Make the arbitrary mipmap detection threshold configureable

This is likely a "superuser" option at best, but I want to be able to play with
it without rebuilding if I want to tweak the heuristics

Source/Core/Core/Config/GraphicsSettings.cpp

@@ -109,6 +109,8 @@ const ConfigInfo<bool> GFX_ENHANCE_DISABLE_COPY_FILTER{
     {System::GFX, "Enhancements", "DisableCopyFilter"}, true};
 const ConfigInfo<bool> GFX_ENHANCE_ARBITRARY_MIPMAP_DETECTION{
     {System::GFX, "Enhancements", "ArbitraryMipmapDetection"}, true};
+const ConfigInfo<float> GFX_ENHANCE_ARBITRARY_MIPMAP_DETECTION_THRESHOLD{
+    {System::GFX, "Enhancements", "ArbitraryMipmapDetectionThreshold"}, 4.5f};
 
 // Graphics.Stereoscopy
 

Source/Core/Core/Config/GraphicsSettings.h

@@ -86,6 +86,7 @@ extern const ConfigInfo<std::string> GFX_ENHANCE_POST_SHADER;
 extern const ConfigInfo<bool> GFX_ENHANCE_FORCE_TRUE_COLOR;
 extern const ConfigInfo<bool> GFX_ENHANCE_DISABLE_COPY_FILTER;
 extern const ConfigInfo<bool> GFX_ENHANCE_ARBITRARY_MIPMAP_DETECTION;
+extern const ConfigInfo<float> GFX_ENHANCE_ARBITRARY_MIPMAP_DETECTION_THRESHOLD;
 
 // Graphics.Stereoscopy
 

Source/Core/VideoCommon/TextureCacheBase.cpp

@@ -507,7 +507,7 @@ public:
     // expect a normal blurred mipmap to look like and what we actually received
     // 4.5% was chosen because it's just below the lowest clearly-arbitrary texture
     // I found in my tests, the background clouds in Mario Galaxy's Observatory lobby.
-    constexpr auto THRESHOLD_PERCENT = 4.5f;
+    const auto threshold = g_ActiveConfig.fArbitraryMipmapDetectionThreshold;
 
     auto* src = downsample_buffer;
     auto* dst = downsample_buffer + levels[1].shape.row_length * levels[1].shape.height * 4;
@@ -533,7 +533,7 @@ public:
     }
 
     auto all_levels = total_diff / (levels.size() - 1);
-    return all_levels > THRESHOLD_PERCENT;
+    return all_levels > threshold;
   }
 
 private:

Source/Core/VideoCommon/VideoConfig.cpp

@@ -121,6 +121,8 @@ void VideoConfig::Refresh()
   bForceTrueColor = Config::Get(Config::GFX_ENHANCE_FORCE_TRUE_COLOR);
   bDisableCopyFilter = Config::Get(Config::GFX_ENHANCE_DISABLE_COPY_FILTER);
   bArbitraryMipmapDetection = Config::Get(Config::GFX_ENHANCE_ARBITRARY_MIPMAP_DETECTION);
+  fArbitraryMipmapDetectionThreshold =
+      Config::Get(Config::GFX_ENHANCE_ARBITRARY_MIPMAP_DETECTION_THRESHOLD);
 
   stereo_mode = Config::Get(Config::GFX_STEREO_MODE);
   iStereoDepth = Config::Get(Config::GFX_STEREO_DEPTH);

Source/Core/VideoCommon/VideoConfig.h

@@ -75,6 +75,7 @@ struct VideoConfig final
   bool bForceTrueColor;
   bool bDisableCopyFilter;
   bool bArbitraryMipmapDetection;
+  float fArbitraryMipmapDetectionThreshold;
 
   // Information
   bool bShowFPS;