UI Interfaces

A small set of Blueprint interfaces a game can implement to let the SDK drive its HUD, player, and minigame classes, plus two things that are not UI at all but live in the same module: the Blueprint reception layer, which forwards incoming events and actor updates to delegates without a line of C++, and UCrowdyUtilities, an entity and session helper library. All of it lives in CrowdyServices.

When you touch this

When you want the SDK to open and close your widgets instead of doing it by hand, when a Blueprint-only project needs to receive game events or actor updates without binding a delegate in C++, or when gameplay code needs an entity's id, owner, or host state and you would rather call a library function than reach into the entity component yourself.

Nothing else in the SDK requires any of this. CrowdyState and RPC work with none of ICrowdyHUD, ICrowdyUIRootWidget, ICrowdyPlayer, ICrowdyMinigame, or ACrowdyHUDBase implemented.

HUD hooks

ICrowdyUIRootWidget is the contract for a widget that owns the four UI layers and stacks widgets on them. ICrowdyHUD is the contract for a HUD actor that routes commands to that root widget. Each I interface is the Blueprint-facing half of a UINTERFACE pair; the generated class you never call directly is UCrowdyUIRootWidget for the first and UCrowdyHUD for the second. ACrowdyHUDBase (Blueprintable, Abstract, derives AHUD) implements ICrowdyHUD for you and adds two editable properties, HUDWidgetClass and WidgetSetConfig. UW_CrowdyHUD is the SDK's own UUserWidget implementation of ICrowdyUIRootWidget. HUDWidgetClass defaults to none: make a Widget Blueprint parented to UW_CrowdyHUD with four Overlay widgets named GameLayer, GameMenuLayer, MenuLayer and ModalLayer, and assign it as HUD Widget Class on your HUD Blueprint's class defaults; until then BeginPlay logs a warning and starts no widget system.

Interface	Function	Does	Parameters that matter
ICrowdyUIRootWidget	PushToLayer	Creates and pushes a widget onto one of the four layers	Layer (ECrowdyUILayer), bClearLayerFirst, WidgetClass
ICrowdyUIRootWidget	PopFromLayer	Pops the top widget off a layer	Layer, bRemoveFromParent
ICrowdyUIRootWidget	GetLayer	Returns the UOverlay backing a layer	Layer
ICrowdyHUD	ExecuteUICommand (Execute Crowdy UI Command)	Routes an FGameplayTag command to the HUD	Command, bHideOtherWidgetsInLayer, bChangeInputMode
ICrowdyHUD	GetWidgetReference	Returns an already-created widget of the given class, or null	WidgetClass
ICrowdyHUD	ToggleLayerVisibility	Shows or hides a whole layer	Layer, bVisible
ACrowdyHUDBase	InitializeCrowdyWidgets	BlueprintNativeEvent called once from BeginPlay; the default creates every widget in WidgetSetConfig. Override to add to that and call the parent	none

UCrowdySDKSubsystem::OnCrowdyHUDReady (Crowdy HUD Ready, FOnCrowdyHUDReady, no parameters) fires once ACrowdyHUDBase has created every widget in WidgetSetConfig; bind it on the Crowdy SDK Subsystem when something must wait for the HUD to exist.

ECrowdyUILayer (GameLayer, GameMenuLayer, MenuLayer, ModalLayer) names the four layers. ECrowdyInputMode (Game, GameAndUI, UI) is the input mode a widget switches to. A widget set is a UCrowdyWidgetSet data asset, one FWidgetSpec per tag in its WidgetSpecMap, each spec carrying a WidgetClass, Layer, bClearLayerFirst, bStartVisible, and the entering and exiting input modes. ACrowdyHUDBase::WidgetSetConfig points at one; its private ToggleWidget and GetWidget do the actual show and lookup work behind ExecuteUICommand and GetWidgetReference.

Set both HUDWidgetClass and WidgetSetConfig on the HUD Blueprint's class defaults; they are saved with it.

This section has no example: the tables above are the reference.

Player and minigame hooks

ICrowdyPlayer::GetPlayerName and ICrowdyPlayer::InteractMessage (an interact prompt with a Message and a Duration) are the player-facing hooks, generated alongside UCrowdyPlayer. ICrowdyMinigame::GetMinigameName and ICrowdyMinigame::JoinMinigame are their minigame equivalents, generated alongside UCrowdyMinigame.

GetPlayerName and GetMinigameName are placeholders today.

Both are hooks the SDK never calls and never implements; whatever you return is yours, and nothing in the SDK reads it. Do not build a feature that expects the SDK to fill either one.

