InputSystem基础框架

Key

flowchart LR

Input(PlayerController::UpdateInput)

Input
-->InputProcesssor::Tick
Input
-->InputHandle::Tick
Input
-->InputCollector::Tick

InputProcessor

对于 InputProcessor，进行按键的原始输入处理，调用 InputKey 将将数据传递到 InputCollector，继续后续的操作；

  1. 通过监听引擎原始的按键数据 APlayerController::IsInputKeyDown(const FKey Key)；
  2. 允许外部调用输入，执行 InputKey （比如某个 UI 点击触发输入）；

特别地，在 Tick 中进行原始数据处理；

由于一般按键输入支持 Ctrl / Shit / Alt / Cmd + Key，需要对这种情况适配，同时防止按键冲突：对于KeySetting(KeyType - 具体按键配置 映射) 额外维护 bCtrl (需要与 ctrl 组合)、MustNoCtrl (需要不按下 Ctrl)；

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// InputProcessor

void UInputProcessor::ProcessInputKey() // Tick
{
    bool bShift = PC->IsInputKeyDown(EKeys::LeftShift) || PC->IsInputKeyDown(EKeys::RightShift);
    bool bCtrl = PC->IsInputKeyDown(EKeys::LeftControl) || PC->IsInputKeyDown(EKeys::RightControl);
    bool bAlt = PC->IsInputKeyDown(EKeys::LeftAlt) || PC->IsInputKeyDown(EKeys::RightAlt);
    bool bCmd = PC->IsInputKeyDown(EKeys::LeftCommand) || PC->IsInputKeyDown(EKeys::RightCommand);
    
    auto IsKeyDown = [&](EInputKeyType KeyType) -> bool
    {
         for (auto KeySetting : KeySettings[KeyType]) // 一个 KeyType 可能有多种触发方式
        {
            bool bKeyDown = PC->IsInputKeyDown(FKey(FName(KeySetting.KeyName())));

            if ((KeySetting.Shift() && !bShift) || (KeySetting.MustNoShift() && bShift))
                bKeyDown = false;
            else if ((KeySetting.Ctrl() && !bCtrl) || (KeySetting.MustNoCtrl() && bCtrl))
                bKeyDown = false;
            else if ((KeySetting.Alt() && !bAlt) || (KeySetting.MustNoAlt() && bAlt))
                bKeyDown = false;
            else if ((KeySetting.Cmd() && !bCmd) || (KeySetting.MustNoCmd() && bCmd))
                bKeyDown = false;

            if (bKeyDown)
                return true;
        }
        
        return false;
    };

    for (auto KeyType : KeyTypes)
    {
        if (IsKeyDown(KeyType))
        {
            InputKey(KeyType);
        }
    }
}

// ----------

void UInputProcessor::InputKey(EInputKeyType KeyType)
{
    if (!IsValid(InputCollector)) return;
    InputCollector->SetKey(KeyType, true);
}

InputCollector

classDiagram
	direction LR
	
	InputCollector --> FInputKeyInfo
	class InputCollector {
		KeyInfoMap: TMap~KeyType, FInputKeyInfo~
	}
	
	FInputKeyInfo *-- EKeyState
	class FInputKeyInfo {
		bEnable : bool
		bPressed : bool
		KeyState : EKeyState
	}
	
	class EKeyState {
		IKS_Idle : 未按下
		IKS_Press : 当帧按下
		IKS_Release : 当帧释放
		IKS_Holding : 持续按下
	}

对于 InputCollector，维护 Key - Press 相关的原始输入数据，将数据从 Press 加工到 KeyState，并每帧检测是否未按下，这样外部只需要进行 Press，而不需要 Release；有几个主要的功能：

  1. 提供 SetKey 进行按键设置，提供 GetKey 查询按键状态；
  2. 维护每个 Key 的 KeyInfo，数据用于后续处理；
  3. 提供 EnableKey，设置按键是否可以输入（Disable 时需要取消输入）；
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// InputKeyInfo

