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  3. FStateTreeExecutionContext

FStateTreeExecutionContext

StateTree Execution Context is a helper that is used to update StateTree instance data.

API > API/Plugins > API/Plugins/StateTreeModule

Inheritance Hierarchy

References

   
Module StateTreeModule
Header /Engine/Plugins/Runtime/StateTree/Source/StateTreeModule/Public/StateTreeExecutionContext.h
Include #include "StateTreeExecutionContext.h"

Syntax

struct FStateTreeExecutionContext

Remarks

StateTree Execution Context is a helper that is used to update StateTree instance data.

The context is meant to be temporary, you should not store a context across multiple frames.

The owner is used as the owner of the instantiated UObjects in the instance data and logging, it should have same or greater lifetime as the InstanceData.

In common case you can use the constructor to initialize the context, and us a helper struct to set up the context data and external data getter: FStateTreeExecutionContext Context(*GetOwner(), *StateTreeRef.GetStateTree(), InstanceData); if (SetContextRequirements(Context)) { Context.Tick(DeltaTime); }

bool UMyComponent::SetContextRequirements(FStateTreeExecutionContext& Context) { if (!Context.IsValid()) { return false; } // Setup context data Context.SetContextDataByName(...); ...

Context.SetCollectExternalDataCallback(FOnCollectStateTreeExternalData::CreateUObject(this, &UMyComponent::CollectExternalData);

return Context.AreContextDataViewsValid(); }

bool UMyComponent::CollectExternalData(const FStateTreeExecutionContext& Context, const UStateTree* StateTree, TArrayView ExternalDataDescs, TArrayView OutDataViews) { ... for (int32 Index = 0; Index < ExternalDataDescs.Num(); Index++) { const FStateTreeExternalDataDesc& Desc = ExternalDataDescs[Index]; if (Desc.Struct->IsChildOf(UWorldSubsystem::StaticClass())) { UWorldSubsystem* Subsystem = World->GetSubsystemBase(Cast(const_cast(Desc.Struct.Get()))); OutDataViews[Index] = FStateTreeDataView(Subsystem); } ... } return true; }

In this example the SetContextRequirements() method is used to set the context defined in the schema, and the delegate FOnCollectStateTreeExternalData is used to query the external data required by the tasks and conditions.

In case the State Tree links to other state tree assets, the collect external data might get called multiple times, once for each asset.

Variables

  Type Name Description
Protected variable bool bActiveExternalDataCollected  
Protected variable bool bAllowDirectTransitions True if transitions are allowed to be requested directly instead of buffering.
Protected variable bool bRecordTransitions If true, the state tree context will create snapshots of transition events and capture them within RecordedTransitions for later use.
Protected variable TArray< FCollectedExternalDataCache, TConcurrentLinearArrayAllocator< FDefaultBlockAllocationTag > > CollectedExternalCache  
Protected variable FOnCollectStateTreeExternalData CollectExternalDataDelegate  
Protected variable TArray< FStateTreeDataView, TConcurrentLinearArrayAllocator< FDefaultBlockAllocationTag > > ContextAndExternalDataViews Data view of the context data.
Protected variable const FStateTreeExecutionFrame * CurrentlyProcessedFrame  
Protected variable const FStateTreeExecutionFrame * CurrentlyProcessedParentFrame Current frame we're processing.
Protected variable FStateTreeInstanceStorage * CurrentlyProcessedSharedInstanceStorage Pointer to the shared instance data of the current frame we're processing.
Protected variable FStateTreeStateHandle CurrentlyProcessedState Current state we're processing, or invalid if not applicable.
Protected variable FStateTreeFrameStateSelectionEvents * CurrentlyProcessedStateSelectionEvents Current frames events we're processing during the state selection, or invalid if not applicable.
Protected variable const FStateTreeEvent * CurrentlyProcessedTransitionEvent Current event we're processing in transition, or invalid if not applicable.
Protected variable FStateTreeDataHandle CurrentNodeDataHandle Currently processed nodes instance data.
Protected variable FStateTreeDataView CurrentNodeInstanceData  
Protected variable TSharedPtr< FStateTreeEventQueue > EventQueue Events queue to use, cached for less indirections.
Protected variable FStateTreeInstanceData & InstanceData Instance data used during current tick.
Protected variable FStateTreeInstanceStorage * InstanceDataStorage Data storage of the instance data, cached for less indirections.
Protected variable const FStateTreeReferenceOverrides * LinkedStateTreeOverrides Pointer to linked state tree overrides.
Protected variable FStateTreeTransitionResult NextTransition Next transition, used by RequestTransition().
Protected variable FStateTreeTransitionSource NextTransitionSource Structure describing the origin of the state transition that caused the state change.
Protected variable UObject & Owner Owner of the instance data.
Protected variable TArray< FRecordedStateTreeTransitionResult > RecordedTransitions Captured snapshots for transition results that can be used to recreate transitions.
Protected variable const UStateTree & RootStateTree The StateTree asset the context is initialized for

