Bug 773296 - Part 16: Add a ref-counted list nsCSSValue unit and use it for tranform lists; hold a strong reference to one on nsStyleDisplay. r=dbaron

This adds a new eCSSUnit_SharedList type for nsCSSValue, which is a
reference counted object that contains an nsCSSValueList.  We need this
so that nsStyleDisplay::mSpecifiedTransform can hold a strong reference
to a specified transform list value.  When 'transform' is specified
using a variable reference, the resulting nsCSSValue does not stick
around in the Declaration object, so we wouldn't be guaranteed that
it lives long enough for nsStyleDisplay to keep referencing it.

gfx/layers/composite/AsyncCompositionManager.cpp

@@ -40,7 +40,7 @@
 #endif
 #include "GeckoProfiler.h"
 
-struct nsCSSValueList;
+struct nsCSSValueSharedList;
 
 using namespace mozilla::dom;
 
@@ -348,7 +348,8 @@ SampleValue(float aPortion, Animation& aAnimation, nsStyleAnimation::Value& aSta
     return;
   }
 
-  nsCSSValueList* interpolatedList = interpolatedValue.GetCSSValueListValue();
+  nsCSSValueSharedList* interpolatedList =
+    interpolatedValue.GetCSSValueSharedListValue();
 
   TransformData& data = aAnimation.data().get_TransformData();
   nsPoint origin = data.origin();

layout/base/nsDisplayList.cpp

@@ -4059,7 +4059,7 @@ nsDisplayTransform::GetResultingTransformMatrixInternal(const FrameTransformProp
     frame && frame->IsSVGTransformed(&svgTransform, &transformFromSVGParent);
   /* Transformed frames always have a transform, or are preserving 3d (and might still have perspective!) */
   if (aProperties.mTransformList) {
-    result = nsStyleTransformMatrix::ReadTransforms(aProperties.mTransformList,
+    result = nsStyleTransformMatrix::ReadTransforms(aProperties.mTransformList->mHead,
                                                     frame ? frame->StyleContext() : nullptr,
                                                     frame ? frame->PresContext() : nullptr,
                                                     dummy, bounds, aAppUnitsPerPixel);

layout/base/nsDisplayList.h

@@ -3037,7 +3037,7 @@ public:
     FrameTransformProperties(const nsIFrame* aFrame,
                              float aAppUnitsPerPixel,
                              const nsRect* aBoundsOverride);
-    FrameTransformProperties(const nsCSSValueList* aTransformList,
+    FrameTransformProperties(nsCSSValueSharedList* aTransformList,
                              const gfxPoint3D& aToTransformOrigin,
                              const gfxPoint3D& aToPerspectiveOrigin,
                              nscoord aChildPerspective)
@@ -3049,7 +3049,7 @@ public:
     {}
 
     const nsIFrame* mFrame;
-    const nsCSSValueList* mTransformList;
+    nsRefPtr<nsCSSValueSharedList> mTransformList;
     const gfxPoint3D mToTransformOrigin;
     const gfxPoint3D mToPerspectiveOrigin;
     nscoord mChildPerspective;

layout/style/nsCSSParser.cpp

@@ -11179,7 +11179,10 @@ bool CSSParserImpl::ParseTransform(bool aIsPrefixed)
       return false;
     }
   } else {
-    nsCSSValueList* cur = value.SetListValue();
+    nsCSSValueSharedList* list = new nsCSSValueSharedList;
+    value.SetSharedListValue(list);
+    list->mHead = new nsCSSValueList;
+    nsCSSValueList* cur = list->mHead;
     for (;;) {
       if (!ParseSingleTransform(aIsPrefixed, cur->mValue)) {
         return false;

layout/style/nsCSSValue.cpp

@@ -162,6 +162,10 @@ nsCSSValue::nsCSSValue(const nsCSSValue& aCopy)
   else if (eCSSUnit_ListDep == mUnit) {
     mValue.mListDependent = aCopy.mValue.mListDependent;
   }
+  else if (eCSSUnit_SharedList == mUnit) {
+    mValue.mSharedList = aCopy.mValue.mSharedList;
+    mValue.mSharedList->AddRef();
+  }
   else if (eCSSUnit_PairList == mUnit) {
     mValue.mPairList = aCopy.mValue.mPairList;
     mValue.mPairList->AddRef();
@@ -232,6 +236,9 @@ bool nsCSSValue::operator==(const nsCSSValue& aOther) const
     else if (eCSSUnit_List == mUnit) {
       return *mValue.mList == *aOther.mValue.mList;
     }
+    else if (eCSSUnit_SharedList == mUnit) {
+      return *mValue.mSharedList == *aOther.mValue.mSharedList;
+    }
     else if (eCSSUnit_PairList == mUnit) {
       return *mValue.mPairList == *aOther.mValue.mPairList;
     }
@@ -315,6 +322,8 @@ void nsCSSValue::DoReset()
     mValue.mRect->Release();
   } else if (eCSSUnit_List == mUnit) {
     mValue.mList->Release();
+  } else if (eCSSUnit_SharedList == mUnit) {
+    mValue.mSharedList->Release();
   } else if (eCSSUnit_PairList == mUnit) {
     mValue.mPairList->Release();
   }
@@ -513,6 +522,14 @@ nsCSSValueList* nsCSSValue::SetListValue()
   return mValue.mList;
 }
 