The Blueprint reception layer

UCrowdyBlueprintReceptionLayer lets a Blueprint receive game events and actor updates without binding a delegate in C++. CreateAndRegisterLayer(WorldContextObject, Class) spawns one and registers it. Once registered, it broadcasts OnEventNotificationReceived (an FGameEventNotificationBP) for a matching game event and OnActorUpdateReceived (an FActorUpdateNotificationBP) for a matching actor update.

Three EditDefaultsOnly arrays say what a layer subscribes to: SupportedResponseTypes (ECrowdyMessageType), SupportedActorUpdateTypes (FName), and SupportedEvents (the struct types to receive).

An empty SupportedEvents array is a catch-all when the event opcode is listed.

With SupportedEvents empty and Client Event Notification or Server Event Notification in SupportedResponseTypes, the layer receives every event no other layer claimed. With all three arrays empty it receives nothing. The same rule pairs SupportedActorUpdateTypes with Actor Update Notification: empty plus the opcode is every actor update, empty alone is none.

DispatchToBlueprint and the RegisterLayer internals are C++-only and not exposed to Blueprint; RegisterLayer is safe to call more than once and builds one subscription per declared type, or the unclaimed fallback when nothing is declared and the matching opcode is listed.

The utilities library

UCrowdyUtilities is a static Blueprint function library for entities, sessions, and events. It is not UI-specific, but it lives in the same module.

Function	Does
SpawnCrowdyEntity, DestroyCrowdyEntity	Spawns or destroys an entity actor
GetCrowdyEntityID, GetCrowdyEntity	Converts between an entity actor and its id
GetLocalPlayerEntityID	The local player's entity id
GetCrowdyEntityOwnerID, GetAllCrowdyEntitiesByOwner	An entity's owner, or every entity a given owner has
CrowdyIsEntityRegistered	Whether an id is a known entity
GetCrowdyEntityRole	An entity's ECrowdyRole
DoesCrowdyEntityOwn	Whether one actor owns another, by Crowdy identity
GetCrowdyEntityComponent	An actor's entity component, falling back to FindComponentByClass when the actor does not implement ICrowdyEntityComponentProvider
IsCrowdyEntityLocallyControlled, IsCrowdyEntityPlayerControlled (and its exec-flow twin SwitchIsCrowdyEntityPlayerControlled)	Local or player control checks
CrowdyIsRemoteProxy (and its exec-flow twin SwitchCrowdyIsRemoteProxy)	Whether this is a remote proxy of the entity
K2_SendCrowdyEvent (display name Send Crowdy Event; C++-only template SendCrowdyEvent<T> for the same call without the Blueprint thunk)	Sends a game event struct with Recipient, DecayRate, and ReplicationDistance
CrowdyHasAuthority (exec-flow, Switch Crowdy Has Authority) / GetCrowdyHasAuthority (pure, Crowdy Has Authority)	True when this client is the host
CrowdyIsConnectedToServer	Whether the realtime connection is up
CrowdyGetHostID	The current host's id
IsCrowdyEntityHost	Whether this actor is the host player's own entity (its id equals the host id). For "owned by the host" compare GetCrowdyEntityOwnerID with CrowdyGetHostID

DoesCrowdyEntityOwn compares Crowdy ownership, not AActor::GetOwner.

The name invites Unreal's actor-owner meaning, but this checks Crowdy entity ownership instead; it will not agree with AActor::GetOwner() for an entity whose Unreal owner was never set to match.

IsCrowdyEntityHost and IsCrowdyEntityLocallyControlled both fold in host election state. See Host election and Host authority for what "host" means before relying on either.

Gotchas

• Every hook on this page is optional. Nothing else in the SDK requires an implementation of any of them.
• GetPlayerName and GetMinigameName are placeholders the SDK never calls; nothing reads what you return.
• HUDWidgetClass defaults to none. Without a UW_CrowdyHUD Widget Blueprint assigned, the HUD base starts no widget system and OnCrowdyHUDReady never fires.
• The reception layer's SupportedEvents is a claim list, not a filter: empty plus the event opcode in SupportedResponseTypes widens the layer to every unclaimed event; empty alone receives nothing.
• The reception layer forwards transport-level notifications to Blueprint.
• Everything on this page logs under LogCrowdyServices, gated by two trace CVars: crowdy.services.trace (CrowdyServicesTrace::Services) for the utilities library and reception layer, and crowdy.hud.trace (CrowdyServicesTrace::Hud) for HUD-side calls.

Related

• Host election and Host authority: what IsCrowdyEntityHost and IsCrowdyEntityLocallyControlled fold in.
• Channels: the message plane the reception layer's subscriptions ride.