ShaderPlatformCachedIniValue.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "HAL/IConsoleManager.h"
#include "RHIShaderPlatform.h"
#include "RHIStrings.h"
 
RENDERCORE_API EShaderPlatform GetEditorShaderPlatform(EShaderPlatform ShaderPlatform);
 
template<typename Type>
struct FShaderPlatformCachedIniValue
{
    FShaderPlatformCachedIniValue(const TCHAR* InCVarName)
        : CVarName(InCVarName)
        , CVar(nullptr)
    {
    }
 
    FShaderPlatformCachedIniValue(IConsoleVariable* InCVar)
        : CVar(InCVar)
    {
    }
 
    Type Get(EShaderPlatform ShaderPlatform)
    {
        Type Value{};
 
        const EShaderPlatform ActualShaderPlatform = GetEditorShaderPlatform(ShaderPlatform);
 
        FName IniPlatformName = ShaderPlatformToPlatformName(ActualShaderPlatform);
        // find the cvar if needed
        if (CVar == nullptr)
        {
            CVar = IConsoleManager::Get().FindConsoleVariable(*CVarName);
        }
 
        // if we are looking up our own platform, just use the current value, however
        // ShaderPlatformToPlatformName can return the wrong platform than expected - for instance, Linux Vulkan will return Windows
        // so instead of hitting an asser below, we detect that the request SP is the current SP, and use the CVar value that is set currently
        if (IniPlatformName == FPlatformProperties::IniPlatformName() || ActualShaderPlatform == GMaxRHIShaderPlatform)
        {
            checkf(CVar != nullptr, TEXT("Failed to find CVar %s when getting current value for FShaderPlatformCachedIniValue"), *CVarName);
 
            CVar->GetValue(Value);
            return Value;
        }
 
#if ALLOW_OTHER_PLATFORM_CONFIG
        // create a dummy cvar if needed
        if (CVar == nullptr)
        {
            // this could be a cvar that only exists on the target platform so create a dummy one
            CVar = IConsoleManager::Get().RegisterConsoleVariable(*CVarName, Type(), TEXT(""), ECVF_ReadOnly);
        }
 
        // now get the value from the platform that makes sense for this shader platform
        TSharedPtr<IConsoleVariable> OtherPlatformVar = CVar->GetPlatformValueVariable(IniPlatformName);
        ensureMsgf(OtherPlatformVar.IsValid(), TEXT("Failed to get another platform's version of a cvar (possible name: '%s'). It is probably an esoteric subclass that needs to implement GetPlatformValueVariable."), *CVarName);
        if (OtherPlatformVar.IsValid())
        {
            OtherPlatformVar->GetValue(Value);
        }
        else
        {
            // get this platform's value, even tho it could be wrong
            CVar->GetValue(Value);
        }
#else
        checkf(IniPlatformName == FName(FPlatformProperties::IniPlatformName()), TEXT("FShaderPlatformCachedIniValue can only look up the current platform when ALLOW_OTHER_PLATFORM_CONFIG is false"));
#endif
        return Value;
    }
 
private:
    FString CVarName;
    IConsoleVariable* CVar;
};