/* -*- 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/. */

#ifndef mozilla_CachedInheritingStyles_h

#define mozilla_CachedInheritingStyles_h

#include "nsAtom.h"

#include "nsCOMPtr.h"

#include "nsTArray.h"

class nsWindowSizes;

namespace mozilla {

class ComputedStyle;

// 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

// If there is only one entry, it's stored inline. If there are more, they're

// stored in an out-of-line buffer. See bug 1429126 comment 0 and comment 1 for

// the measurements and rationale that influenced the design.

class CachedInheritingStyles

{

public:

  void Insert(ComputedStyle* aStyle);

  ComputedStyle* Lookup(nsAtom* aPseudoTag) const;

  CachedInheritingStyles() : mBits(0) {}

  ~CachedInheritingStyles()

  {

    if (IsIndirect()) {

      delete AsIndirect();

    } else if (!IsEmpty()) {

      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.

  typedef AutoTArray<RefPtr<ComputedStyle>, 4> IndirectCache;

  bool IsEmpty() const { return !mBits; }

  bool IsIndirect() const { return (mBits & 1); }

  ComputedStyle* AsDirect() const

  {

    MOZ_ASSERT(!IsIndirect());

    return reinterpret_cast<ComputedStyle*>(mBits);

  }

  IndirectCache* AsIndirect() const

  {

    MOZ_ASSERT(IsIndirect());

    return reinterpret_cast<IndirectCache*>(mBits & ~1);

  }

  uintptr_t mBits;

};

} // namespace mozilla

#endif // mozilla_CachedInheritingStyles_h