nsTreeStyleCache.h (2646B)
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ 3 /* This Source Code Form is subject to the terms of the Mozilla Public 4 * License, v. 2.0. If a copy of the MPL was not distributed with this 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 6 7 #ifndef nsTreeStyleCache_h__ 8 #define nsTreeStyleCache_h__ 9 10 #include "mozilla/AtomArray.h" 11 #include "mozilla/ComputedStyle.h" 12 #include "mozilla/UniquePtr.h" 13 #include "nsCOMArray.h" 14 #include "nsRefPtrHashtable.h" 15 #include "nsTHashMap.h" 16 17 class nsIContent; 18 19 class nsTreeStyleCache { 20 public: 21 nsTreeStyleCache() : mNextState(0) {} 22 23 ~nsTreeStyleCache() { Clear(); } 24 25 void Clear() { 26 mTransitionTable = nullptr; 27 mCache = nullptr; 28 mNextState = 0; 29 } 30 31 mozilla::ComputedStyle* GetComputedStyle( 32 nsPresContext* aPresContext, nsIContent* aContent, 33 mozilla::ComputedStyle* aStyle, 34 nsCSSAnonBoxPseudoStaticAtom* aPseudoElement, 35 const mozilla::AtomArray& aInputWord); 36 37 protected: 38 typedef uint32_t DFAState; 39 40 class Transition final { 41 public: 42 Transition(DFAState aState, nsAtom* aSymbol); 43 bool operator==(const Transition& aOther) const; 44 uint32_t Hash() const; 45 46 private: 47 DFAState mState; 48 RefPtr<nsAtom> mInputSymbol; 49 }; 50 51 typedef nsTHashMap<nsGenericHashKey<Transition>, DFAState> TransitionTable; 52 53 // A transition table for a deterministic finite automaton. The DFA 54 // takes as its input a single pseudoelement and an ordered set of properties. 55 // It transitions on an input word that is the concatenation of the 56 // pseudoelement supplied with the properties in the array. 57 // 58 // It transitions from state to state by looking up entries in the transition 59 // table (which is a mapping from (S,i)->S', where S is the current state, i 60 // is the next property in the input word, and S' is the state to transition 61 // to. 62 // 63 // If S' is not found, it is constructed and entered into the hashtable 64 // under the key (S,i). 65 // 66 // Once the entire word has been consumed, the final state is used 67 // to reference the cache table to locate the ComputedStyle. 68 mozilla::UniquePtr<TransitionTable> mTransitionTable; 69 70 // The cache of all active ComputedStyles. This is a hash from 71 // a final state in the DFA, Sf, to the resultant ComputedStyle. 72 typedef nsRefPtrHashtable<nsUint32HashKey, mozilla::ComputedStyle> 73 ComputedStyleCache; 74 mozilla::UniquePtr<ComputedStyleCache> mCache; 75 76 // An integer counter that is used when we need to make new states in the 77 // DFA. 78 DFAState mNextState; 79 }; 80 81 #endif // nsTreeStyleCache_h__