+void nsCSSValue::SetSharedListValue(nsCSSValueSharedList* aList)
+{
+  Reset();
+  mUnit = eCSSUnit_SharedList;
+  mValue.mSharedList = aList;
+  mValue.mSharedList->AddRef();
+}
+
 void nsCSSValue::SetDependentListValue(nsCSSValueList* aList)
 {
   Reset();
@@ -1198,6 +1215,8 @@ nsCSSValue::AppendToString(nsCSSProperty aProperty, nsAString& aResult) const
     GetRectValue().AppendToString(aProperty, aResult);
   } else if (eCSSUnit_List == unit || eCSSUnit_ListDep == unit) {
     GetListValue()->AppendToString(aProperty, aResult);
+  } else if (eCSSUnit_SharedList == unit) {
+    GetSharedListValue()->AppendToString(aProperty, aResult);
   } else if (eCSSUnit_PairList == unit || eCSSUnit_PairListDep == unit) {
     switch (aProperty) {
       case eCSSProperty_font_feature_settings:
@@ -1258,6 +1277,7 @@ nsCSSValue::AppendToString(nsCSSProperty aProperty, nsAString& aResult) const
     case eCSSUnit_Rect:         break;
     case eCSSUnit_List:         break;
     case eCSSUnit_ListDep:      break;
+    case eCSSUnit_SharedList:   break;
     case eCSSUnit_PairList:     break;
     case eCSSUnit_PairListDep:  break;
 
@@ -1384,6 +1404,12 @@ nsCSSValue::SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
     case eCSSUnit_ListDep:
       break;
 
+    // SharedList
+    case eCSSUnit_SharedList:
+      // Makes more sense not to measure, since it most cases the list
+      // will be shared.
+      break;
+
     // PairList
     case eCSSUnit_PairList:
       n += mValue.mPairList->SizeOfIncludingThis(aMallocSizeOf);
@@ -1522,6 +1548,41 @@ nsCSSValueList_heap::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) co
   return n;
 }
 
+// --- nsCSSValueSharedList -----------------
+
+nsCSSValueSharedList::~nsCSSValueSharedList()
+{
+  MOZ_COUNT_DTOR(nsCSSValueSharedList);
+  if (mHead) {
+    NS_CSS_DELETE_LIST_MEMBER(nsCSSValueList, mHead, mNext);
+    delete mHead;
+  }
+}
+
+void
+nsCSSValueSharedList::AppendToString(nsCSSProperty aProperty, nsAString& aResult) const
+{
+  if (mHead) {
+    mHead->AppendToString(aProperty, aResult);
+  }
+}
+
+bool
+nsCSSValueSharedList::operator==(const nsCSSValueSharedList& aOther) const
+{
+  return !mHead == !aOther.mHead &&
+         (!mHead || *mHead == *aOther.mHead);
+}
+
+size_t
+nsCSSValueSharedList::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
+{
+  size_t n = 0;
+  n += aMallocSizeOf(this);
+  n += mHead->SizeOfIncludingThis(aMallocSizeOf);
+  return n;
+}
+
 // --- nsCSSRect -----------------
 
 nsCSSRect::nsCSSRect(void)

layout/style/nsCSSValue.h

@@ -197,8 +197,10 @@ enum nsCSSUnit {
   eCSSUnit_List         = 53,     // (nsCSSValueList*) list of values
   eCSSUnit_ListDep      = 54,     // (nsCSSValueList*) same as List
                                   //   but does not own the list
-  eCSSUnit_PairList     = 55,     // (nsCSSValuePairList*) list of value pairs
+  eCSSUnit_SharedList   = 55,     // (nsCSSValueSharedList*) same as list
-  eCSSUnit_PairListDep  = 56,     // (nsCSSValuePairList*) same as PairList
+                                  //   but reference counted and shared
+  eCSSUnit_PairList     = 56,     // (nsCSSValuePairList*) list of value pairs
+  eCSSUnit_PairListDep  = 57,     // (nsCSSValuePairList*) same as PairList
                                   //   but does not own the list
 