USTRUCT(BlueprintType)
struct FInputKeyInfo
{
    GENERATED_BODY()

    UPROPERTY()
    bool bPressed = false;

    UPROPERTY()
    EInputKeyState KeyState = IKS_Idle;
    
    UPROPERTY()
    bool bEnable = true;

    // 用于记录该帧内是否已经处理过按键
    bool bProcessedThisFrame = false;
};
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// InputCollector

void UInputCollector::SetKey(EInputKeyType KeyType, bool bPressed, bool bForce)
{
    if (bForce || IsEnableKey(KeyType))
    {
        SetKey_Internal(KeyType, bPressed);
    }
}

FInputKeyInfo UInputCollector::GetKeyInfo(EInputKeyType KeyType)
{
    return KeyInfoMap.Contains(KeyType) ? KeyInfoMap[KeyType] : {};
}

// ----- Internal -----
void UInputCollector::Tick()
{
    // 每次 Tick 进行按键信息重置
    for (auto KeyType : KeyTypes)
    {
        FInputKeyInfo& KeyInfo = KeyInfoMap[KeyType];
        if (!KeyInfo.bProcessedThisFrame)
        {
            SetKey_Internal(KeyType, false);
           	KeyInfo.bProcessedThisFrame = false;
        }
    }
}   

void UInputCollector::SetKey_Internal(EInputKeyType KeyType, bool bPressed)
{
    FInputKeyInfo& KeyInfo = KeyInfoMap[KeyType];

    if (bPressed == KeyInfo.bPressed)
    {
        KeyInfo.KeyState = bPressed ? IKS_Holding : IKS_Idle;
    }
    else
    {
        KeyInfo.KeyState = bPressed ? IKS_Press : IKS_Release;
    }

    KeyInfo.bPressed = bPressed;
    KeyInfo.bProcessedThisFrame = true;
}

InputHandle

classDiagram
	class InputHandleBase {
		KeyInfo : TArray~EInputKeyType~
		
		SetInput(KeyType, bPressed)
		CollectInput()
		ProcessInput()
		NotifyInput()
	}
	
	InputHandleBase <|-- InputHandld_Default
	InputHandleBase <|-- InputHandle_Character
	InputHandleBase <|-- InputHandle_Vehicle

业务自定义逻辑的位置，一般仅对业务开放这部分的代码修改；

根据不同的输入模式，创建不同的 InputHandle，在这里对输入进行业务级别的加工，同时处理基本的输入操作回调（内部基本的业务逻辑，以及允许其它模块向内部注册的事件），并将输入操作通知给其它模块；

业务自定义其输入逻辑，比如：

  1. 该输入模式下，当输入某个操作时，系统自动取消其它操作的输入等；
  2. 处理按键是否需要自动抬起；
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// InputHandle

void UInputHandleBase::Tick()
{
    RecordInput();   // 记录上次输入结果
    CollectInput();  // 收集本帧输入结果（先默认清空，后根据具体情况收集）
    ProcessInput();  // 根据输入结果修改 KeyState
    DispatchInput(); // 分发输入结果并处理
}


// ----- Process -----

void UInputHandleBase::ProcessInput()
{
    for (auto Key : ActiveKeyTypes)
    {
        bool bLastKeyDown = RecordKeyInfoMap[Key].bPressed;
        bool bCurrentKeyDown = KeyInfoMap[Key].bPressed;
        
        if (bCurrentKeyDown != bLastKeyDown)
        {
            bCurrentKeyDown ? OnGameKeyPress(Key) : OnGameKeyRelease(Key);
        }
        else
        {
            bCurrentKeyDown ? OnGameKeyHolding(Key) : OnGameKeyIdle(Key);
        }
    }
}


// ----- Register -----

DECLARE_MULTICAST_DELEGATE_TwoParams(FInputEvent, KeyType, KeyState);
using FInputEventCallbackParamTypes = FInputEventCallbackType::FDelegate::TFuncType;

