Accurate region detection for NAND titles

Source/Core/Core/IOS/ES/Formats.cpp

@@ -295,11 +295,16 @@ u16 TMDReader::GetGroupId() const
 
 DiscIO::Region TMDReader::GetRegion() const
 {
+  if (!IsChannel(GetTitleId()))
+    return DiscIO::Region::Unknown;
+
   if (GetTitleId() == Titles::SYSTEM_MENU)
     return DiscIO::GetSysMenuRegion(GetTitleVersion());
 
-  return DiscIO::CountryCodeToRegion(static_cast<u8>(GetTitleId() & 0xff),
-                                     DiscIO::Platform::WiiWAD);
+  const DiscIO::Region region =
+      static_cast<DiscIO::Region>(Common::swap16(m_bytes.data() + offsetof(TMDHeader, region)));
+
+  return region <= DiscIO::Region::NTSC_K ? region : DiscIO::Region::Unknown;
 }
 
 std::string TMDReader::GetGameID() const

Source/Core/Core/IOS/ES/Formats.h

@@ -201,8 +201,6 @@ public:
   u32 GetTitleFlags() const;
   u16 GetTitleVersion() const;
   u16 GetGroupId() const;
-
-  // Provides a best guess for the region. Might be inaccurate or Region::Unknown.
   DiscIO::Region GetRegion() const;
 
   // Constructs a 6-character game ID in the format typically used by Dolphin.

Source/Core/DiscIO/Enums.h

@@ -40,13 +40,13 @@ enum class Country
   NumberOfCountries
 };
 
-// Regions 0 - 2 and 4 match Nintendo's GameCube/Wii region numbering.
+// This numbering matches Nintendo's GameCube/Wii region numbering.
 enum class Region
 {
   NTSC_J = 0,   // Japan and Taiwan (and South Korea for GameCube only)
   NTSC_U = 1,   // Mainly North America
   PAL = 2,      // Mainly Europe and Oceania
-  Unknown = 3,  // 3 seems to be unused? Anyway, we need an Unknown entry. Let's put it here
+  Unknown = 3,  // Nintendo uses this to mean region free, but we also use it for unknown regions
   NTSC_K = 4    // South Korea (Wii only)
 };
 
@@ -62,8 +62,8 @@ enum class Language
   Spanish = 4,
   Italian = 5,
   Dutch = 6,
-  SimplifiedChinese = 7,
-  TraditionalChinese = 8,
+  SimplifiedChinese = 7,   // Not selectable on any unmodded retail Wii
+  TraditionalChinese = 8,  // Not selectable on any unmodded retail Wii
   Korean = 9,
   Unknown
 };

Source/Core/DiscIO/Volume.h

@@ -95,7 +95,6 @@ public:
   virtual Platform GetVolumeType() const = 0;
   virtual bool SupportsIntegrityCheck() const { return false; }
   virtual bool CheckIntegrity(const Partition& partition) const { return false; }
-  // May be inaccurate for WADs
   virtual Region GetRegion() const = 0;
   virtual Country GetCountry(const Partition& partition = PARTITION_NONE) const = 0;
   virtual BlobType GetBlobType() const = 0;

Source/Core/DiscIO/VolumeWad.cpp

@@ -84,11 +84,15 @@ Country VolumeWAD::GetCountry(const Partition& partition) const
   if (!m_tmd.IsValid())
     return Country::Unknown;
 
-  u8 country_code = static_cast<u8>(m_tmd.GetTitleId() & 0xff);
-  if (country_code == 2)  // SYSMENU
+  const u8 country_byte = static_cast<u8>(m_tmd.GetTitleId() & 0xff);
+  if (country_byte == 2)  // SYSMENU
     return TypicalCountryForRegion(GetSysMenuRegion(m_tmd.GetTitleVersion()));
 
-  return CountryCodeToCountry(country_code, Platform::WiiWAD);
+  const Region region = GetRegion();
+  if (CountryCodeToRegion(country_byte, Platform::WiiWAD, region) != region)
+    return TypicalCountryForRegion(region);
+
+  return CountryCodeToCountry(country_byte, Platform::WiiWAD, region);
 }
 
 const IOS::ES::TMDReader& VolumeWAD::GetTMD(const Partition& partition) const

Source/Core/DiscIO/VolumeWad.h

@@ -48,7 +48,6 @@ public:
     return "";
   }
   Platform GetVolumeType() const override;
-  // Provides a best guess for the region. Might be inaccurate or Region::Unknown.
   Region GetRegion() const override;
   Country GetCountry(const Partition& partition = PARTITION_NONE) const override;