   eCSSUnit_Integer      = 70,     // (int) simple value
@@ -257,6 +259,7 @@ struct nsCSSRect;
 struct nsCSSRect_heap;
 struct nsCSSValueList;
 struct nsCSSValueList_heap;
+struct nsCSSValueSharedList;
 struct nsCSSValuePairList;
 struct nsCSSValuePairList_heap;
 struct nsCSSValueTriplet;
@@ -430,6 +433,12 @@ public:
     return mValue.mTokenStream;
   }
 
+  nsCSSValueSharedList* GetSharedListValue() const
+  {
+    NS_ABORT_IF_FALSE(mUnit == eCSSUnit_SharedList, "not a shared list value");
+    return mValue.mSharedList;
+  }
+
   // bodies of these are below
   inline nsCSSValuePair& GetPairValue();
   inline const nsCSSValuePair& GetPairValue() const;
@@ -498,6 +507,7 @@ public:
   void SetTokenStreamValue(nsCSSValueTokenStream* aTokenStream);
   void SetPairValue(const nsCSSValuePair* aPair);
   void SetPairValue(const nsCSSValue& xValue, const nsCSSValue& yValue);
+  void SetSharedListValue(nsCSSValueSharedList* aList);
   void SetDependentListValue(nsCSSValueList* aList);
   void SetDependentPairListValue(nsCSSValuePairList* aList);
   void SetTripletValue(const nsCSSValueTriplet* aTriplet);
@@ -557,6 +567,7 @@ protected:
     nsCSSValueTriplet_heap* mTriplet;
     nsCSSValueList_heap* mList;
     nsCSSValueList* mListDependent;
+    nsCSSValueSharedList* mSharedList;
     nsCSSValuePairList_heap* mPairList;
     nsCSSValuePairList* mPairListDependent;
   } mValue;
@@ -701,6 +712,38 @@ struct nsCSSValueList_heap : public nsCSSValueList {
   size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
 };
 
+// This is a reference counted list value.  Note that the object is
+// a wrapper for the reference count and a pointer to the head of the
+// list, whereas the other list types (such as nsCSSValueList) do
+// not have such a wrapper.
+struct nsCSSValueSharedList {
+  nsCSSValueSharedList()
+  {
+    MOZ_COUNT_CTOR(nsCSSValueSharedList);
+  }
+
+  // Takes ownership of aList.
+  nsCSSValueSharedList(nsCSSValueList* aList)
+    : mHead(aList)
+  {
+    MOZ_COUNT_CTOR(nsCSSValueSharedList);
+  }
+
+  ~nsCSSValueSharedList();
+
+  NS_INLINE_DECL_REFCOUNTING(nsCSSValueSharedList)
+
+  void AppendToString(nsCSSProperty aProperty, nsAString& aResult) const;
+
+  bool operator==(nsCSSValueSharedList const& aOther) const;
+  bool operator!=(const nsCSSValueSharedList& aOther) const
+  { return !(*this == aOther); }
+
+  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+  nsCSSValueList* mHead;
+};
+
 // This has to be here so that the relationship between nsCSSValueList
 // and nsCSSValueList_heap is visible.
 inline nsCSSValueList*

layout/style/nsComputedDOMStyle.cpp

@@ -1232,7 +1232,7 @@ nsComputedDOMStyle::DoGetTransform()
 
    bool dummy;
    gfx3DMatrix matrix =
-     nsStyleTransformMatrix::ReadTransforms(display->mSpecifiedTransform,
+     nsStyleTransformMatrix::ReadTransforms(display->mSpecifiedTransform->mHead,
                                             mStyleContextHolder,
                                             mStyleContextHolder->PresContext(),
                                             dummy,

layout/style/nsRuleNode.cpp

@@ -5354,15 +5354,16 @@ nsRuleNode::ComputeDisplayData(void* aStartStruct,
     canStoreInRuleTree = false;
     break;
 