TMap <KeyType, FInputEvent> ProcessInputEvents;

template <
	typename UserClass,
	typename FuncType = TMemFunPtrType<TIsConst<UserClass>::Value, UserClass, FInputEventCallbackParamTypes>::Type
>
bool UInputHandleBase::RegisterInputEvent(EInputKeyType KeyType, UserClass* InUserObject, FuncType InFunc)
{
    if (!ProcessInputEvents.Contains(KeyType))
        ProcessInputEvents.Add(KeyType, {});

    auto& Event = Processvents[KeyType];
    if (Event.IsBoundToObject(InUserObject))
    {
        return false;
    }

    Event.AddUObject(InObject, InFunc);
    return true;
}

template <typename UserClass>
bool UnregisterInputEvent(EInputKeyType Type, UserClass* InUserObject)
{
    if (!ProcessInputEvents.Contains(Type))
        return false;

    auto& Event = ProcessInputEvents[Type];
    Event.RemoveAll(InUserObject);
    return true;
}
                                
void UInputHandleBase::DispatchInput()
{
    // 内部处理基础操作
    // ...
        
    // 执行外部注册的操作
    for (auto KeyType : ActiveKeyTypes)
    {
        if (auto EventPtr = ProcessInputEvents.Find(KeyType))
        {
            EventPtr->Broadcast(KeyType, GetKeyState(KeyType));
        }
    }
}

// ----- Helper -----

void UInputHandleBase::SetInput(EKeyType KeyType)
{
    KeyInfo[KeyType].bPressed = true;
}

void UInputHandleBase::UpdateKeyFromCollector(EInputKeyType KeyType) // 在 CollectInput 中调用
{
    SetInput(KeyType, InputCollector->GetKeyInfo(KeyType).bPressed);
}

Mouse

InputProcessor

Interface : IInputProcessor 由 FSlateApplication 驱动，也有 Key、Mouse 相关操作的回调：

flowchart LR

FSlateApplication::ProcessMouseButtonDownEvent
-->FSlateApplication::InputPreProcessorsHelper::HandleMouseButtonDownEvent
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// IInputProcessor

class SLATE_API IInputProcessor
{
public:
	IInputProcessor(){};
	virtual ~IInputProcessor(){}

	virtual void Tick(const float DeltaTime, FSlateApplication& SlateApp, TSharedRef<ICursor> Cursor) = 0;

    // Key...
	virtual bool HandleKeyDownEvent(FSlateApplication& SlateApp, const FKeyEvent& InKeyEvent) { return false; }
	virtual bool HandleKeyUpEvent(FSlateApplication& SlateApp, const FKeyEvent& InKeyEvent) { return false; }
	virtual bool HandleAnalogInputEvent(FSlateApplication& SlateApp, const FAnalogInputEvent& InAnalogInputEvent) { return false; }

    // Mouse...
	virtual bool HandleMouseMoveEvent(FSlateApplication& SlateApp, const FPointerEvent& MouseEvent) { return false; }
	virtual bool HandleMouseButtonDownEvent( FSlateApplication& SlateApp, const FPointerEvent& MouseEvent) { return false; }
	virtual bool HandleMouseButtonUpEvent( FSlateApplication& SlateApp, const FPointerEvent& MouseEvent) { return false; }
	virtual bool HandleMouseButtonDoubleClickEvent(FSlateApplication& SlateApp, const FPointerEvent& MouseEvent) { return false; }
	virtual bool HandleMouseWheelOrGestureEvent(FSlateApplication& SlateApp, const FPointerEvent& InWheelEvent, const FPointerEvent* InGestureEvent) { return false; }
	virtual bool HandleMotionDetectedEvent(FSlateApplication& SlateApp, const FMotionEvent& MotionEvent) { return false; };

	/** Debug name for logging purposes */
	virtual const TCHAR* GetDebugName() const { return TEXT(""); }
};

可以在合适的地方（比如 InputSubSystem / InputManager ）进行创建：

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InputProcessor = MakeShareable(new FInputProcessor());
FSlateApplication::Get().RegisterInputPreProcessor(InputProcessor);

