssociatedDocument()) {
    windowID = doc->InnerWindowID();
  }

  if (windowID == 0 && mOwningNode) {
    windowID = mOwningNode->OwnerDoc()->InnerWindowID();
  }

  RefPtr<css::Rule> ownerRule;
  if (windowID == 0 && (ownerRule = GetDOMOwnerRule())) {
    RefPtr<StyleSheet> sheet = ownerRule->GetStyleSheet();
    if (sheet) {
      windowID = sheet->FindOwningWindowInnerID();
    }
  }

  if (windowID == 0 && mParent) {
    windowID = mParent->FindOwningWindowInnerID();
  }

  return windowID;
}

void
StyleSheet::UnparentChildren()
{
  // XXXbz this is a little bogus; see the XXX comment where we
  // declare mFirstChild in StyleSheetInfo.
  for (StyleSheet* child = GetFirstChild();
       child;
       child = child->mNext) {
    if (child->mParent == this) {
      child->mParent = nullptr;
      MOZ_ASSERT(child->mAssociationMode == NotOwnedByDocumentOrShadowRoot,
                 "How did we get to the destructor, exactly, if we're owned "
                 "by a document?");
      child->mDocumentOrShadowRoot = nullptr;
    }
  }
}

void
StyleSheet::SubjectSubsumesInnerPrincipal(nsIPrincipal& aSubjectPrincipal,
                                          ErrorResult& aRv)
{
  StyleSheetInfo& info = Inner();

  if (aSubjectPrincipal.Subsumes(info.mPrincipal)) {
    return;
  }

  // Allow access only if CORS mode is not NONE and the security flag
  // is not turned off.
  if (GetCORSMode() == CORS_NONE &&
      !nsContentUtils::BypassCSSOMOriginCheck()) {
    aRv.Throw(NS_ERROR_DOM_SECURITY_ERR);
    return;
  }

  // Now make sure we set the principal of our inner to the subjectPrincipal.
  // We do this because we're in a situation where the caller would not normally
  // be able to access the sheet, but the sheet has opted in to being read.
  // Unfortunately, that means it's also opted in to being _edited_, and if the
  // caller now makes edits to the sheet we want the resulting resource loads,
  // if any, to look as if they are coming from the caller's principal, not the
  // original sheet principal.
  //
  // That means we need a unique inner, of course.  But we don't want to do that
  // if we're not complete yet.  Luckily, all the callers of this method throw
  // anyway if not complete, so we can just do that here too.
  if (!IsComplete()) {
    aRv.Throw(NS_ERROR_DOM_INVALID_ACCESS_ERR);
    return;
  }

  WillDirty();

  info.mPrincipal = &aSubjectPrincipal;
}

bool
StyleSheet::AreRulesAvailable(nsIPrincipal& aSubjectPrincipal,
                              ErrorResult& aRv)
{
  // Rules are not available on incomplete sheets.
  if (!IsComplete()) {
    aRv.Throw(NS_ERROR_DOM_INVALID_ACCESS_ERR);
    return false;
  }
  //-- Security check: Only scripts whose principal subsumes that of the
  //   style sheet can access rule collections.
  SubjectSubsumesInnerPrincipal(aSubjectPrincipal, aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return false;
  }
  return true;
}

StyleSheet*
StyleSheet::GetFirstChild() const
{
  return Inner().mFirstChild;
}

void
StyleSheet::SetAssociatedDocumentOrShadowRoot(DocumentOrShadowRoot* aDocOrShadowRoot,
                                              AssociationMode aAssociationMode)
{
  MOZ_ASSERT(aDocOrShadowRoot ||
             aAssociationMode == NotOwnedByDocumentOrShadowRoot);

  // not ref counted
  mDocumentOrShadowRoot = aDocOrShadowRoot;
  mAssociationMode = aAssociationMode;

  // Now set the same document on all our child sheets....
  // XXXbz this is a little bogus; see the XXX comment where we
  // declare mFirstChild.
  for (StyleSheet* child = GetFirstChild();
       child; child = child->mNext) {
    if (child->mParent == this) {
      child->SetAssociatedDocumentOrShadowRoot(aDocOrShadowRoot, aAssociationMode);
    }
  }
}

void
StyleSheet::PrependStyleSheet(StyleSheet* aSheet)
{
  WillDirty();
  PrependStyleSheetSilently(aSheet);
}

void
StyleSheet::PrependStyleSheetSilently(StyleSheet* aSheet)
{
  MOZ_ASSERT(aSheet);

  aSheet->mNext = Inner().mFirstChild;
  Inner().mFirstChild = aSheet;

