WheelBlockState*
InputQueue::GetActiveWheelTransaction() const
{
  WheelBlockState* block = mActiveWheelBlock.get();
  if (!block || !block->InTransaction()) {
    return nullptr;
  }
  return block;
}
WheelBlockState*
InputQueue::GetCurrentWheelTransaction() const
{
  if (mInputBlockQueue.IsEmpty()) {
    return nullptr;
  }
  WheelBlockState* block = CurrentBlock()->AsWheelBlock();
  if (!block || !block->InTransaction()) {
    return nullptr;
  }
  return block;
}
nsEventStatus
InputQueue::ReceiveScrollWheelInput(const RefPtr<AsyncPanZoomController>& aTarget,
                                    bool aTargetConfirmed,
                                    const ScrollWheelInput& aEvent,
                                    uint64_t* aOutInputBlockId) {
  WheelBlockState* block = nullptr;
  if (!mInputBlockQueue.IsEmpty()) {
    block = mInputBlockQueue.LastElement()->AsWheelBlock();

    // If the block is not accepting new events we'll create a new input block
    // (and therefore a new wheel transaction).
    if (block &&
        (!block->ShouldAcceptNewEvent() ||
         block->MaybeTimeout(aEvent)))
    {
      block = nullptr;
    }
  }

  MOZ_ASSERT(!block || block->InTransaction());

  if (!block) {
    block = new WheelBlockState(aTarget, aTargetConfirmed, aEvent);
    INPQ_LOG("started new scroll wheel block %p for target %p\n", block, aTarget.get());

    SweepDepletedBlocks();
    mInputBlockQueue.AppendElement(block);

    CancelAnimationsForNewBlock(block);
    MaybeRequestContentResponse(aTarget, block);
  } else {
    INPQ_LOG("received new event in block %p\n", block);
  }

  if (aOutInputBlockId) {
    *aOutInputBlockId = block->GetBlockId();
  }

  block->Update(aEvent);

  // Note that the |aTarget| the APZCTM sent us may contradict the confirmed
  // target set on the block. In this case the confirmed target (which may be
  // null) should take priority. This is equivalent to just always using the
  // target (confirmed or not) from the block, which is what
  // MaybeHandleCurrentBlock() does.
  if (!MaybeHandleCurrentBlock(block, aEvent)) {
    block->AddEvent(aEvent.AsScrollWheelInput());
  }

  return nsEventStatus_eConsumeDoDefault;
}
nsEventStatus
InputQueue::ReceiveScrollWheelInput(const RefPtr<AsyncPanZoomController>& aTarget,
                                    bool aTargetConfirmed,
                                    const ScrollWheelInput& aEvent,
                                    uint64_t* aOutInputBlockId) {
  WheelBlockState* block = mActiveWheelBlock.get();
  // If the block is not accepting new events we'll create a new input block
  // (and therefore a new wheel transaction).
  if (block &&
      (!block->ShouldAcceptNewEvent() ||
       block->MaybeTimeout(aEvent)))
  {
    block = nullptr;
  }

  MOZ_ASSERT(!block || block->InTransaction());

  if (!block) {
    block = new WheelBlockState(aTarget, aTargetConfirmed, aEvent);
    INPQ_LOG("started new scroll wheel block %p id %" PRIu64 " for target %p\n",
        block, block->GetBlockId(), aTarget.get());

    mActiveWheelBlock = block;

    CancelAnimationsForNewBlock(block);
    MaybeRequestContentResponse(aTarget, block);
  } else {
    INPQ_LOG("received new event in block %p\n", block);
  }

  if (aOutInputBlockId) {
    *aOutInputBlockId = block->GetBlockId();
  }

  // Note that the |aTarget| the APZCTM sent us may contradict the confirmed
  // target set on the block. In this case the confirmed target (which may be
  // null) should take priority. This is equivalent to just always using the
  // target (confirmed or not) from the block, which is what
  // ProcessQueue() does.
  mQueuedInputs.AppendElement(MakeUnique<QueuedInput>(aEvent, *block));

  // The WheelBlockState needs to affix a counter to the event before we process
  // it. Note that the counter is affixed to the copy in the queue rather than
  // |aEvent|.
  block->Update(mQueuedInputs.LastElement()->Input()->AsScrollWheelInput());

  ProcessQueue();

  return nsEventStatus_eConsumeDoDefault;
}