其次是与 UI 的交互， UserWidget 中也提供了 Mouse 的回调：

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virtual FReply NativeOnTouchStarted(const FGeometry& InGeometry, const FPointerEvent& InGestureEvent) override;
virtual FReply NativeOnTouchMoved(const FGeometry& InGeometry, const FPointerEvent& InGestureEvent) override;
virtual FReply NativeOnTouchEnded(const FGeometry& InGeometry, const FPointerEvent& InGestureEvent) override;
virtual FReply NativeOnMouseWheel(const FGeometry& InGeometry, const FPointerEvent& InMouseEvent) override;

可以将接口收束在一个 InputManager 中，向外暴露相关事件；

DragDrop

DragArea 用于维护可拖动的范围，以及封装引擎基本接口、提供注册方法：

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-- DragArea

--region ----- Events -----

function DragAreaView:OnMouseButtonDown(Geometry, MouseEvent)
	return UE.UWidgetBlueprintLibrary.DetectDragIfPressed(MouseEvent, self, "LeftMouseButton")
end

-- 开始拖动
function DragAreaView:OnDragDetected(Geometry, PointerEvent)
	local OperationClass = self.DragDropOperationClass
	local Operation = NewObject(OperationClass)

	if self.DragDetectedDelegate ~= nil then
		for Object, Callback in pairs(self.DragDetectedDelegate) do
			xpcall(Callback, error_handler, Object, Geometry, PointerEvent, Operation)
		end
	end
	
	return Operation
end

-- 取消拖动
function DragAreaView:OnDragCancelled(Geometry, PointerEvent, Operation)
	if self.DragCancelledDelegate ~= nil then
		for Object, Callback in pairs(self.DragCancelledDelegate) do
			xpcall(Event, error_handler, Object, Geometry, PointerEvent, Operation)
		end
	end
end

-- Other...

--endregion Events

--reigon ----- Bind -----
function DragAreaView:BindEvent(EventName, Object, Callback)
    if self[EventName] == nil then self[EventName] = {} end

    if self[EventName][Object] == nil then
        self[EventName][Object] = Callback
    end
end

function DragAreaView:UnbindEvent(EventName, Object)
    if self[EventName] == nil then self[EventName] = {} end

    if self[EventName][Object] ~= nil then
        self[EventName][Object] = nil
    end
end

function DragAreaView:BindDragDetected(Object,Func) self:BindEvent("DragDetectedDelegate", Object, Func) end
function DragAreaView:UnbindDragDetected(Object) self:UnbindEvent("DragDetectedDelegate", Object) end

function DragAreaView:BindDragCancelled(Object,Func) self:BindEvent("DragCancelledDelegate", Object, Func) end
function DragAreaView:UnbindDragCancelled(Object) self:UnbindEvent("DragCancelledDelegate", Object) end

--endregion Bind

DragItem 用于维护拖动的实际 Item；

PreviewItem 用于维护拖动时的 Preview（也就是拖动时显示的 Item 预览）；

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-- DragItem

function DragItemView:Construct()
	self.DragArea:BindDragDetected(self, self.OnDragDetectedCallback)
	self.DragArea:BindDragCancelled(self, self.OnDragCancelledCallback)
end

function DragItemView:Destruct()
	self.DragArea:UnbindDragDetected(self)
	self.DragArea:UnbindDragCancelled(self)
end

--
function DragItemView:OnDragDetectedCallback(Geometry,PointerEvent,Operation)

	local BPClass = UE.UGameplayStatics.GetObjectClass(self)
	Operation.PreviewItem = UE.UCommonWidgetUtils.CreateWidget(BPClass)

	Operation.DefaultDragVisual = Operation.PreviewItem
	if Operation.PreviewItem and Operation.PreviewItem.OnDragDetected then
		Operation.PreviewItem:OnDragDetected()
	end