  // This is not reference counted. Our parent tells us when
  // it's going away.
  aSheet->mParent = this;
  aSheet->SetAssociatedDocumentOrShadowRoot(mDocumentOrShadowRoot, mAssociationMode);
}

size_t
StyleSheet::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
{
  size_t n = 0;
  const StyleSheet* s = this;
  while (s) {
    n += aMallocSizeOf(s);

    // See the comment in CSSStyleSheet::SizeOfIncludingThis() for an
    // explanation of this.
    //
    // FIXME(emilio): This comment is gone, someone should go find it.
    if (s->Inner().mSheets.LastElement() == s) {
      n += s->Inner().SizeOfIncludingThis(aMallocSizeOf);
    }

    // Measurement of the following members may be added later if DMD finds it
    // is worthwhile:
    // - s->mTitle
    // - s->mMedia
    // - s->mStyleSets
    // - s->mRuleList

    s = s->mNext;
  }
  return n;
}

#ifdef DEBUG
void
StyleSheet::List(FILE* out, int32_t aIndent) const
{
  int32_t index;

  // Indent
  nsAutoCString str;
  for (index = aIndent; --index >= 0; ) {
    str.AppendLiteral("  ");
  }

  str.AppendLiteral("CSS Style Sheet: ");
  nsAutoCString urlSpec;
  nsresult rv = GetSheetURI()->GetSpec(urlSpec);
  if (NS_SUCCEEDED(rv) && !urlSpec.IsEmpty()) {
    str.Append(urlSpec);
  }

  if (mMedia) {
    str.AppendLiteral(" media: ");
    nsAutoString  buffer;
    mMedia->GetText(buffer);
    AppendUTF16toUTF8(buffer, str);
  }
  str.Append('\n');
  fprintf_stderr(out, "%s", str.get());

  for (const StyleSheet* child = GetFirstChild();
       child;
       child = child->mNext) {
    child->List(out, aIndent + 1);
  }
}
#endif

void
StyleSheet::SetMedia(dom::MediaList* aMedia)
{
  if (aMedia) {
    aMedia->SetStyleSheet(this);
  }
  mMedia = aMedia;
}

void
StyleSheet::SetReferrerPolicy(net::ReferrerPolicy aReferrerPolicy)
{
  Inner().mReferrerPolicy = aReferrerPolicy;
}

void
StyleSheet::DropMedia()
{
  if (mMedia) {
    mMedia->SetStyleSheet(nullptr);
    mMedia = nullptr;
  }
}

dom::MediaList*
StyleSheet::Media()
{
  if (!mMedia) {
    mMedia = dom::MediaList::Create(nsString());
    mMedia->SetStyleSheet(this);
  }

  return mMedia;
}

// nsWrapperCache

JSObject*
StyleSheet::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
{
  return dom::CSSStyleSheet_Binding::Wrap(aCx, this, aGivenProto);
}

/* static */ bool
StyleSheet::RuleHasPendingChildSheet(css::Rule* aRule)
{
  MOZ_ASSERT(aRule->Type() == dom::CSSRule_Binding::IMPORT_RULE);
  auto rule = static_cast<dom::CSSImportRule*>(aRule);
  if (StyleSheet* childSheet = rule->GetStyleSheet()) {
    return !childSheet->IsComplete();
  }
  return false;
}

void
StyleSheet::BuildChildListAfterInnerClone()
{
  MOZ_ASSERT(Inner().mSheets.Length() == 1, "Should've just cloned");
  MOZ_ASSERT(Inner().mSheets[0] == this);
  MOZ_ASSERT(!Inner().mFirstChild);

  auto* contents = Inner().mContents.get();
  RefPtr<ServoCssRules> rules =
    Servo_StyleSheet_GetRules(contents).Consume();