-  case eCSSUnit_List:
+  case eCSSUnit_SharedList: {
-  case eCSSUnit_ListDep: {
+    nsCSSValueSharedList* list = transformValue->GetSharedListValue();
-    const nsCSSValueList* head = transformValue->GetListValue();
+    nsCSSValueList* head = list->mHead;
+    MOZ_ASSERT(head, "transform list must have at least one item");
     // can get a _None in here from transform animation
     if (head->mValue.GetUnit() == eCSSUnit_None) {
       NS_ABORT_IF_FALSE(head->mNext == nullptr, "none must be alone");
       display->mSpecifiedTransform = nullptr;
     } else {
-      display->mSpecifiedTransform = head; // weak pointer, owned by rule
+      display->mSpecifiedTransform = list;
     }
     break;
   }

layout/style/nsStyleAnimation.cpp

@@ -2277,8 +2277,11 @@ nsStyleAnimation::AddWeighted(nsCSSProperty aProperty,
     }
 
     case eUnit_Transform: {
-      const nsCSSValueList *list1 = aValue1.GetCSSValueListValue();
+      const nsCSSValueList* list1 = aValue1.GetCSSValueSharedListValue()->mHead;
-      const nsCSSValueList *list2 = aValue2.GetCSSValueListValue();
+      const nsCSSValueList* list2 = aValue2.GetCSSValueSharedListValue()->mHead;
+
+      MOZ_ASSERT(list1);
+      MOZ_ASSERT(list2);
 
       // We want to avoid the matrix decomposition when we can, since
       // avoiding it can produce better results both for compound
@@ -2332,8 +2335,7 @@ nsStyleAnimation::AddWeighted(nsCSSProperty aProperty,
         }
       }
 
-      aResultValue.SetAndAdoptCSSValueListValue(result.forget(),
+      aResultValue.SetTransformValue(new nsCSSValueSharedList(result.forget()));
-                                                eUnit_Transform);
       return true;
     }
     case eUnit_BackgroundPosition: {
@@ -2649,11 +2651,14 @@ nsStyleAnimation::UncomputeValue(nsCSSProperty aProperty,
     case eUnit_Dasharray:
     case eUnit_Shadow:
     case eUnit_Filter:
-    case eUnit_Transform:
     case eUnit_BackgroundPosition:
       aSpecifiedValue.
         SetDependentListValue(aComputedValue.GetCSSValueListValue());
       break;
+    case eUnit_Transform:
+      aSpecifiedValue.
+        SetSharedListValue(aComputedValue.GetCSSValueSharedListValue());
+      break;
     case eUnit_CSSValuePairList:
       aSpecifiedValue.
         SetDependentPairListValue(aComputedValue.GetCSSValuePairListValue());
@@ -3308,7 +3313,7 @@ nsStyleAnimation::ExtractComputedValue(nsCSSProperty aProperty,
           if (display->mSpecifiedTransform) {
             // Clone, and convert all lengths (not percents) to pixels.
             nsCSSValueList **resultTail = getter_Transfers(result);
-            for (const nsCSSValueList *l = display->mSpecifiedTransform;
+            for (const nsCSSValueList *l = display->mSpecifiedTransform->mHead;
                  l; l = l->mNext) {
               nsCSSValueList *clone = new nsCSSValueList;
               *resultTail = clone;
@@ -3321,8 +3326,8 @@ nsStyleAnimation::ExtractComputedValue(nsCSSProperty aProperty,
             result->mValue.SetNoneValue();
           }
 
-          aComputedValue.SetAndAdoptCSSValueListValue(result.forget(),
+          aComputedValue.SetTransformValue(
-                                                      eUnit_Transform);
+              new nsCSSValueSharedList(result.forget()));
           break;
         }
 
@@ -3568,7 +3573,6 @@ nsStyleAnimation::Value::operator=(const Value& aOther)
     case eUnit_Filter:
     case eUnit_Dasharray:
     case eUnit_Shadow:
-    case eUnit_Transform:
     case eUnit_BackgroundPosition:
       NS_ABORT_IF_FALSE(mUnit == eUnit_Shadow || mUnit == eUnit_Filter ||
                         aOther.mValue.mCSSValueList,
@@ -3582,6 +3586,10 @@ nsStyleAnimation::Value::operator=(const Value& aOther)
         mValue.mCSSValueList = nullptr;
       }
       break;
+    case eUnit_Transform:
+      mValue.mCSSValueSharedList = aOther.mValue.mCSSValueSharedList;
+      mValue.mCSSValueSharedList->AddRef();
+      break;
     case eUnit_CSSValuePairList:
       NS_ABORT_IF_FALSE(aOther.mValue.mCSSValuePairList,
                         "value pair lists may not be null");
@@ -3728,6 +3736,15 @@ nsStyleAnimation::Value::SetAndAdoptCSSValueListValue(
   mValue.mCSSValueList = aValueList; // take ownership
 }
 