	Operation.Pivot = UE.EDragPivot.TopLeft

	local LocalPosition = UE.USlateBlueprintLibrary.AbsoluteToLocal(self:GetCachedGeometry(), UE.UKismetInputLibrary.PointerEvent_GetScreenSpacePosition(PointerEvent))

	local Offset = UE.FVector2D()
	local Size = UE.USlateBlueprintLibrary.GetLocalSize(self:GetCachedGeometry())
	Offset.X = LocalPosition.X / Size.X * -1
	Offset.Y = LocalPosition.Y / Size.Y * -1
	Operation.Offset = Offset

	Operation.UseInAnimation = false
end

function DragItemView:OnDragCancelledCallback(Geometry, PointerEvent, Operation)

	if Operation.PreviewItem and Operation.PreviewItem.OnDragCancelled then
		Operation.PreviewItem:OnDragCancelled()
	end

	UE.UCommonWidgetUtils.DestroyWidget(Operation.PreviewItem)
end

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// CommonWidgetUtils

UUserWidget* UCommonWidgetUtils::CreateWidget(UWorld* InWorld, TSubclassOf<UUserWidget> WidgetType)
{
	UUserWidget* Widget = UWidgetBlueprintLibrary::Create(InWorld, WidgetType, nullptr);
	AddObjectRef(Widget);
	return Widget;
}

void UCommonWidgetUtils::DestroyWidget(UUserWidget* Widget)
{
	RemoveObjectRef(Widget);
}

// --------------

void UCommonWidgetUtils::AddObjectRef(UObject* Object)
{
	if (Object && IsUObjectValid(Object))
	{
		const auto L = UnLua::GetState();
		auto& Env = UnLua::FLuaEnv::FindEnvChecked(L);
		Env.AddManualObjectReference(Object);
	}
}

void UCommonWidgetUtils::RemoveObjectRef(UObject* Object)
{
	if (Object && IsUObjectValid(Object))
	{
		const auto L = UnLua::GetState();
		auto& Env = UnLua::FLuaEnv::FindEnvChecked(L);
		Env.RemoveManualObjectReference(Object);
	}
}

特别地：

  1. 通过 Operation 的 DefaultDragVisual 来设置拖动时的预览 Widget，在 FUMGDragDropOp::New 时，将其设置到 Operation->DecoratorWidget，并在 FUMGDragDropOp::OnDragged 时更新 Position；
  2. CreateWidget / DestroyWidget 针对 PreviewItem，这里可以额外维护一个 Pool 进行 Widget 复用；
  3. 在合适的地方增加额外 Callback；

Touch

引擎对于 Touch 的相关实现主要在：UPlayerInput::InputTouch(uint32 Handle, ETouchType::Type Type, const FVector2D& TouchLocation, float Force, FDateTime DeviceTimestamp, uint32 TouchpadIndex) 中；

实际上，可以根据 IInputProcessor 提供的接口，在 InputManager 中维护 TArray <FInputTouchData> InputTouchDatas 以及相关信息，统一管理并分发给各个业务模块，同时方便自定义与扩展。

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// InputTouchData
struct FInputTouchData
{
	ETouchIndex::Type TouchIndex;
	FVector2D StartLocation;
	FVector2D Location;
	FVector2D DeltaMove;
	float BeginTime;
	float UpdateTime;
	float DeltaTime;
	float ForceValue;
	bool bPendingKill;
    
    // ....
}

需要和引擎一样维护所有的 TouchData，这样才可以通过 TouchIndex 与其它的接口关联，对应到其它回调的 PointerEvent 中的 (ETouchIndex::Type)PointerEvent.GetPointerIndex()；

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// InputProcessor

class FInputProcessor
{
    // ...
    TArray <FInputTouchData> InputTouchDatas;
}
    
FInputTouchData FInputProcessor::GetInputTouchData(ETouchIndex::Type TouchIndex)
{
    FInputTouchData* DataPtr = InputTouchDatas.FindByKey(TouchIndex);
    return DataPtr != nullptr ? *DataPtr : {};
}