Constructors

  Type Name Description
Public function  

FStateTreeExecutionContext ( const FStateTreeExecutionContext& InContextToCopy,
const UStateTree& InStateTree,
FStateTreeInstanceData& InInstanceData
)

 Construct an execution context from a parent context and another tree.
Public function  

FStateTreeExecutionContext ( UObject& InOwner,
const UStateTree& InStateTree,
FStateTreeInstanceData& InInstanceData,
const FOnCollectStateTreeExternalData& CollectExternalDataCallback,
const EStateTreeRecordTransitions RecordTransitions
)

  

Destructors

  Type Name Description
Public function Virtual    

Functions

  Type Name Description
Protected function FStateTreeDataView

AddTemporaryInstance ( const FStateTreeExecutionFrame& Frame,
const FStateTreeIndex16 OwnerNodeIndex,
const FStateTreeDataHandle DataHandle,
FConstStructView NewInstanceData
)

 Adds a temporary instance that can be located using frame and data handle later.
Public function Const bool  
Public function Const bool  
Protected function Virtual void Callback when delayed transition is triggered.
Protected function void

CallStopOnEvaluatorsAndGlobalTasks ( const FStateTreeExecutionFrame* ParentFrame,
const FStateTreeExecutionFrame& Frame,
const FStateTreeTransitionResult& Transition,
const FStateTreeIndex16 LastInitializedTaskIndex
)

 Stops evaluators and global tasks of the given frame. Expects nodes data to be already bound.
Protected function void

CaptureNewStateEvents ( TConstArrayView< FStateTreeExecutionFrame > PrevFrames,
TConstArrayView< FStateTreeExecutionFrame > NewFrames,
TArrayView< FStateTreeFrameStateSelectionEvents > FramesStateSelectionEvents
)

 Captures StateTree events used during the state selection.
Protected function bool Collects external data for all StateTrees in active frames.
Protected function FStateTreeIndex16

CollectExternalData ( const UStateTree* StateTree
)

 Collects external data for specific State Tree asset.
Public function void Consumes and removes the specified event from the event queue.
Protected function bool

CopyBatchOnActiveInstances ( const FStateTreeExecutionFrame* ParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeDataView TargetView,
const FStateTreeIndex16 BindingsBatch
)

 Copies a batch of properties to the data in TargetView.
Protected function bool

CopyBatchWithValidation ( const FStateTreeExecutionFrame* ParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeDataView TargetView,
const FStateTreeIndex16 BindingsBatch
)

 Copies a batch of properties to the data in TargetView.
Protected function Const FString  
Protected function Const FString

DebugGetStatePath ( TConstArrayView< FStateTreeExecutionFrame > ActiveFrames,
const FStateTreeExecutionFrame* CurrentFrame,
const int32 ActiveStateIndex
)

  
Public function void  
Protected function EStateTreeRunStatus Handles logic for entering State.
Protected function void

EvaluatePropertyFunctionsOnActiveInstances ( const FStateTreeExecutionFrame* CurrentParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
FStateTreeIndex16 FuncsBegin,
uint16 FuncsNum
)

 Evaluate all function at given range.
Protected function void

EvaluatePropertyFunctionsWithValidation ( const FStateTreeExecutionFrame* CurrentParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
FStateTreeIndex16 FuncsBegin,
uint16 FuncsNum
)

 Evaluate all function at given range.
Protected function float

EvaluateUtility ( const FStateTreeExecutionFrame* CurrentParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
const int32 ConsiderationsOffset,
const int32 ConsiderationsNum,
const float StateWeight
)

 Calculate the final score of all considerations at given range
Protected function void

ExitState ( const FStateTreeTransitionResult& Transition
)

 Handles logic for exiting State.
Public function Static const FStateTreeExecutionFrame *

FindFrame ( const UStateTree* StateTree,
FStateTreeStateHandle RootState,
TConstArrayView< FStateTreeExecutionFrame > Frames,
const FStateTreeExecutionFrame*& OutParentFrame
)

 Looks for a frame in provided list of frames.
Public function EStateTreeRunStatus Forces transition to a state from a previously recorded state tree transition result.
Public function Const TEnableIf< TIsInvocable< TFunc, FStateTreeEvent >::Value, void >::Type

