From 9141ff453b72dbf7cf2aa53ad46612ab67bc8cae Mon Sep 17 00:00:00 2001
From: bicarus <202771338+bicarus-dev@users.noreply.github.com>
Date: Tue, 4 Aug 2026 09:04:29 -0700
Subject: [PATCH] lang: detect forced UTF-8 ACP, try to opt-out (#853)

## Link to GitHub Issue or related Pull Request, if one exists
n/a

## Description of change

Fixes broken Japanese text when Windows `Use Unicode UTF-8 for worldwide
language support` setting is enabled. This setting changes the system
ACP to UTF-8 (65001), causing legacy Shift-JIS lead-byte checks to fail.

Windows 11: requests the legacy process code page through the manifest.

Windows 10: detects ACP 65001 (UTF-8), warns the user via deferred log,
and applies compatibility hook (only for popn pika model for now)

Windows 7 and below - UTF-8 option doesn't exist.

## Testing
---
 src/spice2x/build/manifest.manifest |  1 +
 src/spice2x/hooks/lang.cpp          | 45 +++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/src/spice2x/build/manifest.manifest b/src/spice2x/build/manifest.manifest
index f4d072b..d19d2e9 100644
--- a/src/spice2x/build/manifest.manifest
+++ b/src/spice2x/build/manifest.manifest
@@ -6,6 +6,7 @@
         <asmv3:windowsSettings xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
             <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2</dpiAwareness>
             <dpiAware>true</dpiAware>
+            <activeCodePage xmlns="http://schemas.microsoft.com/SMI/2019/WindowsSettings">Legacy</activeCodePage>
         </asmv3:windowsSettings>
     </asmv3:application>
     <dependency>
diff --git a/src/spice2x/hooks/lang.cpp b/src/spice2x/hooks/lang.cpp
index 99a4f32..553b966 100644
--- a/src/spice2x/hooks/lang.cpp
+++ b/src/spice2x/hooks/lang.cpp
@@ -13,7 +13,9 @@
 #include "avs/game.h"
 #include "games/iidx/iidx.h"
 #include "games/gitadora/gitadora.h"
+#include "games/popn/popn.h"
 #include "games/sdvx/sdvx.h"
+#include "util/deferlog.h"
 #include "util/detour.h"
 #include "util/logging.h"
 #include "util/utils.h"
@@ -29,6 +31,7 @@ static decltype(GetLocaleInfoEx) *GetLocaleInfoEx_orig = nullptr;
 #ifdef SPICE64
 static decltype(GetSystemDefaultLCID) *GetSystemDefaultLCID_orig = nullptr;
 static decltype(IsDBCSLeadByte) *IsDBCSLeadByte_orig = nullptr;
+static decltype(IsDBCSLeadByteEx) *IsDBCSLeadByteEx_orig = nullptr;
 static decltype(WideCharToMultiByte) *WideCharToMultiByte_orig = nullptr;
 static decltype(GetLocaleInfoA) *GetLocaleInfoA_orig = nullptr;
 static decltype(GetThreadLocale) *GetThreadLocale_orig = nullptr;
@@ -182,9 +185,30 @@ static BOOL WINAPI IsDBCSLeadByte_hook (
     BYTE TestChar
     )
 {
+    if (IsDBCSLeadByteEx_orig) {
+        return IsDBCSLeadByteEx_orig(CODEPAGE_SHIFT_JIS, TestChar);
+    }
+
     return IsDBCSLeadByteEx(CODEPAGE_SHIFT_JIS, TestChar);
 }
 
+static BOOL WINAPI IsDBCSLeadByteEx_hook(
+    UINT CodePage,
+    BYTE TestChar)
+{
+    switch (CodePage) {
+        case CP_ACP:
+        case CP_THREAD_ACP:
+            CodePage = CODEPAGE_SHIFT_JIS;
+            break;
+
+        default:
+            break;
+    }
+
+    return IsDBCSLeadByteEx_orig(CodePage, TestChar);
+}
+
 static
 int
 WINAPI
@@ -250,6 +274,18 @@ GetLocaleInfoA_hook(
 void hooks::lang::early_init() {
     log_info("hooks::lang", "early initialization");
 
+    const auto native_code_page = GetACP();
+    if (native_code_page == CP_UTF8) {
+        log_warning(
+            "hooks::lang",
+            "Windows is using UTF-8 as the system code page; "
+            "some games may render text incorrectly or behave unexpectedly");
+
+        deferredlogs::defer_error_messages({
+            "Windows is using UTF-8 as the system code page",
+            "    some games may render text incorrectly or behave unexpectedly"});
+    }
+
     // hooking these two functions fixes the jubeat mojibake
     detour::trampoline_try("kernel32.dll", "GetACP", GetACP_hook, &GetACP_orig);
     detour::trampoline_try("kernel32.dll", "GetOEMCP", GetOEMCP_hook, &GetOEMCP_orig);
@@ -315,6 +351,15 @@ void hooks::lang::early_init() {
             WideCharToMultiByte_hook,
             &WideCharToMultiByte_orig);
     }
+
+    if (games::popn::is_pikapika_model() && native_code_page == CP_UTF8) {
+        detour::trampoline_try(
+            "kernel32.dll",
+            "IsDBCSLeadByteEx",
+            IsDBCSLeadByteEx_hook,
+            &IsDBCSLeadByteEx_orig);
+    }
+
 #endif
 
 }