Added enforcing language with EnderalLanguage.ini

source/Enderal DLL/src/Main.cpp

@@ -16,6 +16,7 @@
 #include "Patches/PluginsTxtPatch.h"
 #include "Patches/FormTypeCollisionDetector.h"
 #include "Patches/GogVramLeakFix.h"
+#include "Patches/ForceLanguage.h"
 
 using namespace SKSE;
 
@@ -214,6 +215,8 @@ SKSEPluginLoad(const LoadInterface* skse) {
 
 	RE::INISettingCollection::GetSingleton()->GetSetting("sIntroSequence:General")->data.s = nullptr;
 
+	ForceLanguage::Install("Data/SKSE/Plugins/EnderalLanguage.ini");
+
 	EventListener::Install();
 
 	GetPapyrusInterface()->Register(Papyrus::Bind);

source/Enderal DLL/src/Patches/ForceLanguage.h

@@ -0,0 +1,115 @@
+#pragma once
+
+#include <SimpleIni.h>
+
+// Reads the language from Data/SKSE/Plugins/EnderalLanguage.ini and enforces it at runtime,
+// independently of sLanguage in Skyrim.ini.
+//
+// The engine keeps the active language in the string setting sLanguage:General and reads that
+// Setting's data.s directly (the object is statically allocated, so the reads are hardcoded
+// addresses) whenever it builds a localized path:
+//
+//   Strings\<plugin>_<language>.STRINGS / .DLSTRINGS / .ILSTRINGS
+//   Interface\Translate_<language>.txt
+//   Interface\Controls\<device>\<language>.txt
+//   credits_<language>.txt
+//
+// Overwriting data.s therefore switches the language everywhere at once, but only inside a narrow
+// window: INISettingCollection::ReadSetting puts the Skyrim.ini value back (that file does contain
+// sLanguage, unlike sIntroSequence), and TESDataHandler has already loaded the .STRINGS files by
+// the time SKSE dispatches kDataLoaded. Hooking ReadSetting sidesteps both problems - the value is
+// re-applied right after every read of that setting, whenever the engine reads the INI.
+class ForceLanguage final : public RE::INISettingCollection
+{
+public:
+	static void Install(const char* a_iniPath)
+	{
+		if (!ReadINI(a_iniPath)) {
+			return;
+		}
+
+		const auto collection = RE::INISettingCollection::GetSingleton();
+		setting = collection ? collection->GetSetting("sLanguage:General") : nullptr;
+
+		if (!setting) {
+			logger::error("sLanguage:General is missing, cannot enforce the language");
+			return;
+		}
+
+		REL::Relocation<uintptr_t> vtbl(RE::INISettingCollection::VTABLE[0]);
+		_ReadSetting = vtbl.write_vfunc(0x4, &ReadSettingEx);
+
+		Apply();
+
+		logger::info("Enforcing language {}", requested);
+	}
+
+private:
+	bool ReadSettingEx(RE::Setting* a_setting)
+	{
+		const auto result = _ReadSetting(this, a_setting);
+
+		if (a_setting == setting) {
+			Apply();
+		}
+
+		return result;
+	}
+
+	// The engine owns data.s once the setting is managed and may overwrite it in place with a value
+	// of equal or smaller length, so hand out a private buffer and restamp it from requested.
+	static void Apply()
+	{
+		strcpy_s(buffer, sizeof(buffer), requested.c_str());
+		setting->data.s = buffer;
+	}
+
+	static bool ReadINI(const char* a_iniPath)
+	{
+		if (!std::filesystem::exists(a_iniPath)) {
+			return false;
+		}
+
+		CSimpleIniA ini;
+		ini.SetUnicode(false);
+		ini.SetMultiKey(false);
+
+		if (const auto result = ini.LoadFile(a_iniPath); result != SI_OK) {
+			logger::error("Failed to read {} (error {})", a_iniPath, static_cast<int>(result));
+			return false;
+		}
+
+		// [General] mirrors Skyrim.ini, a section-less key is accepted as well.
+		requested = ini.GetValue("General", "sLanguage", ini.GetValue("", "sLanguage", ""));
+
+		constexpr auto whitespace = " \t\r\n"sv;
+		const auto first = requested.find_first_not_of(whitespace);
+		requested = first == std::string::npos
+			? std::string()
+			: requested.substr(first, requested.find_last_not_of(whitespace) - first + 1);
+
+		if (requested.empty()) {
+			logger::warn("{} has no sLanguage value, keeping the language from Skyrim.ini", a_iniPath);
+			return false;
+		}
+
+		if (requested.size() >= sizeof(buffer)) {
+			logger::error("sLanguage value \"{}\" in {} is too long", requested, a_iniPath);
+			requested.clear();
+			return false;
+		}
+
+		// Enderal ships its strings loose, so a missing file means the language is most likely misspelled.
+		const auto strings = std::format("Data/Strings/enderal - forgotten stories_{}.strings", requested);
+		if (!std::filesystem::exists(strings)) {
+			logger::warn("{} does not exist, {} may not be a supported language", strings, requested);
+		}
+
+		return true;
+	}
+
+	inline static std::string requested;            // as configured, never handed to the engine
+	inline static char buffer[64]{};                // what data.s points at, may be overwritten in place
+	inline static RE::Setting* setting{ nullptr };
+	inline static REL::Relocation<decltype(&ReadSettingEx)> _ReadSetting;
+};