ForEachEvent ( TFunc&& Function
)

 Iterates over all events.
Public function Const TEnableIf< TIsInvocable< TFunc, FStateTreeSharedEvent >::Value, void >::Type

ForEachEvent ( TFunc&& Function
)

 Iterates over all events.
Public function Const TConstArrayView< FStateTreeExecutionFrame >  
Public function Const FString  
Public function Const TArray< FName >  
Public function Const const FStateTreeActiveStates &  
Public function Const TConstArrayView< FStateTreeExternalDataDesc >  
Public function Const const FStateTreeExecutionFrame *  
Public function Const const FStateTreeExecutionFrame *  
Public function Const FStateTreeStateHandle  
Protected function FStateTreeDataView

GetDataView ( const FStateTreeExecutionFrame* ParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeDataHandle Handle
)

  
Public function Static FStateTreeDataView

GetDataView ( FStateTreeInstanceStorage& InstanceDataStorage,
FStateTreeInstanceStorage* CurrentlyProcessedSharedInstanceStorage,
const FStateTreeExecutionFrame* ParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
TConstArrayView< FStateTreeDataView > ContextAndExternalDataViews,
const FStateTreeDataHandle Handle
)

  
Public function Static FStateTreeDataView

GetDataViewFromInstanceStorage ( FStateTreeInstanceStorage& InstanceDataStorage,
FStateTreeInstanceStorage* CurrentlyProcessedSharedInstanceStorage,
const FStateTreeExecutionFrame* ParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeDataHandle Handle
)

  
Protected function FStateTreeDataView

GetDataViewOrTemporary ( const FStateTreeExecutionFrame* ParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeDataHandle Handle
)

  
Public function Const const FStateTreeEventQueue &  
Public function Const TConstArrayView< FStateTreeEvent >  
Public function Const TConstArrayView< FStateTreeSharedEvent >  
Protected function FStateTreeExecutionState &  
Protected function Const const FStateTreeExecutionState &  
Public function Const T::DataType &

GetExternalData ( const T Handle
)

 Returns reference to external data based on provided handle.
Public function Const TConstArrayView< FStateTreeExternalDataDesc >  
Public function Const FStateTreeExternalDataHandle

GetExternalDataHandleByStruct ( const UStruct* InStruct
)

  
Public function Const T::DataType *

GetExternalDataPtr ( const T Handle
)

 Returns pointer to external data based on provided item handle.
Public function FStateTreeDataView  
Public function Const const FStateTreeInstanceData *  
Public function Const T::FInstanceDataType &

GetInstanceData ( const T& Node
)

  
Public function Const T &  
Public function Const T *  
Public function Const TStateTreeInstanceDataStructRef< typename T::FInstanceDataType >

GetInstanceDataStructRef ( const T& Node
)

  
Protected function Virtual Const FString  
Public function Const EStateTreeRunStatus  
Public function Const const FStateTreeReference *  
Public function Const FStateTreeEventQueue &  
Public function TArrayView< FStateTreeSharedEvent >  
Public function Const FStateTreeInstanceData *  
Public function Const UObject *  
Public function Const TConstArrayView< FRecordedStateTreeTransitionResult > Returns the recorded transitions for this context.
Protected function Const FString

GetSafeStateName ( const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeStateHandle State
)

  
Public function Const int32  
Public function Const const FCompactStateTreeState *  
Protected function Const FString  
Public function Const const UStateTree *  
Public function Const EStateTreeRunStatus  
Public function Const UWorld *  
Public function Const bool  
Protected function Const bool

IsHandleSourceValid ( const FStateTreeExecutionFrame* ParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeDataHandle Handle
)

  
Public function Const bool

IsValid ()

  
Protected function bool

RequestTransition ( const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeStateHandle NextState,
const EStateTreeTransitionPriority Priority,
const FStateTreeSharedEvent* TransitionEvent,
const EStateTreeSelectionFallback Fallback
)

 Requests transition to a specified state with specified priority.
Public function void Requests transition to a state.
Protected function bool

SelectState ( const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeStateHandle NextState,
FStateSelectionResult& OutSelectionResult,
const FStateTreeSharedEvent* TransitionEvent,
const EStateTreeSelectionFallback Fallback
)

 Runs state selection logic starting at the specified state, walking towards the leaf states.
Protected function bool

SelectStateInternal ( const FStateTreeExecutionFrame* CurrentParentFrame,
FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeExecutionFrame* CurrentFrameInActiveFrames,
TConstArrayView< FStateTreeStateHandle > PathToNextState,
FStateSelectionResult& OutSelectionResult,
const FStateTreeSharedEvent* TransitionEvent
)

