Jan-Niklas Jaeschke
20536e9c57
Differential Revision: https://phabricator.services.mozilla.com/D286299
103 lines
3.5 KiB
C++
103 lines
3.5 KiB
C++
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_CachedInheritingStyles_h
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#define mozilla_CachedInheritingStyles_h
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#include "nsAtom.h"
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#include "nsCOMPtr.h"
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#include "nsTArray.h"
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class nsWindowSizes;
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namespace mozilla {
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struct PseudoStyleRequest;
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enum class PseudoStyleType : uint8_t;
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class ComputedStyle;
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// Entry in the cached inheriting styles cache. Stores the style and, for
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// functional pseudo-elements like ::highlight(name), the functional parameter.
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// mStyle may be null for entries that record a lazy pseudo probe that returned
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// no matching rules.
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struct CachedStyleEntry {
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RefPtr<ComputedStyle> mStyle;
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RefPtr<nsAtom> mFunctionalPseudoParameter;
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PseudoStyleType mPseudoType;
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};
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// Cache of anonymous box and lazy pseudo styles that inherit from a given
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// style.
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//
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// To minimize memory footprint, the cache is word-sized with a tagged pointer.
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// mBits encoding (low two bits are tags):
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// mBits == 0: empty
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// mBits & 1 == 1: indirect (pointer to IndirectCache with bit 0 set)
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// mBits & 3 == 2: null-direct — a single cached null probe result,
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// with PseudoStyleType stored in bits [2..N]
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// mBits & 3 == 0, != 0: direct — pointer to a single ComputedStyle
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//
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// See bug 1429126 comment 0 and comment 1 for the measurements and
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// rationale that influenced the design.
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class CachedInheritingStyles {
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public:
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// aStyle may be null to record a "null entry" for a lazy pseudo probe that
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// returned no matching rules.
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void Insert(ComputedStyle* aStyle, PseudoStyleType aType,
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nsAtom* aFunctionalPseudoParameter = nullptr);
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ComputedStyle* Lookup(const PseudoStyleRequest& aRequest) const;
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// Returns true if any entry (null or non-null) exists for the given request.
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bool HasEntry(const PseudoStyleRequest& aRequest) const;
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// Appends all cached styles to the given array.
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// Skips null entries.
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void AppendTo(nsTArray<const ComputedStyle*>& aArray) const;
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// Calls aFunc(ComputedStyle*, nsAtom*, PseudoStyleType) for each
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// lazily-cascaded pseudo element entry (null or non-null). Anon box entries
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// are skipped. The ComputedStyle* and nsAtom* are non-owning.
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template <typename Func>
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void ForEachLazyPseudoEntry(Func&& aFunc) const;
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CachedInheritingStyles() : mBits(0) {}
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~CachedInheritingStyles() {
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if (IsIndirect()) {
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delete AsIndirect();
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} else if (!IsEmpty() && !IsNullDirect()) {
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RefPtr<ComputedStyle> ref = dont_AddRef(AsDirect());
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}
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}
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void AddSizeOfIncludingThis(nsWindowSizes& aSizes, size_t* aCVsSize) const;
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private:
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// See bug 1429126 comment 1 for the choice of four here.
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using IndirectCache = AutoTArray<CachedStyleEntry, 4>;
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bool IsEmpty() const { return !mBits; }
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bool IsIndirect() const { return (mBits & 1); }
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bool IsNullDirect() const { return (mBits & 3) == 2; }
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ComputedStyle* AsDirect() const {
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MOZ_ASSERT(!IsIndirect() && !IsNullDirect());
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return reinterpret_cast<ComputedStyle*>(mBits);
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}
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PseudoStyleType NullDirectType() const {
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MOZ_ASSERT(IsNullDirect());
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return static_cast<PseudoStyleType>(mBits >> 2);
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}
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IndirectCache* AsIndirect() const {
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MOZ_ASSERT(IsIndirect());
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return reinterpret_cast<IndirectCache*>(mBits & ~uintptr_t(1));
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}
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uintptr_t mBits;
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};
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} // namespace mozilla
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#endif // mozilla_CachedInheritingStyles_h
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