Subject: [PATCH] Resolve relative d4r library paths against the OptiScaler folder

Lets a drag-in d4r install ship OptiScaler.ini with NvngxPath=d4r instead of
an absolute path that only an installer could know. Absolute paths behave
exactly as before.
---
diff --git a/OptiScaler/Config.cpp b/OptiScaler/Config.cpp
--- a/OptiScaler/Config.cpp
+++ b/OptiScaler/Config.cpp
@@ -787,9 +787,17 @@
         {
             MainDllPath.set_from_config(readWString("Libraries", "OptiDllPath"));
 
-            NvngxPath.set_from_config(readWString("Libraries", "NvngxPath"));
-            NVNGX_DLSS_Library.set_from_config(readWString("Libraries", "NvngxDlssPath"));
-            DLSSFeaturePath.set_from_config(readWString("Libraries", "NvngxFeaturePath"));
+            // A relative library folder (d4r drag-in installs use "d4r") is resolved
+            // against this DLL's folder, as LogFileName is. Absolute paths are unchanged.
+            auto libraryPath = [](std::optional<std::wstring> value) -> std::optional<std::wstring>
+            {
+                if (!value.has_value() || value->empty() || std::filesystem::path(*value).is_absolute())
+                    return value;
+                return (Util::DllPath().parent_path() / *value).lexically_normal().wstring();
+            };
+            NvngxPath.set_from_config(libraryPath(readWString("Libraries", "NvngxPath")));
+            NVNGX_DLSS_Library.set_from_config(libraryPath(readWString("Libraries", "NvngxDlssPath")));
+            DLSSFeaturePath.set_from_config(libraryPath(readWString("Libraries", "NvngxFeaturePath")));
             NvapiDllPath.set_from_config(readWString("Libraries", "NvapiPath"));
 
             FfxDx12Path.set_from_config(readWString("Libraries", "FfxDx12Path"));