 Used internally to do the recursive part of the SelectState().
Public function Const void

SendEvent ( const FGameplayTag Tag,
const FConstStructView Payload,
const FName Origin
)

 Sends event for the StateTree.
Public function void Sets callback used to collect external data views during State Tree execution.
Public function void Sets context data view value for specific item.
Public function bool

SetContextDataByName ( const FName Name,
FStateTreeDataView DataView
)

 Sets the context data based on name (name is defined in the schema), returns true if data was found
Public function void Updates data view of the parameters by using the default values defined in the StateTree asset.
Public function void Sets external data view value for specific item.
Protected function bool

SetGlobalParameters ( const FInstancedPropertyBag& Parameters
)

 Stores copy of provided parameters as State Tree global parameters.
Public function void

SetLinkedStateTreeOverrides ( const FStateTreeReferenceOverrides* InLinkedStateTreeOverrides
)

  
Public function void

SetParameters ( const FInstancedPropertyBag& Parameters
)

 Updates data view of the parameters by replacing the default values defined in the StateTree asset by the provided values.
Protected function void

SetupNextTransition ( const FStateTreeExecutionFrame& CurrentFrame,
const FStateTreeStateHandle NextState,
const EStateTreeTransitionPriority Priority
)

 Sets up NextTransition based on the provided parameters and the current execution status.
Public function EStateTreeRunStatus

Start ( const FInstancedPropertyBag* InitialParameters,
int32 RandomSeed
)

 Start executing.
Protected function EStateTreeRunStatus

StartEvaluatorsAndGlobalTasks ( FStateTreeIndex16& OutLastInitializedTaskIndex
)

 Starts evaluators and global tasks.
Protected function EStateTreeRunStatus Starts temporary instances of global evaluators and tasks for a given frame.
Protected function void Handles logic for signalling State completed.
Public function EStateTreeRunStatus

Stop ( const EStateTreeRunStatus CompletionStatus
)

 Stop executing if the tree is running.
Protected function void

StopEvaluatorsAndGlobalTasks ( const EStateTreeRunStatus CompletionStatus,
const FStateTreeIndex16 LastInitializedTaskIndex
)

 Stops evaluators and global tasks.
Protected function void Stops temporary global evaluators and tasks for the provided frame.
Protected function bool

TestAllConditions ( const FStateTreeExecutionFrame* CurrentParentFrame,
const FStateTreeExecutionFrame& CurrentFrame,
const int32 ConditionsOffset,
const int32 ConditionsNum
)

 Checks all conditions at given range
Public function EStateTreeRunStatus

Tick ( const float DeltaTime
)

 Tick the state tree logic, updates the tasks and triggers transitions.
Protected function EStateTreeRunStatus

TickEvaluatorsAndGlobalTasks ( const float DeltaTime,
bool bTickGlobalTasks
)

 Tick evaluators and global tasks by delta time.
Protected function EStateTreeRunStatus  
Protected function EStateTreeRunStatus Common functionality shared by the tick methods.
Protected function EStateTreeRunStatus

TickTasks ( const float DeltaTime
)

 Ticks tasks of all active states starting from current state by delta time.
Public function EStateTreeRunStatus Tick the state tree logic partially, triggers the transitions.
Protected function void Handles transition triggering part of the tick.
Public function EStateTreeRunStatus

TickUpdateTasks ( const float DeltaTime
)

 Tick the state tree logic partially, updates the tasks.
Protected function void

TickUpdateTasksInternal ( const float DeltaTime
)

 Handles task ticking part of the tick.
Protected function bool Triggers transitions based on current run status.
Protected function void

UpdateInstanceData ( TConstArrayView< FStateTreeExecutionFrame > CurrentActiveFrames,
TArrayView< FStateTreeExecutionFrame > NextActiveFrames
)

  

Classes

  Type Name Description
Protected struct FAllowDirectTransitionsScope Helper struct to track when it is allowed to request transitions.  
Protected struct FCollectedExternalDataCache    
Protected struct FCurrentFrameStateSelectionEventsScope Helper struct to track currently processed state selection events.  
Protected struct FCurrentlyProcessedFrameScope Helper struct to track currently processed frame.  
Protected struct FCurrentlyProcessedStateScope Helper struct to track currently processed state.  
Protected struct FCurrentlyProcessedTransitionEventScope Helper struct to track currently processed transition event.  
Protected struct FNodeInstanceDataScope Helper struct to set current node data.  
Protected struct FStateSelectionResult Describes a result of States Selection.  

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