/* -*- 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 DISPLAYITEMCLIPCHAIN_H_

#define DISPLAYITEMCLIPCHAIN_H_

#include "mozilla/Assertions.h"

#include "DisplayItemClip.h"

#include "nsString.h"

class nsIScrollableFrame;

namespace mozilla {

struct ActiveScrolledRoot;

/**

 * A DisplayItemClipChain is a linked list of DisplayItemClips where each clip

 * is associated with an active scrolled root that describes what the clip

 * moves with.

 * We use a chain instead of just one intersected clip due to async scrolling:

 * A clip that moves along with a display item can be fused to the item's

 * contents when drawing the layer contents, but all other clips in the chain

 * need to be kept separate so that they can be applied at composition time,

 * after any async scroll offsets have been applied.

 * The clip chain is created during display list construction by the builder's

 * DisplayListClipState.

 * The clip chain order is determined by the active scrolled root order.

 * For every DisplayItemClipChain object |clipChain|, the following holds:

 * !clipChain->mParent ||

 * ActiveScrolledRoot::IsAncestor(clipChain->mParent->mASR, clipChain->mASR).

 * The clip chain can skip over active scrolled roots. That just means that

 * there is no clip that moves with the skipped ASR in this chain.

 */

struct DisplayItemClipChain

{

  /**

   * Get the display item clip in this chain that moves with aASR, or nullptr

   * if no such clip exists. aClipChain can be null.

   */

  static const DisplayItemClip* ClipForASR(

    const DisplayItemClipChain* aClipChain,

    const ActiveScrolledRoot* aASR);

  static bool Equal(const DisplayItemClipChain* aClip1,

                    const DisplayItemClipChain* aClip2);

  /**

   * Hash function that returns the same value for any two clips A and B

   * where Equal(A, B) is true.

   */

  static uint32_t Hash(const DisplayItemClipChain* aClip);

  static nsCString ToString(const DisplayItemClipChain* aClipChain);

  bool HasRoundedCorners() const;

  void AddRef() { mRefCount++; }

  void Release()

  {

    MOZ_ASSERT(mRefCount > 0);

    mRefCount--;

  }

  DisplayItemClipChain(const DisplayItemClip& aClip,

                       const ActiveScrolledRoot* aASR,

                       const DisplayItemClipChain* aParent,

                       DisplayItemClipChain* aNextClipChainToDestroy)

    : mClip(aClip)

    , mASR(aASR)

    , mParent(aParent)

    , mNextClipChainToDestroy(aNextClipChainToDestroy)

#ifdef DEBUG

    , mOnStack(true)

#endif

  {

  }

  DisplayItemClipChain()

    : mASR(nullptr)

    , mNextClipChainToDestroy(nullptr)

#ifdef DEBUG

    , mOnStack(true)

#endif

  {

  }

  DisplayItemClip mClip;

  const ActiveScrolledRoot* mASR;

  RefPtr<const DisplayItemClipChain> mParent;

  uint32_t mRefCount = 0;

  DisplayItemClipChain* mNextClipChainToDestroy;

#ifdef DEBUG

  bool mOnStack;

#endif

};

struct DisplayItemClipChainHasher

{

  typedef const DisplayItemClipChain* Key;

  std::size_t operator()(const Key& aKey) const

  {

    return DisplayItemClipChain::Hash(aKey);

  }

};

struct DisplayItemClipChainEqualer

{

  typedef const DisplayItemClipChain* Key;

  bool operator()(const Key& lhs, const Key& rhs) const

  {

    return DisplayItemClipChain::Equal(lhs, rhs);

  }

};

} // namespace mozilla

#endif /* DISPLAYITEMCLIPCHAIN_H_ */