  uint32_t index = 0;
  while (true) {
    uint32_t line, column; // Actually unused.
    RefPtr<RawServoImportRule> import =
      Servo_CssRules_GetImportRuleAt(rules, index, &line, &column).Consume();
    if (!import) {
      // Note that only @charset rules come before @import rules, and @charset
      // rules are parsed but skipped, so we can stop iterating as soon as we
      // find something that isn't an @import rule.
      break;
    }
    auto* sheet =
      const_cast<StyleSheet*>(Servo_ImportRule_GetSheet(import));
    MOZ_ASSERT(sheet);
    PrependStyleSheetSilently(sheet);
    index++;
  }
}

already_AddRefed<StyleSheet>
StyleSheet::CreateEmptyChildSheet(
    already_AddRefed<dom::MediaList> aMediaList) const
{
  RefPtr<StyleSheet> child =
    new StyleSheet(ParsingMode(),
                   CORSMode::CORS_NONE,
                   GetReferrerPolicy(),
                   SRIMetadata());

  child->mMedia = aMediaList;
  return child.forget();
}

// We disable parallel stylesheet parsing if any of the following three
// conditions hold:
//
// (1) The pref is off.
// (2) The browser is recording CSS errors (which parallel parsing can't
//     handle).
// (3) The stylesheet is a chrome stylesheet, since those can use
//     -moz-bool-pref, which needs to access the pref service, which is
//     not threadsafe.
static bool
AllowParallelParse(css::Loader* aLoader, nsIURI* aSheetURI)
{
  // Check the pref.
  if (!StaticPrefs::layout_css_parsing_parallel()) {
    return false;
  }

  // If the browser is recording CSS errors, we need to use the sequential path
  // because the parallel path doesn't support that.
  nsIDocument* doc = aLoader->GetDocument();
  if (doc && css::ErrorReporter::ShouldReportErrors(*doc)) {
    return false;
  }

  // If this is a chrome stylesheet, it might use -moz-bool-pref, which needs to
  // access the pref service, which is not thread-safe. We could probably expose
  // the relevant booleans as thread-safe var caches if we needed to, but
  // parsing chrome stylesheets in parallel is unlikely to be a win anyway.
  //
  // Note that UA stylesheets can also use -moz-bool-pref, but those are always
  // parsed sync.
  if (dom::IsChromeURI(aSheetURI)) {
    return false;
  }

  return true;
}

RefPtr<StyleSheetParsePromise>
StyleSheet::ParseSheet(css::Loader* aLoader,
                       const nsACString& aBytes,
                       css::SheetLoadData* aLoadData)
{
  MOZ_ASSERT(aLoader);
  MOZ_ASSERT(aLoadData);
  MOZ_ASSERT(mParsePromise.IsEmpty());
  RefPtr<StyleSheetParsePromise> p = mParsePromise.Ensure(__func__);
  Inner().mURLData = CreateURLExtraData(); // RefPtr

  const StyleUseCounters* useCounters = aLoader->GetDocument()
    ? aLoader->GetDocument()->GetStyleUseCounters()
    : nullptr;

  if (!AllowParallelParse(aLoader, GetSheetURI())) {
    RefPtr<RawServoStyleSheetContents> contents =
      Servo_StyleSheet_FromUTF8Bytes(aLoader,
                                     this,
                                     aLoadData,
                                     &aBytes,
                                     mParsingMode,
                                     Inner().mURLData,
                                     aLoadData->mLineNumber,
                                     aLoader->GetCompatibilityMode(),
                                     /* reusable_sheets = */ nullptr,
                                     useCounters)
      .Consume();
    FinishAsyncParse(contents.forget());
  } else {
    RefPtr<css::SheetLoadDataHolder> loadDataHolder =
      new css::SheetLoadDataHolder(__func__, aLoadData);
    Servo_StyleSheet_FromUTF8BytesAsync(loadDataHolder,
                                        Inner().mURLData,
                                        &aBytes,
                                        mParsingMode,
                                        aLoadData->mLineNumber,
                                        aLoader->GetCompatibilityMode(),
                                        /* should_record_counters = */ !!useCounters);
  }

  return p;
}

void
StyleSheet::FinishAsyncParse(already_AddRefed<RawServoStyleSheetContents> aSheetContents)
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(!mParsePromise.IsEmpty());
  Inner().mContents = aSheetContents;
  FinishParse();
  mParsePromise.Resolve(true, __func__);
}


void
StyleSheet::ParseSheetSync(css::Loader* aLoader,
                           const nsACString& aBytes,
                           css::SheetLoadData* aLoadData,
                           uint32_t aLineNumber,
                           css::LoaderReusableStyleSheets* aReusableSheets)
{
  nsCompatibility compatMode =
    aLoader ? aLoader->GetCompatibilityMode() : eCompatibility_FullStandards;

  const StyleUseCounters* useCounters = aLoader && aLoader->GetDocument()
    ? aLoader->GetDocument()->GetStyleUseCounters()
    : nullptr;

