gecko/layout/style/RuleProcessorCache.h

/* -*- 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/. */

/*
 * cache of re-usable nsCSSRuleProcessors for given sets of style sheets
 */

#ifndef mozilla_RuleProcessorCache_h
#define mozilla_RuleProcessorCache_h

#include "mozilla/MemoryReporting.h"
#include "mozilla/StaticPtr.h"
#include "nsCSSRuleProcessor.h"
#include "nsExpirationTracker.h"
#include "nsIMediaList.h"
#include "nsIMemoryReporter.h"
#include "nsTArray.h"

class nsCSSRuleProcessor;
namespace mozilla {
class CSSStyleSheet;
namespace css {
class DocumentRule;
} // namespace css
} // namespace mozilla

namespace mozilla {

/**
 * The RuleProcessorCache is a singleton object that caches
 * nsCSSRuleProcessors keyed off a list of style sheets and the result of
 * evaluating all @-moz-documents in the style sheets.  nsStyleSet gets and
 * puts nsCSSRuleProcessors from/to the RuleProcessorCache.
 *
 * State bits on CSSStyleSheet and nsCSSRuleProcessor track whether they are in
 * the RuleProcessorCache.  This lets us remove them from the RuleProcessorCache
 * when they're going away.
 */
class RuleProcessorCache final : public nsIMemoryReporter
{
  NS_DECL_ISUPPORTS
  NS_DECL_NSIMEMORYREPORTER

public:
  static nsCSSRuleProcessor* GetRuleProcessor(
      const nsTArray<CSSStyleSheet*>& aSheets,
      nsPresContext* aPresContext);
  static void PutRuleProcessor(
      const nsTArray<CSSStyleSheet*>& aSheets,
      nsTArray<css::DocumentRule*>&& aDocumentRulesInSheets,
      const nsDocumentRuleResultCacheKey& aCacheKey,
      nsCSSRuleProcessor* aRuleProcessor);
  static void StartTracking(nsCSSRuleProcessor* aRuleProcessor);
  static void StopTracking(nsCSSRuleProcessor* aRuleProcessor);

#ifdef DEBUG
  static bool HasRuleProcessor(nsCSSRuleProcessor* aRuleProcessor);
#endif
  static void RemoveRuleProcessor(nsCSSRuleProcessor* aRuleProcessor);
  static void RemoveSheet(CSSStyleSheet* aSheet);

  static void Shutdown() { gShutdown = true; gRuleProcessorCache = nullptr; }

  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf);

private:
  class ExpirationTracker : public nsExpirationTracker<nsCSSRuleProcessor,3>
  {
  public:
    explicit ExpirationTracker(RuleProcessorCache* aCache)
      : nsExpirationTracker<nsCSSRuleProcessor,3>(10000)
      , mCache(aCache) {}

    void RemoveObjectIfTracked(nsCSSRuleProcessor* aRuleProcessor);

    virtual void NotifyExpired(nsCSSRuleProcessor* aRuleProcessor) override {
      mCache->RemoveRuleProcessor(aRuleProcessor);
    }

  private:
    RuleProcessorCache* mCache;
  };

  RuleProcessorCache() : mExpirationTracker(this) {}
  ~RuleProcessorCache();

  void InitMemoryReporter();

  static bool EnsureGlobal();
  static StaticRefPtr<RuleProcessorCache> gRuleProcessorCache;
  static bool gShutdown;

  void DoRemoveSheet(CSSStyleSheet* aSheet);
  nsCSSRuleProcessor* DoGetRuleProcessor(
      const nsTArray<CSSStyleSheet*>& aSheets,
      nsPresContext* aPresContext);
  void DoPutRuleProcessor(const nsTArray<CSSStyleSheet*>& aSheets,
                          nsTArray<css::DocumentRule*>&& aDocumentRulesInSheets,
                          const nsDocumentRuleResultCacheKey& aCacheKey,
                          nsCSSRuleProcessor* aRuleProcessor);
#ifdef DEBUG
  bool DoHasRuleProcessor(nsCSSRuleProcessor* aRuleProcessor);
#endif
  void DoRemoveRuleProcessor(nsCSSRuleProcessor* aRuleProcessor);
  void DoStartTracking(nsCSSRuleProcessor* aRuleProcessor);
  void DoStopTracking(nsCSSRuleProcessor* aRuleProcessor);

  struct DocumentEntry {
    nsDocumentRuleResultCacheKey mCacheKey;
    nsRefPtr<nsCSSRuleProcessor> mRuleProcessor;
  };

  struct Entry {
    nsTArray<CSSStyleSheet*>     mSheets;
    nsTArray<css::DocumentRule*> mDocumentRulesInSheets;
    nsTArray<DocumentEntry>      mDocumentEntries;
  };

  // Function object to test whether an Entry object has a given sheet
  // in its mSheets array.  If it does, removes all of its rule processors
  // before returning true.
  struct HasSheet_ThenRemoveRuleProcessors {
    HasSheet_ThenRemoveRuleProcessors(RuleProcessorCache* aCache,
                                      CSSStyleSheet* aSheet)
      : mCache(aCache), mSheet(aSheet) {}
    bool operator()(Entry& aEntry) {
      if (aEntry.mSheets.Contains(mSheet)) {
        for (DocumentEntry& de : aEntry.mDocumentEntries) {
          de.mRuleProcessor->SetInRuleProcessorCache(false);
          mCache->mExpirationTracker.RemoveObjectIfTracked(de.mRuleProcessor);
        }
        return true;
      }
      return false;
    }
    RuleProcessorCache* mCache;
    CSSStyleSheet* mSheet;
  };

  ExpirationTracker mExpirationTracker;
  nsTArray<Entry> mEntries;
};

} // namespace mozilla

#endif // mozilla_RuleProcessorCache_h