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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 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 FStateTreeDataHandle CurrentNodeDataHandle Currently processed nodes instance data.
Protected variable FStateTreeDataView CurrentNodeInstanceData  
Protected variable TArray< FStateTreeEvent, TConcurrentLinearArrayAllocator< FDefaultBlockAllocationTag > > EventsToProcess Events to process in current tick.
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 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 const UStateTree & RootStateTree The StateTree asset the context is initialized for

Constructors

  Type Name Description
Public function  

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

  

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 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.
Protected function Const 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 Const 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

ExitState ( const FStateTreeTransitionResult& Transition
)

 Handles logic for exiting State.
Public function Const void

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 Const 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
)

  
Protected function Const FStateTreeDataView

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

  
Public function Const const FStateTreeEventQueue &  
Public function Const TConstArrayView< FStateTreeEvent >  
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 &  
Public function Const T::FInstanceDataType &

GetInstanceData ( const T& Node
)

  
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 FStateTreeEventQueue &  
Public function Const FStateTreeInstanceData * @retuen mutable references to the instance data in use, or nullptr if the context is not valid.
Public function Const UObject *  
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 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,
TArray< FStateTreeExecutionFrame, TFixedAllocator< MaxExecutionFrames > >& OutNextActiveFrames,
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,
const FStateTreeStateHandle NextStateHandle,
TArray< FStateTreeExecutionFrame, TFixedAllocator< MaxExecutionFrames > >& OutNextActiveFrames
)

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

SendEvent ( const FStateTreeEvent& Event
)

 Sends event for the StateTree.
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 Stores copy of provided parameters as State Tree global parameters.
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
)

 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 leftover global evaluators and tasks in the provided temporary instance data.
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.
Protected function EStateTreeRunStatus

TickEvaluatorsAndGlobalTasks ( const float DeltaTime,
bool bTickGlobalTasks
)

 Tick evaluators and global tasks by delta time.
Protected function EStateTreeRunStatus

TickTasks ( const float DeltaTime
)

 Ticks tasks of all active states starting from current state by delta time.
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 FCurrentlyProcessedFrameScope Helper struct to track currently processed frame.  
Protected struct FCurrentlyProcessedStateScope Helper struct to track currently processed state.  
Protected struct FNodeInstanceDataScope Helper struct to set current node data.  

Constants

Name Description
MaxExecutionFrames Max number of execution frames handled during state selection.

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