  Inner().mURLData = CreateURLExtraData(); // RefPtr
  Inner().mContents = Servo_StyleSheet_FromUTF8Bytes(aLoader,
                                                     this,
                                                     aLoadData,
                                                     &aBytes,
                                                     mParsingMode,
                                                     Inner().mURLData,
                                                     aLineNumber,
                                                     compatMode,
                                                     aReusableSheets,
                                                     useCounters)
                         .Consume();

  FinishParse();
}

void
StyleSheet::FinishParse()
{
  nsString sourceMapURL;
  Servo_StyleSheet_GetSourceMapURL(Inner().mContents, &sourceMapURL);
  SetSourceMapURLFromComment(sourceMapURL);

  nsString sourceURL;
  Servo_StyleSheet_GetSourceURL(Inner().mContents, &sourceURL);
  SetSourceURL(sourceURL);
}

nsresult
StyleSheet::ReparseSheet(const nsAString& aInput)
{
  if (!IsComplete()) {
    return NS_ERROR_DOM_INVALID_ACCESS_ERR;
  }

  // Hold strong ref to the CSSLoader in case the document update
  // kills the document
  RefPtr<css::Loader> loader;
  if (nsIDocument* doc = GetAssociatedDocument()) {
    loader = doc->CSSLoader();
    NS_ASSERTION(loader, "Document with no CSS loader!");
  } else {
    loader = new css::Loader;
  }

  WillDirty();

  // cache child sheets to reuse
  css::LoaderReusableStyleSheets reusableSheets;
  for (StyleSheet* child = GetFirstChild(); child; child = child->mNext) {
    if (child->GetOriginalURI()) {
      reusableSheets.AddReusableSheet(child);
    }
  }

  // clean up child sheets list
  for (StyleSheet* child = GetFirstChild(); child; ) {
    StyleSheet* next = child->mNext;
    child->mParent = nullptr;
    child->ClearAssociatedDocumentOrShadowRoot();
    child->mNext = nullptr;
    child = next;
  }
  Inner().mFirstChild = nullptr;

  uint32_t lineNumber = 1;
  if (mOwningNode) {
    nsCOMPtr<nsIStyleSheetLinkingElement> link = do_QueryInterface(mOwningNode);
    if (link) {
      lineNumber = link->GetLineNumber();
    }
  }

  // Notify to the stylesets about the old rules going away.
  {
    ServoCSSRuleList* ruleList = GetCssRulesInternal();
    MOZ_ASSERT(ruleList);

    uint32_t ruleCount = ruleList->Length();
    for (uint32_t i = 0; i < ruleCount; ++i) {
      css::Rule* rule = ruleList->GetRule(i);
      MOZ_ASSERT(rule);
      if (rule->Type() == dom::CSSRule_Binding::IMPORT_RULE &&
          RuleHasPendingChildSheet(rule)) {
        continue; // notify when loaded (see StyleSheetLoaded)
      }
      RuleRemoved(*rule);
    }
  }

  DropRuleList();

  ParseSheetSync(loader,
                 NS_ConvertUTF16toUTF8(aInput),
                 /* aLoadData = */ nullptr,
                 lineNumber,
                 &reusableSheets);

  // Notify the stylesets about the new rules.
  {
    // Get the rule list (which will need to be regenerated after ParseSheet).
    ServoCSSRuleList* ruleList = GetCssRulesInternal();
    MOZ_ASSERT(ruleList);

    uint32_t ruleCount = ruleList->Length();
    for (uint32_t i = 0; i < ruleCount; ++i) {
      css::Rule* rule = ruleList->GetRule(i);
      MOZ_ASSERT(rule);
      if (rule->Type() == CSSRule_Binding::IMPORT_RULE &&
          RuleHasPendingChildSheet(rule)) {
        continue; // notify when loaded (see StyleSheetLoaded)
      }

