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/* 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/. */
#ifndef mozilla_CachedInheritingStyles_h
#define mozilla_CachedInheritingStyles_h
#include "nsAtom.h"
#include "nsCOMPtr.h"
#include "nsTArray.h"
class nsWindowSizes;
namespace mozilla {
struct PseudoStyleRequest;
enum class PseudoStyleType : uint8_t;
class ComputedStyle;
// Entry in the cached inheriting styles cache. Stores the style and, for
// functional pseudo-elements like ::highlight(name), the functional parameter.
// mStyle may be null for entries that record a lazy pseudo probe that returned
// no matching rules.
struct CachedStyleEntry {
RefPtr<ComputedStyle> mStyle;
RefPtr<nsAtom> mFunctionalPseudoParameter;
PseudoStyleType mPseudoType;
};
// Cache of anonymous box and lazy pseudo styles that inherit from a given
// style.
//
// To minimize memory footprint, the cache is word-sized with a tagged pointer.
// mBits encoding (low two bits are tags):
// mBits == 0: empty
// mBits & 1 == 1: indirect (pointer to IndirectCache with bit 0 set)
// mBits & 3 == 2: null-direct — a single cached null probe result,
// with PseudoStyleType stored in bits [2..N]
// mBits & 3 == 0, != 0: direct — pointer to a single ComputedStyle
//
// See bug 1429126 comment 0 and comment 1 for the measurements and
// rationale that influenced the design.
class CachedInheritingStyles {
public:
// aStyle may be null to record a "null entry" for a lazy pseudo probe that
// returned no matching rules.
void Insert(ComputedStyle* aStyle, PseudoStyleType aType,
nsAtom* aFunctionalPseudoParameter = nullptr);
ComputedStyle* Lookup(const PseudoStyleRequest& aRequest) const;
// Returns true if any entry (null or non-null) exists for the given request.
bool HasEntry(const PseudoStyleRequest& aRequest) const;
// Appends all cached styles to the given array.
// Skips null entries.
void AppendTo(nsTArray<const ComputedStyle*>& aArray) const;
// Appends all cached entries (with functional parameters) to the given array.
// Includes null entries.
void AppendEntriesTo(nsTArray<CachedStyleEntry>& aArray) const;
CachedInheritingStyles() : mBits(0) {}
~CachedInheritingStyles() {
if (IsIndirect()) {
delete AsIndirect();
} else if (!IsEmpty() && !IsNullDirect()) {
RefPtr<ComputedStyle> ref = dont_AddRef(AsDirect());
}
}
void AddSizeOfIncludingThis(nsWindowSizes& aSizes, size_t* aCVsSize) const;
private:
// See bug 1429126 comment 1 for the choice of four here.
using IndirectCache = AutoTArray<CachedStyleEntry, 4>;
bool IsEmpty() const { return !mBits; }
bool IsIndirect() const { return (mBits & 1); }
bool IsNullDirect() const { return (mBits & 3) == 2; }
ComputedStyle* AsDirect() const {
MOZ_ASSERT(!IsIndirect() && !IsNullDirect());
return reinterpret_cast<ComputedStyle*>(mBits);
}
PseudoStyleType NullDirectType() const {
MOZ_ASSERT(IsNullDirect());
return static_cast<PseudoStyleType>(mBits >> 2);
}
IndirectCache* AsIndirect() const {
MOZ_ASSERT(IsIndirect());
return reinterpret_cast<IndirectCache*>(mBits & ~uintptr_t(1));
}
uintptr_t mBits;
};
} // namespace mozilla
#endif // mozilla_CachedInheritingStyles_h