Merge pull request #5795 from JosJuice/gc-region-detection

Improve GameCube region detection

Source/Core/DiscIO/Enums.cpp

@@ -48,7 +48,7 @@ Country TypicalCountryForRegion(Region region)
 Region RegionSwitchGC(u8 country_code)
 {
   Region region = RegionSwitchWii(country_code);
-  return region == Region::NTSC_K ? Region::UNKNOWN_REGION : region;
+  return region == Region::NTSC_K ? Region::NTSC_J : region;
 }
 
 Region RegionSwitchWii(u8 country_code)

Source/Core/DiscIO/Enums.h

@@ -40,10 +40,10 @@ enum class Country
   NUMBER_OF_COUNTRIES
 };
 
-// Regions 0 - 2 and 4 match Nintendo's Wii region numbering.
+// Regions 0 - 2 and 4 match Nintendo's GameCube/Wii region numbering.
 enum class Region
 {
-  NTSC_J = 0,          // Japan and Taiwan
+  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_REGION = 3,  // 3 seems to be unused? Anyway, we need an UNKNOWN_REGION. Let's put it here
@@ -71,11 +71,16 @@ enum class Language
 bool IsDisc(Platform volume_type);
 bool IsWii(Platform volume_type);
 bool IsNTSC(Region region);
+
 Country TypicalCountryForRegion(Region region);
+// Avoid using this function if you can. Country codes aren't always reliable region indicators.
 Region RegionSwitchGC(u8 country_code);
+// Avoid using this function if you can. Country codes aren't always reliable region indicators.
 Region RegionSwitchWii(u8 country_code);
 Country CountrySwitch(u8 country_code);
+
 Region GetSysMenuRegion(u16 title_version);
 std::string GetSysMenuVersionString(u16 title_version);
+
 std::string GetCompanyFromID(const std::string& company_id);
 }

Source/Core/DiscIO/Volume.h

@@ -83,6 +83,7 @@ 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;
   Country GetCountry() const { return GetCountry(GetGamePartition()); }
   virtual Country GetCountry(const Partition& partition) const = 0;

Source/Core/DiscIO/VolumeGC.cpp

@@ -60,14 +60,31 @@ std::string VolumeGC::GetGameID(const Partition& partition) const
 
 Region VolumeGC::GetRegion() const
 {
-  const std::optional<u8> country_code = ReadSwapped<u8>(3, PARTITION_NONE);
-  return country_code ? RegionSwitchGC(*country_code) : Region::UNKNOWN_REGION;
+  const std::optional<u32> region_code = ReadSwapped<u32>(0x458, PARTITION_NONE);
+  if (!region_code)
+    return Region::UNKNOWN_REGION;
+  const Region region = static_cast<Region>(*region_code);
+  return region <= Region::PAL ? region : Region::UNKNOWN_REGION;
 }
 
 Country VolumeGC::GetCountry(const Partition& partition) const
 {
-  const std::optional<u8> country_code = ReadSwapped<u8>(3, partition);
-  return country_code ? CountrySwitch(*country_code) : Country::COUNTRY_UNKNOWN;
+  // The 0 that we use as a default value is mapped to COUNTRY_UNKNOWN and UNKNOWN_REGION
+  const u8 country = ReadSwapped<u8>(3, partition).value_or(0);
+  const Region region = GetRegion();
+
+  // Korean GC releases use NTSC-J.
+  // E is normally used for America, but it's also used for English-language Korean GC releases.
+  // K is used by games that are in the Korean language.
+  // W means Taiwan for Wii games, but on the GC, it's used for English-language Korean releases.
+  // (There doesn't seem to be any pattern to which of E and W is used for Korean GC releases.)
+  if (region == Region::NTSC_J && (country == 'E' || country == 'K' || country == 'W'))
+    return Country::COUNTRY_KOREA;
+
+  if (RegionSwitchGC(country) != region)
+    return TypicalCountryForRegion(region);
+
+  return CountrySwitch(country);
 }
 
 std::string VolumeGC::GetMakerID(const Partition& partition) const

Source/Core/DiscIO/VolumeWad.h

@@ -50,6 +50,7 @@ public:
     return "";
   }
   Platform GetVolumeType() const override;
+  // Provides a best guess for the region. Might be inaccurate or UNKNOWN_REGION.
   Region GetRegion() const override;
   Country GetCountry(const Partition& partition = PARTITION_NONE) const override;
 

Source/Core/DiscIO/VolumeWii.cpp

@@ -233,7 +233,10 @@ std::string VolumeWii::GetGameID(const Partition& partition) const
 Region VolumeWii::GetRegion() const
 {
   const std::optional<u32> region_code = m_pReader->ReadSwapped<u32>(0x4E000);
-  return region_code ? static_cast<Region>(*region_code) : Region::UNKNOWN_REGION;
+  if (!region_code)
+    return Region::UNKNOWN_REGION;
+  const Region region = static_cast<Region>(*region_code);
+  return region <= Region::NTSC_K ? region : Region::UNKNOWN_REGION;
 }
 
 Country VolumeWii::GetCountry(const Partition& partition) const