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CoalescedInputData.h (2977B)

      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 mozilla_dom_CoalescedInputData_h
      8 #define mozilla_dom_CoalescedInputData_h
      9 
     10 #include "mozilla/UniquePtr.h"
     11 #include "mozilla/layers/ScrollableLayerGuid.h"
     12 #include "nsRefreshObservers.h"
     13 
     14 class nsRefreshDriver;
     15 
     16 namespace mozilla::dom {
     17 
     18 class BrowserChild;
     19 
     20 template <class InputEventType>
     21 class CoalescedInputData {
     22 protected:
     23  using ScrollableLayerGuid = mozilla::layers::ScrollableLayerGuid;
     24 
     25  UniquePtr<InputEventType> mCoalescedInputEvent;
     26  ScrollableLayerGuid mGuid;
     27  uint64_t mInputBlockId = 0;
     28  uint32_t mGeneration = 0;
     29 
     30  void AdvanceGeneration() {
     31    if (!IsEmpty()) {
     32      mGeneration++;
     33    }
     34  }
     35 
     36 public:
     37  CoalescedInputData() = default;
     38 
     39  void RetrieveDataFrom(CoalescedInputData& aSource) {
     40    aSource.AdvanceGeneration();
     41    AdvanceGeneration();
     42    mCoalescedInputEvent = std::move(aSource.mCoalescedInputEvent);
     43    mGuid = aSource.mGuid;
     44    mInputBlockId = aSource.mInputBlockId;
     45  }
     46 
     47  bool IsEmpty() { return !mCoalescedInputEvent; }
     48 
     49  bool CanCoalesce(const InputEventType& aEvent,
     50                   const ScrollableLayerGuid& aGuid,
     51                   const uint64_t& aInputBlockId);
     52 
     53  UniquePtr<InputEventType> TakeCoalescedEvent() {
     54    AdvanceGeneration();
     55    return std::move(mCoalescedInputEvent);
     56  }
     57 
     58  ScrollableLayerGuid GetScrollableLayerGuid() { return mGuid; }
     59 
     60  uint64_t GetInputBlockId() { return mInputBlockId; }
     61 
     62  /**
     63   * The generation number of the latest state stored by the instance.
     64   * It'll be incremented when the coalesced event data is retrieved or taken.
     65   * So, this is useful to avoid handling same coalesced events twice when
     66   * a nested event loop may handle this.
     67   * NOTE: You should compare the value only with `==` or `!=`.  Do not use
     68   * `<` nor `>` because the value may circulate to 0 from UINT32_MAX.
     69   */
     70  [[nodiscard]] uint32_t Generation() const { return mGeneration; }
     71 };
     72 
     73 class CoalescedInputFlusher : public nsARefreshObserver {
     74 public:
     75  explicit CoalescedInputFlusher(BrowserChild* aBrowserChild);
     76 
     77  virtual void WillRefresh(mozilla::TimeStamp aTime) override = 0;
     78 
     79  NS_INLINE_DECL_REFCOUNTING(CoalescedInputFlusher, override)
     80 
     81  void StartObserver();
     82  void RemoveObserver();
     83 
     84  /**
     85   * Return a refresh driver which is proper one for BrowserChild.
     86   * Note that this is not a getter of mRefreshDriver.
     87   */
     88  [[nodiscard]] nsRefreshDriver* GetRefreshDriver();
     89 
     90 protected:
     91  virtual ~CoalescedInputFlusher();
     92 
     93  BrowserChild* mBrowserChild;
     94  // A refresh driver which this instance waits for the next refresh of.
     95  RefPtr<nsRefreshDriver> mRefreshDriver;
     96 };
     97 }  // namespace mozilla::dom
     98 
     99 #endif  // mozilla_dom_CoalescedInputData_h