DelayedDrag.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "InputCoreTypes.h"
#include "Framework/Application/SlateApplication.h"
 
class FDelayedDrag
{
public:
 
    FDelayedDrag(FVector2D InInitialPosition, FKey InEffectiveKey)
        : InitialPosition(InInitialPosition), bHasInitiatedDrag(false), DistanceDragged(0), EffectiveKey(InEffectiveKey)
    {
        TriggerDistance = FSlateApplication::Get().GetDragTriggerDistance();
    }
 
    const FVector2D& GetInitialPosition() const { return InitialPosition; }
 
    bool IsDragging() const { return bHasInitiatedDrag; }
 
    void ForceDragStart() { bHasInitiatedDrag = true; }
 
    bool AttemptDragStart(const FPointerEvent& MouseEvent)
    {
        if (!bHasInitiatedDrag && MouseEvent.IsMouseButtonDown(EffectiveKey))
        {
            DistanceDragged += MouseEvent.GetCursorDelta().Size();
            if (!bHasInitiatedDrag && DistanceDragged > TriggerDistance)
            {
                ForceDragStart();
                return true;
            }
        }
        return false;
    }
 
    void SetTriggerScaleFactor(float InTriggerScaleFactor)
    {
        TriggerDistance = FMath::Max(FSlateApplication::Get().GetDragTriggerDistance() * InTriggerScaleFactor, 1.f);
    }
 
protected:
 
    FVector2D InitialPosition;
    bool bHasInitiatedDrag;
    float DistanceDragged;
    float TriggerDistance;
    FKey EffectiveKey;
};