nsTreeStyleCache.h

Enable keyboard shortcuts

/* -*- 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 nsTreeStyleCache_h__

#define nsTreeStyleCache_h__

#include "mozilla/AtomArray.h"

#include "mozilla/Attributes.h"

#include "mozilla/UniquePtr.h"

#include "nsCOMArray.h"

#include "nsTHashMap.h"

#include "nsRefPtrHashtable.h"

#include "mozilla/ComputedStyle.h"

class nsIContent;

class nsTreeStyleCache {

 public:

  nsTreeStyleCache() : mNextState(0) {}

  ~nsTreeStyleCache() { Clear(); }

  void Clear() {

    mTransitionTable = nullptr;

    mCache = nullptr;

    mNextState = 0;

  mozilla::ComputedStyle* GetComputedStyle(

      nsPresContext* aPresContext, nsIContent* aContent,

      mozilla::ComputedStyle* aStyle,

      nsCSSAnonBoxPseudoStaticAtom* aPseudoElement,

      const mozilla::AtomArray& aInputWord);

 protected:

  typedef uint32_t DFAState;

  class Transition final {

   public:

    Transition(DFAState aState, nsAtom* aSymbol);

    bool operator==(const Transition& aOther) const;

    uint32_t Hash() const;

   private:

    DFAState mState;

    RefPtr<nsAtom> mInputSymbol;

};

  typedef nsTHashMap<nsGenericHashKey<Transition>, DFAState> TransitionTable;

  // A transition table for a deterministic finite automaton.  The DFA

  // takes as its input a single pseudoelement and an ordered set of properties.

  // It transitions on an input word that is the concatenation of the

  // pseudoelement supplied with the properties in the array.

//

  // It transitions from state to state by looking up entries in the transition

  // table (which is a mapping from (S,i)->S', where S is the current state, i

  // is the next property in the input word, and S' is the state to transition

  // to.

//

  // If S' is not found, it is constructed and entered into the hashtable

  // under the key (S,i).

//

  // Once the entire word has been consumed, the final state is used

  // to reference the cache table to locate the ComputedStyle.

  mozilla::UniquePtr<TransitionTable> mTransitionTable;

  // The cache of all active ComputedStyles.  This is a hash from

  // a final state in the DFA, Sf, to the resultant ComputedStyle.

  typedef nsRefPtrHashtable<nsUint32HashKey, mozilla::ComputedStyle>

      ComputedStyleCache;

  mozilla::UniquePtr<ComputedStyleCache> mCache;

  // An integer counter that is used when we need to make new states in the

  // DFA.

  DFAState mNextState;

};

#endif  // nsTreeStyleCache_h__