SlateSdfGenerator.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
#include "CoreMinimal.h"
 
class FSlateSdfGenerator
{
public:
    using Ptr = TUniquePtr<FSlateSdfGenerator>;
 
    enum class ERequestResponse
    {
        SUCCESS = 0,
        SDF_UNAVAILABLE,
        BUSY,
        PLACEHOLDER_ONLY,
        BAD_REQUEST
    };
 
    enum class ESdfType
    {
        Simple,
        Perpendicular,
        MultichannelAndSimple
    };
 
    struct FRequestOutputInfo
    {
        uint16 ImageWidth;
        uint16 ImageHeight;
        int16 BearingX;
        int16 BearingY;
    };
 
    struct FRequestDescriptor
    {
        TWeakPtr<class FFreeTypeFace> FontFace;
        uint32 GlyphIndex;
        ESdfType SdfType;
        float EmOuterSpread;
        float EmInnerSpread;
        int32 Ppem;
    };
 
    using FForEachRequestDoneCallback = TFunctionRef<void(const FRequestDescriptor/*RequestId*/, 
        TArray<uint8>/*RawPixels*/)>;
 
    virtual ~FSlateSdfGenerator();
 
    virtual ERequestResponse Spawn(const FRequestDescriptor& InRequest, FRequestOutputInfo& OutCharInfo) = 0;
    virtual ERequestResponse SpawnWithPlaceholder(const FRequestDescriptor& InRequest, FRequestOutputInfo& OutCharInfo, TArray<uint8>& OutRawPixels) = 0;
    virtual ERequestResponse Respawn(const FRequestDescriptor& InRequest, const FRequestOutputInfo& InCharInfo) = 0;
    virtual ERequestResponse MakePlaceholder(const FRequestDescriptor& InRequest, FRequestOutputInfo& OutCharInfo, TArray<uint8>& OutRawPixels) = 0;
    virtual void Update(const FForEachRequestDoneCallback& InEnumerator) = 0;
    virtual void Flush() = 0;
 
    static Ptr create();
 
protected:
    FSlateSdfGenerator();
 
};