SlateVectorArtInstanceData.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "Math/UnrealMathSSE.h"
#include "Math/Vector2D.h"
#include "Math/Vector4.h"
#include "Misc/AssertionMacros.h"
 
struct FSlateVectorArtInstanceData
{
public:
    const FVector4& GetData() const { return Data; }
    FVector4& GetData() { return Data; }
 
    UMG_API void SetPositionFixedPoint16(FVector2D Position);
    UMG_API void SetScaleFixedPoint16(float Scale);
 
    UMG_API void SetPosition(FVector2D Position);
    UMG_API void SetScale(float Scale);
    UMG_API void SetBaseAddress(float Address);
 
    template<int32 Component, int32 ByteIndex>
    void PackFloatIntoByte(float InValue)
    {
        PackByteIntoByte<Component, ByteIndex>(static_cast<uint8>(FMath::RoundToInt(InValue * 0xFFu)));
    }
 
    template<int32 Component, int32 ByteIndex>
    void PackByteIntoByte(uint8 InValue)
    {
        // Each float has 24 usable bits of mantissa, but we cannot access the bits directly.
        // We will not respect the IEEE "normalized mantissa" rules, so let 
        // the compiler/FPU do conversions from byte to float and vice versa for us.
 
        //Produces a value like 0xFFFF00FF; where the 00s are shifted by `Position` bytes.
        static const uint32 Mask = ~(0xFF << ByteIndex * 8);
 
        // Clear out a byte to OR with while maintaining the rest of the data intact.
        uint32 CurrentData = static_cast<uint32>(Data[Component]) & Mask;
        // OR in the value
        Data[Component] = CurrentData | (InValue << ByteIndex * 8);
    }
 
    template<int32 Component, int32 ByteIndex>
    void PackByteIntoByte(float InValue)
    {
        checkf(false, TEXT("PackByteIntoByte() being used with a float value. This is almost definitely an error. Use PackFloatIntoByte()."));
    }
 
protected:
    // LWC_TODO: should this and GetData() use FVector4f?
    FVector4 Data;
};