Interactable Component Hold

What You'll Learn

• How hold progress stays consistent across server/client without replicating a timer
• Why releasing the key early cancels rather than pauses
• The idempotency guard that protects against duplicate InteractionStarted calls

Core Concepts

UMounteaInteractableComponentHold requires the interactor to hold the interaction key for InteractionPeriod seconds. It's the workhorse type for doors, levers, and any channeled action where duration itself is the point.

UMounteaInteractableComponentHold : public UMounteaInteractableComponentBase

Progress Without Timer Replication

float Progress = (ServerTime - InteractionStartServerTime) / InteractionPeriod;

InteractionStartServerTime is stamped once, server-side, on join, and replicated via OnRep_InteractionStartServerTime. Every client (and the server itself) computes progress from that single shared timestamp against its own read of AGameStateBase::GetServerWorldTimeSeconds() - there's no FTimerHandle state to replicate, and no clock-skew risk from comparing a server timestamp against a client's local clock.

Idempotency Guard

void UMounteaInteractableComponentHold::InteractionStarted_Implementation(...)
{
    if (GetWorld()->GetTimerManager().IsTimerActive(Timer_Hold))
        return;  // ignore repeat StartInteraction calls while already holding

    Super::InteractionStarted_Implementation(TimeStarted, CausingInteractor);
    GetWorld()->GetTimerManager().SetTimer(Timer_Hold, this,
        &UMounteaInteractableComponentHold::OnHoldCompleted, InteractionPeriod, false);
}

The guard sits before the Super:: call deliberately - the base InteractionStarted_Implementation unconditionally re-stamps InteractionStartServerTime on every invocation, so a guard placed only around the timer setup would still corrupt the client-visible progress percentage on a repeat call (e.g. Enhanced Input firing Triggered more than once for a held key in a single frame window).

Releasing Early Cancels

void UMounteaInteractableComponentHold::InteractionStopped_Implementation(...)
{
    GetWorld()->GetTimerManager().ClearTimer(Timer_Hold);
    Super::InteractionStopped_Implementation(TimeStarted, CausingInteractor);
}

StopInteraction before InteractionPeriod elapses clears the timer - there's no partial credit or resume-from-progress; the next StartInteraction re-stamps InteractionStartServerTime and starts the hold from zero.

See Interactable Component Hover, which extends this class to trigger from cursor dwell time instead of a held key. See Interactable System for the shared slot/state/lifecycle machinery.