// ----- Process -----

void FInputProcessor::ProcessMouseEvent(ETouchType TouchType, const FPointerEvent& MouseEvent)
{
    FVector2D OutPixelPosition = FVector2D::ZeroVector;
    FVector2D OutViewportPosition = FVector2D::ZeroVector;
    USlateBlueprintLibrary::AbsoluteToViewport(GetWorld(), MouseEvent.GetScreenSpacePosition(), OutPixelPosition, OutViewportPosition);

    InputTouch(MouseEvent.GetPointerIndex(), TouchType, OutPixelPosition, MouseEvent.GetTouchForce());
}

bool FInputProcessor::HandleMouseButtonDownEvent(FSlateApplication& SlateApp, const FPointerEvent& MouseEvent)
{
    ProcessMouseEvent(ETouchType::Began, MouseEvent);
    // BrodcastEvents..
    return true;
}

bool FInputProcessor::HandleMouseMoveEvent(FSlateApplication& SlateApp, const FPointerEvent& MouseEvent)
{
    ProcessMouseEvent(ETouchType::Moved, MouseEvent);
    // BrodcastEvents..
    return true;
}

bool FInputProcessor::HandleMouseButtonUpEvent(FSlateApplication& SlateApp, const FPointerEvent& MouseEvent)
{
    ProcessMouseEvent(ETouchType::Ended, MouseEvent);
    // BrodcastEvents..
    
    // Clear PendingKill Datas
    for (int Index = InputTouchDatas.Num() - 1; Index >= 0; Index--)
    {
        if (InputTouchDatas[Index].bPendingKill == true)
        {
            InputTouchDatas.RemoveAt(Index);
        }
    }
    return true;
}

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// InputProcessor

void FInputProcessor::InputTouch(uint32 Handle, ETouchType::Type Type, const FVector2D& TouchLocation, float Force)
{
    FVector Location(TouchLocation, Force);

    switch (Type)
    {
    case ETouchType::Began:
        BeginTouch((ETouchIndex::Type)Handle, Location);
        break;
    case ETouchType::Ended:
        EndTouch((ETouchIndex::Type)Handle, Location);
        break;
    default:
        MoveTouch((ETouchIndex::Type)Handle, Location);
        break;
    }
}

// -----
void FInputProcessor::BeginTouch(const ETouchIndex::Type TouchIndex, const FVector Location)
{
    FInputTouchData* DataPtr = InputTouchDatas.FindByKey(TouchIndex);
    if (DataPtr == nullptr)
    {
        InputTouchDatas.AddDefaulted(1);
        DataPtr = &InputTouchDatas.Last();
    }
    
    FInputTouchData& InputTouchData = *DataPtr;
    InputTouchData.TouchIndex = TouchIndex;
    InputTouchData.StartLocation = InputTouchData.Location = FVector2D(Location.X, Location.Y);
    InputTouchData.ForceValue = Location.Z;
    InputTouchData.BeginTime = InputTouchData.UpdateTime = GetWorld()->GetTimeSeconds();
}

void FInputProcessor::MoveTouch(const ETouchIndex::Type TouchIndex, const FVector Location)
{
    FInputTouchData* DataPtr = InputTouchDatas.FindByKey(TouchIndex);
    if (DataPtr == nullptr) return;

    FInputTouchData& InputTouchData = *DataPtr;
    FVector2D ScreenLocation = FVector2D(Location.X, Location.Y);
    InputTouchData.DeltaMove = ScreenLocation - InputTouchData.Location;
    InputTouchData.Location = ScreenLocation;
    InputTouchData.ForceValue = Location.Z;
    InputTouchData.DeltaTime = GetWorld()->GetDeltaSeconds();
    InputTouchData.UpdateTime = GetWorld()->GetTimeSeconds();
}

void FInputProcessor::EndTouch(const ETouchIndex::Type TouchIndex, const FVector Location)
{
    for (auto& InputTouchData : InputTouchDatas)
    {
        if (InputTouchData.TouchIndex == TouchIndex)
        {
            InputTouchData.bPendingKill = true;
        }
    }
}

