tor-browser

The Tor Browser
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ScrollGeneration.h (1926B)

      1 /* This Source Code Form is subject to the terms of the Mozilla Public
      2 * License, v. 2.0. If a copy of the MPL was not distributed with this
      3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      4 
      5 #ifndef mozilla_ScrollGeneration_h_
      6 #define mozilla_ScrollGeneration_h_
      7 
      8 #include <cstdint>
      9 #include <iosfwd>
     10 #include <tuple>
     11 
     12 namespace mozilla {
     13 
     14 struct ScrollGenerationCounter;
     15 
     16 class APZTag {};
     17 class MainThreadTag {};
     18 
     19 template <typename Tag>
     20 struct ScrollGeneration;
     21 
     22 template <typename Tag>
     23 std::ostream& operator<<(std::ostream& aStream,
     24                         const ScrollGeneration<Tag>& aGen);
     25 
     26 template <typename Tag>
     27 struct ScrollGeneration final {
     28  friend struct ScrollGenerationCounter;
     29 
     30 private:
     31  // Private constructor; use ScrollGenerationCounter to get a new instance.
     32  explicit ScrollGeneration(uint64_t aValue);
     33 
     34 public:
     35  // Dummy constructor, needed for IPDL purposes. Not intended for manual use.
     36  ScrollGeneration();
     37 
     38  uint64_t Raw() const { return mValue; }
     39 
     40  bool operator<(const ScrollGeneration<Tag>& aOther) const;
     41  bool operator==(const ScrollGeneration<Tag>& aOther) const;
     42  bool operator!=(const ScrollGeneration<Tag>& aOther) const;
     43 
     44  friend std::ostream& operator<< <>(std::ostream& aStream,
     45                                     const ScrollGeneration<Tag>& aGen);
     46 
     47  auto MutTiedFields() { return std::tie(mValue); }
     48 
     49 private:
     50  uint64_t mValue;
     51 };
     52 
     53 using APZScrollGeneration = ScrollGeneration<APZTag>;
     54 using MainThreadScrollGeneration = ScrollGeneration<MainThreadTag>;
     55 
     56 struct ScrollGenerationCounter {
     57  MainThreadScrollGeneration NewMainThreadGeneration() {
     58    uint64_t value = ++mCounter;
     59    return MainThreadScrollGeneration(value);
     60  }
     61 
     62  APZScrollGeneration NewAPZGeneration() {
     63    uint64_t value = ++mCounter;
     64    return APZScrollGeneration(value);
     65  }
     66 
     67 private:
     68  uint64_t mCounter = 0;
     69 };
     70 
     71 }  // namespace mozilla
     72 
     73 #endif  // mozilla_ScrollGeneration_h_