layout/style/Rule.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* base class for all rule types in a CSS style sheet */
   8
   9 #include "Rule.h"
  10
  11 #include "mozilla/css/GroupRule.h"
  12 #include "mozilla/dom/CSSImportRule.h"
  13 #include "mozilla/dom/DocumentOrShadowRoot.h"
  14 #include "nsCCUncollectableMarker.h"
  15 #include "mozilla/dom/Document.h"
  16 #include "mozilla/HoldDropJSObjects.h"
  17 #include "nsWrapperCacheInlines.h"
  18 #include "mozilla/ServoBindings.h"
  19
  20 using namespace mozilla;
  21 using namespace mozilla::dom;
  22
  23 namespace mozilla::css {
  24
  25 NS_IMPL_CYCLE_COLLECTING_ADDREF(Rule)
  26 NS_IMPL_CYCLE_COLLECTING_RELEASE(Rule)
  27
  28 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Rule)
  29   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  30   NS_INTERFACE_MAP_ENTRY(nsISupports)
  31 NS_INTERFACE_MAP_END
  32
  33 NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_0(Rule)
  34
  35 bool Rule::IsCCLeaf() const { return !PreservingWrapper(); }
  36
  37 bool Rule::IsKnownLive() const {
  38   if (HasKnownLiveWrapper()) {
  39     return true;
  40   }
  41
  42   StyleSheet* sheet = GetStyleSheet();
  43   if (!sheet) {
  44     return false;
  45   }
  46
  47   Document* doc = sheet->GetKeptAliveByDocument();
  48   return doc &&
  49          nsCCUncollectableMarker::InGeneration(doc->GetMarkedCCGeneration());
  50 }
  51
  52 void Rule::UnlinkDeclarationWrapper(nsWrapperCache& aDecl) {
  53   // We have to be a bit careful here.  We have two separate nsWrapperCache
  54   // instances, aDecl and this, that both correspond to the same CC participant:
  55   // this.  If we just used ReleaseWrapper() on one of them, that would
  56   // unpreserve that one wrapper, then trace us with a tracer that clears JS
  57   // things, and we would clear the wrapper on the cache that has not
  58   // unpreserved the wrapper yet.  That would violate the invariant that the
  59   // cache keeps caching the wrapper until the wrapper dies.
  60   //
  61   // So we reimplement a modified version of nsWrapperCache::ReleaseWrapper here
  62   // that unpreserves both wrappers before doing any clearing.
  63   bool needDrop = PreservingWrapper() || aDecl.PreservingWrapper();
  64   SetPreservingWrapper(false);
  65   aDecl.SetPreservingWrapper(false);
  66   if (needDrop) {
  67     DropJSObjects(this);
  68   }
  69 }
  70
  71 NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_BEGIN(Rule)
  72   return tmp->IsCCLeaf() || tmp->IsKnownLive();
  73 NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_END
  74
  75 NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_BEGIN(Rule)
  76   // Please see documentation for nsCycleCollectionParticipant::CanSkip* for why
  77   // we need to check HasNothingToTrace here but not in the other two CanSkip
  78   // methods.
  79   return tmp->IsCCLeaf() || (tmp->IsKnownLive() && tmp->HasNothingToTrace(tmp));
  80 NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_END
  81
  82 NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_BEGIN(Rule)
  83   return tmp->IsCCLeaf() || tmp->IsKnownLive();
  84 NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_END
  85
  86 /* virtual */
  87 void Rule::DropSheetReference() { mSheet = nullptr; }
  88
  89 void Rule::SetCssText(const nsACString& aCssText) {
  90   // We used to throw for some rule types, but not all.  Specifically, we did
  91   // not throw for StyleRule.  Let's just always not throw.
  92 }
  93
  94 Rule* Rule::GetParentRule() const { return mParentRule; }
  95
  96 #ifdef DEBUG
  97 void Rule::AssertParentRuleType() {
  98   // Would be nice to check that this->Type() is KEYFRAME_RULE when
  99   // mParentRule->Tye() is KEYFRAMES_RULE, but we can't call
 100   // this->Type() here since it's virtual.
 101   if (mParentRule) {
 102     auto type = mParentRule->Type();
 103     MOZ_ASSERT(type == StyleCssRuleType::Media ||
 104                type == StyleCssRuleType::Document ||
 105                type == StyleCssRuleType::Supports ||
 106                type == StyleCssRuleType::Keyframes ||
 107                type == StyleCssRuleType::LayerBlock ||
 108                type == StyleCssRuleType::Container);
 109   }
 110 }
 111 #endif
 112
 113 bool Rule::IsReadOnly() const {
 114   MOZ_ASSERT(!mSheet || !mParentRule ||
 115                  mSheet->IsReadOnly() == mParentRule->IsReadOnly(),
 116              "a parent rule should be read only iff the owning sheet is "
 117              "read only");
 118   return mSheet && mSheet->IsReadOnly();
 119 }
 120
 121 bool Rule::IsIncompleteImportRule() const {
 122   if (Type() != StyleCssRuleType::Import) {
 123     return false;
 124   }
 125   auto* sheet = static_cast<const dom::CSSImportRule*>(this)->GetStyleSheet();
 126   return !sheet || !sheet->IsComplete();
 127 }
 128
 129 }  // namespace mozilla::css