+void
+nsStyleAnimation::Value::SetTransformValue(nsCSSValueSharedList* aList)
+{
+  FreeValue();
+  mUnit = eUnit_Transform;
+  mValue.mCSSValueSharedList = aList;
+  mValue.mCSSValueSharedList->AddRef();
+}
+
 void
 nsStyleAnimation::Value::SetAndAdoptCSSValuePairListValue(
                            nsCSSValuePairList *aValuePairList)
@@ -3745,6 +3762,8 @@ nsStyleAnimation::Value::FreeValue()
     delete mValue.mCSSValue;
   } else if (IsCSSValueListUnit(mUnit)) {
     delete mValue.mCSSValueList;
+  } else if (IsCSSValueSharedListValue(mUnit)) {
+    mValue.mCSSValueSharedList->Release();
   } else if (IsCSSValuePairUnit(mUnit)) {
     delete mValue.mCSSValuePair;
   } else if (IsCSSValueTripletUnit(mUnit)) {
@@ -3794,9 +3813,10 @@ nsStyleAnimation::Value::operator==(const Value& aOther) const
     case eUnit_Dasharray:
     case eUnit_Filter:
     case eUnit_Shadow:
-    case eUnit_Transform:
     case eUnit_BackgroundPosition:
       return *mValue.mCSSValueList == *aOther.mValue.mCSSValueList;
+    case eUnit_Transform:
+      return *mValue.mCSSValueSharedList == *aOther.mValue.mCSSValueSharedList;
     case eUnit_CSSValuePairList:
       return *mValue.mCSSValuePairList == *aOther.mValue.mCSSValuePairList;
     case eUnit_UnparsedString:

layout/style/nsStyleAnimation.h

@@ -242,6 +242,7 @@ public:
       nsCSSValueTriplet* mCSSValueTriplet;
       nsCSSRect* mCSSRect;
       nsCSSValueList* mCSSValueList;
+      nsCSSValueSharedList* mCSSValueSharedList;
       nsCSSValuePairList* mCSSValuePairList;
       nsStringBuffer* mString;
     } mValue;
@@ -297,6 +298,10 @@ public:
       NS_ASSERTION(IsCSSValueListUnit(mUnit), "unit mismatch");
       return mValue.mCSSValueList;
     }
+    nsCSSValueSharedList* GetCSSValueSharedListValue() const {
+      NS_ASSERTION(IsCSSValueSharedListValue(mUnit), "unit mismatch");
+      return mValue.mCSSValueSharedList;
+    }
     nsCSSValuePairList* GetCSSValuePairListValue() const {
       NS_ASSERTION(IsCSSValuePairListUnit(mUnit), "unit mismatch");
       return mValue.mCSSValuePairList;
@@ -351,6 +356,8 @@ public:
     void SetAndAdoptCSSValueListValue(nsCSSValueList *aValue, Unit aUnit);
     void SetAndAdoptCSSValuePairListValue(nsCSSValuePairList *aValue);
 
+    void SetTransformValue(nsCSSValueSharedList* aList);
+
     Value& operator=(const Value& aOther);
 
     bool operator==(const Value& aOther) const;
@@ -382,9 +389,12 @@ public:
     }
     static bool IsCSSValueListUnit(Unit aUnit) {
       return aUnit == eUnit_Dasharray || aUnit == eUnit_Filter ||
-             aUnit == eUnit_Shadow || aUnit == eUnit_Transform ||
+             aUnit == eUnit_Shadow ||
              aUnit == eUnit_BackgroundPosition;
     }
+    static bool IsCSSValueSharedListValue(Unit aUnit) {
+      return aUnit == eUnit_Transform;
+    }
     static bool IsCSSValuePairListUnit(Unit aUnit) {
       return aUnit == eUnit_CSSValuePairList;
     }

layout/style/nsStyleStruct.h

@@ -1724,10 +1724,10 @@ struct nsStyleDisplay {
   // mSpecifiedTransform is the list of transform functions as
   // specified, or null to indicate there is no transform.  (inherit or
   // initial are replaced by an actual list of transform functions, or
-  // null, as appropriate.) (owned by the style rule)
+  // null, as appropriate.)
   uint8_t mBackfaceVisibility;
   uint8_t mTransformStyle;
-  const nsCSSValueList *mSpecifiedTransform; // [reset]
+  nsRefPtr<nsCSSValueSharedList> mSpecifiedTransform; // [reset]
   nsStyleCoord mTransformOrigin[3]; // [reset] percent, coord, calc, 3rd param is coord, calc only
   nsStyleCoord mChildPerspective; // [reset] coord
   nsStyleCoord mPerspectiveOrigin[2]; // [reset] percent, coord, calc