      RuleAdded(*rule);
    }
  }

  // Our rules are no longer considered modified.
  ClearModifiedRules();

  return NS_OK;
}

// nsICSSLoaderObserver implementation
NS_IMETHODIMP
StyleSheet::StyleSheetLoaded(StyleSheet* aSheet,
                             bool aWasAlternate,
                             nsresult aStatus)
{
  if (!aSheet->GetParentSheet()) {
    return NS_OK; // ignore if sheet has been detached already
  }
  NS_ASSERTION(this == aSheet->GetParentSheet(),
               "We are being notified of a sheet load for a sheet that is not our child!");

  if (NS_SUCCEEDED(aStatus)) {
    RuleAdded(*aSheet->GetOwnerRule());
  }

  return NS_OK;
}

void
StyleSheet::DropRuleList()
{
  if (mRuleList) {
    mRuleList->DropReferences();
    mRuleList = nullptr;
  }
}

already_AddRefed<StyleSheet>
StyleSheet::Clone(StyleSheet* aCloneParent,
                  dom::CSSImportRule* aCloneOwnerRule,
                  dom::DocumentOrShadowRoot* aCloneDocumentOrShadowRoot,
                  nsINode* aCloneOwningNode) const
{
  RefPtr<StyleSheet> clone =
    new StyleSheet(*this,
                   aCloneParent,
                   aCloneOwnerRule,
                   aCloneDocumentOrShadowRoot,
                   aCloneOwningNode);
  return clone.forget();
}

ServoCSSRuleList*
StyleSheet::GetCssRulesInternal()
{
  if (!mRuleList) {
    EnsureUniqueInner();

    RefPtr<ServoCssRules> rawRules =
      Servo_StyleSheet_GetRules(Inner().mContents).Consume();
    MOZ_ASSERT(rawRules);
    mRuleList = new ServoCSSRuleList(rawRules.forget(), this, nullptr);
  }
  return mRuleList;
}

uint32_t
StyleSheet::InsertRuleInternal(const nsAString& aRule,
                               uint32_t aIndex,
                               ErrorResult& aRv)
{
  // Ensure mRuleList is constructed.
  GetCssRulesInternal();

  aRv = mRuleList->InsertRule(aRule, aIndex);
  if (aRv.Failed()) {
    return 0;
  }

  // XXX We may not want to get the rule when stylesheet change event
  // is not enabled.
  css::Rule* rule = mRuleList->GetRule(aIndex);
  if (rule->Type() != CSSRule_Binding::IMPORT_RULE ||
      !RuleHasPendingChildSheet(rule)) {
    RuleAdded(*rule);
  }

  return aIndex;
}

void
StyleSheet::DeleteRuleInternal(uint32_t aIndex, ErrorResult& aRv)
{
  // Ensure mRuleList is constructed.
  GetCssRulesInternal();
  if (aIndex >= mRuleList->Length()) {
    aRv.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
    return;
  }

  // Hold a strong ref to the rule so it doesn't die when we remove it
  // from the list. XXX We may not want to hold it if stylesheet change
  // event is not enabled.
  RefPtr<css::Rule> rule = mRuleList->GetRule(aIndex);
  aRv = mRuleList->DeleteRule(aIndex);
  MOZ_ASSERT(!aRv.ErrorCodeIs(NS_ERROR_DOM_INDEX_SIZE_ERR),
             "IndexSizeError should have been handled earlier");
  if (!aRv.Failed()) {
    RuleRemoved(*rule);
  }
}

nsresult
StyleSheet::InsertRuleIntoGroupInternal(const nsAString& aRule,
                                             css::GroupRule* aGroup,
                                             uint32_t aIndex)
{
  auto rules = static_cast<ServoCSSRuleList*>(aGroup->CssRules());
  MOZ_ASSERT(rules->GetParentRule() == aGroup);
  return rules->InsertRule(aRule, aIndex);
}

OriginFlags
StyleSheet::GetOrigin()
{
  return static_cast<OriginFlags>(
    Servo_StyleSheet_GetOrigin(Inner().mContents));
}

} // namespace mozilla