这样就在 InputProcessor 中维护了所有的 TouchDatas，可以分发事件给外部监听，以及提供数据查询。

Gesture

根据 Touch 的信息，通过 FGestureRecognizer 维护 Gesture_Pinch、Gesture_Flick、Gesture_Rotate 等；

在 UPlayerInput::Tick 中会进行 GestureRecognizer.DetectGestures(Touches, this, DeltaTime) ：

  1. 对于 Pinch：如果 float* CurrentAlpha = CurrentGestureValues.Find(EKeys::Gesture_Pinch) 即 Pinch 还未开启，并且本次 TouchCount > 2，则认为 Pinch 刚刚开始，此时根据 CurrentPinchPoint_Start、CurrentPinchPoint_End 计算出 AnchorDistanceSq 并存储，将 1.0f 作为基础缩放值存储在 GestureValue；在下一次根据新的 NewDistanceSq / AnchorDistanceSq 作为缩放值记录在 CurrentGestureValues[EKeys::Gesture_Pinch]； TouchCount 减少到 < 2 时， Pinch 结束；
  2. 对于 Flick：要求 FlickTime < 0.25f && (FlickCurrent - AnchorPoints[0]).SizeSquared() > 10000.f，经过的时间在 0.25s 内，并且滑动一定的距离；计算和存储 Angle 于 CurrentGestureValues[EKeys::Gesture_Flick]；
  3. 对于 Rotate：如果 float* CurrentAngle = CurrentGestureValues.Find(EKeys::Gesture_Rotate) 即 Rotate 还未开启，当 TouchCount > 2 时，则认为 Rotate 刚刚开始，此时计算出 StartAngle 记录，将 0.0f 作为基础旋转值存储在 GestureValue；在后续更新 GestureValue 为 NewAngle - StartAngle，表示相对角度； TouchCount 减少到 < 2 时， Rotate 结束；

最后：

Gesture CurrentGestureValue : Type
Pinch Scale （相对开始的比例缩放）
Flick Angle（本次滑动的角度）
Rotate Angle （相对开始的角度） 
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bool UPlayerInput::InputGesture(const FKey Gesture, const EInputEvent Event, const float Value)
{
	FKeyState& KeyState = KeyStateMap.FindOrAdd(Gesture);

	KeyState.Value.X = KeyState.RawValue.X = KeyState.RawValueAccumulator.X = Value;
	KeyState.EventAccumulator[Event].Add(++EventCount);

	return true;
}

这些信息会存储在 KeyState 里，通过 UPlayerInput::GetKeyState(FKey InKey) 获取；

当然，在 Mouse 的回调中：

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virtual FReply NativeOnTouchStarted(const FGeometry& InGeometry, const FPointerEvent& InGestureEvent) override;
virtual FReply NativeOnTouchMoved(const FGeometry& InGeometry, const FPointerEvent& InGestureEvent) override;
virtual FReply NativeOnTouchEnded(const FGeometry& InGeometry, const FPointerEvent& InGestureEvent) override;

可以看到这里有 GestureEvent，也可以获取对应主要信息：

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FVector2D ScreenSpacePosition;
FVector2D LastScreenSpacePosition;
FVector2D CursorDelta;
const TSet<FKey>* PressedButtons;
FKey EffectingButton;
uint32 PointerIndex;
uint32 TouchpadIndex;
float Force;
bool bIsTouchEvent;
EGestureEvent GestureType;
FVector2D WheelOrGestureDelta;
bool bIsDirectionInvertedFromDevice;
bool bIsTouchForceChanged;
bool bIsTouchFirstMove;

实际上，可以将这里的 GestureRecognizer 移到统一维护的 InputManager 中，将相关信息提供给各个业务查询，方便自定义与扩展：比如增加 Tag 限定提供给外部设置，当且仅当 Tag 一致时，进行对应 Gesture 更新等。

参考

UE 5.4 源码