Textures.h

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/** @noop License Comment
 *  @file
 *  @copyright
 *  This Source Code is subject to the terms of the Mozilla Public License, v2.0.
 *  If a copy of the MPL was not distributed with this file You can obtain one at
 *  https://mozilla.org/MPL/2.0/
 *  
 *  @author David Mórász
 *  @date 2025
 */
 
#pragma once
 
#include "CoreMinimal.h"
#include "Mcro/Concepts.h"
#include "Mcro/AssertMacros.h"
#include "Engine/TextureRenderTarget2D.h"
 
/** This namespace contain utilities regarding high-level cross-platform and cross-rhi texture objects */
namespace Mcro::Rendering::Textures
{
    using namespace Mcro::Concepts;
    
    /** Get the lower level RHI texture from a high level UTexture2D object if it's possible, nullptr otherwise */
    MCRO_API FRHITexture* GetRhiTexture2D(UTexture* target);
 
    /** Describing a struct which can give texture size and layout information */
    template <typename T>
    concept CTextureSize = requires(T t, typename T::FormatType)
    {
        t.Width;
        t.Height;
        t.Format;
    };
 
    /** Specialize this function template to define the unknown format for an RHI texture format */
    template <CEnum FormatType>
    constexpr auto GetUnknownFormat() { return static_cast<FormatType>(0); }
 
    template <> constexpr auto GetUnknownFormat<EPixelFormat>() { return PF_Unknown; }
    template <> constexpr auto GetUnknownFormat<ETextureRenderTargetFormat>() { return RTF_R8; }
 
    /** Specialize this function template to define format conversion of equivalent formats between RHIs */
    template <CEnum ToFormatType, CEnum FromFormatType>
    requires (!CSameAs<ToFormatType, FromFormatType>)
    ToFormatType ConvertFormat(FromFormatType from)
    {
        return static_cast<ToFormatType>(from);
    }
 
    /** Special case when ToFormatType and FromFormatType are the same there's no need for conversion */
    template <CEnum ToFormatType, CEnum FromFormatType>
    requires CSameAs<ToFormatType, FromFormatType>
    ToFormatType ConvertFormat(FromFormatType from)
    {
        return from;
    }
 
    template <>
    FORCEINLINE_DEBUGGABLE ETextureRenderTargetFormat ConvertFormat<ETextureRenderTargetFormat, EPixelFormat>(EPixelFormat from)
    {
        switch (from)
        {
        case PF_G8: return RTF_R8;
        case PF_R8G8: return RTF_RG8;
        case PF_B8G8R8A8: return RTF_RGBA8;
 
        case PF_R16F: return RTF_R16f;
        case PF_G16R16F: return RTF_RG16f;
        case PF_FloatRGBA: return RTF_RGBA16f;
 
        case PF_R32_FLOAT: return RTF_R32f;
        case PF_G32R32F: return RTF_RG32f;
        case PF_A32B32G32R32F: return RTF_RGBA32f;
        case PF_A2B10G10R10: return RTF_RGB10A2;
        default:
            {
                ASSERT_QUIT(false, RTF_R8,
                    ->WithMessageF(TEXT("Unhandled ETextureRenderTargetFormat entry %s"), GetPixelFormatString(from))
                )
                return RTF_R8;
            };
        }
    }
    
    template <>
    FORCEINLINE_DEBUGGABLE EPixelFormat ConvertFormat<EPixelFormat, ETextureRenderTargetFormat>(ETextureRenderTargetFormat from)
    {
        // I know about GetPixelFormatFromRenderTargetFormat but I also have better error handling
        switch (from)
        {
        case RTF_R8: return PF_G8;
        case RTF_RG8: return PF_R8G8;
        case RTF_RGBA8: return PF_B8G8R8A8;
        case RTF_RGBA8_SRGB: return PF_B8G8R8A8;
 
        case RTF_R16f: return PF_R16F;
        case RTF_RG16f: return PF_G16R16F;
        case RTF_RGBA16f: return PF_FloatRGBA;
 
        case RTF_R32f: return PF_R32_FLOAT;
        case RTF_RG32f: return PF_G32R32F;
        case RTF_RGBA32f: return PF_A32B32G32R32F;
        case RTF_RGB10A2: return PF_A2B10G10R10;
        default:
            {
                auto enumName = UEnum::GetValueAsString(from);
                ASSERT_QUIT(false, PF_Unknown,
                    ->WithMessageF(TEXT("Unhandled ETextureRenderTargetFormat entry %s"), *enumName)
                );
                return PF_Unknown;
            }
        }
    }
 
    /**
     *  A simple texture size description which can be used for checking the need to recreate a texture resource.
     *  
     *  @todo This may get generalized to other type of resources in the future.
     *  @tparam SizeType      the integral type for texture size
     *  @tparam InFormatType  the type of the format enum
     */
    template <CScalar SizeType, CEnum InFormatType>
    struct TTextureSize
    {
        using FormatType = InFormatType;
        
        TTextureSize() {};
        
        template <CScalar SizeTypeArg, CEnum FormatTypeArg>
        TTextureSize(SizeTypeArg width, SizeTypeArg height, FormatTypeArg format)
            : Width(static_cast<SizeType>(width))
            , Height(static_cast<SizeType>(height))
            , Format(ConvertFormat<InFormatType>(format))
        {}
 
        template <CTextureSize OtherTextureSize>
        TTextureSize(OtherTextureSize const& other)
            : Width(static_cast<SizeType>(other.Width))
            , Height(static_cast<SizeType>(other.Height))
            , Format(ConvertFormat<InFormatType>(other.Format))
        {}
 
        template <CTextureSize OtherTextureSize>
        TTextureSize(OtherTextureSize&& other)
            : Width(static_cast<SizeType>(other.Width))
            , Height(static_cast<SizeType>(other.Height))
            , Format(ConvertFormat<InFormatType>(other.Format))
        {}
        
        SizeType Width = 0;
        SizeType Height = 0;
        InFormatType Format = GetUnknownFormat<InFormatType>();
        
        operator bool() const
        {
            return Width > 0 && Height > 0 && Format != GetUnknownFormat<InFormatType>();
        }
 
        template <CTextureSize OtherTextureSize>
        operator OtherTextureSize() const
        {
            return OtherTextureSize(
                Width, Height,
                ConvertFormat<typename OtherTextureSize::FormatType>(Format)
            );
        }
    };
 
    template <CTextureSize Left, CTextureSize Right>
    bool operator == (Left const& l, Right const& r)
    {
        return l.Width == r.Width
            && l.Height == r.Height
            && l.Format == ConvertFormat<typename Left::FormatType>(r.Format)
        ;
    }
    
    template <CTextureSize Left, CTextureSize Right>
    bool operator != (Left const& l, Right const& r) { return !(l == r); }
 
    using FUnrealTextureSize = TTextureSize<uint32, EPixelFormat>;
 
    MCRO_API FUnrealTextureSize GetTextureSize(UTexture* texture);
}