From bdf39169c987b0ab5618c49cd0b74e531d00d6ce Mon Sep 17 00:00:00 2001
From: Yohei Yukawa <yukawa@chromium.org>
Date: Thu, 17 Oct 2024 13:16:35 -0700
Subject: [PATCH] Check registry

---
 src/base/system_util.cc | 44 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/src/base/system_util.cc b/src/base/system_util.cc
index ffb3cfa7a..012091970 100644
--- a/src/base/system_util.cc
+++ b/src/base/system_util.cc
@@ -409,11 +409,55 @@ class ProgramFilesX86Cache {
   HRESULT result_;
   std::string path_;
 };
+
+constexpr wchar_t kMozcTipClsid[] =
+    L"SOFTWARE\\Classes\\CLSID\\"
+#ifdef GOOGLE_JAPANESE_INPUT_BUILD
+    L"{D5A86FD5-5308-47EA-AD16-9C4EB160EC3C}"
+#else   // GOOGLE_JAPANESE_INPUT_BUILD
+    L"{10A67BC8-22FA-4A59-90DC-2546652C56BF}"
+#endif  // GOOGLE_JAPANESE_INPUT_BUILD
+    L"\\InprocServer32";
+
+std::string GetMozcInstallDirFromRegistry() {
+  // TSF requires the path of "mozc_tip64.dll" to be registered in the registry,
+  // which tells us Mozc's installation directory.
+  HKEY key = nullptr;
+  LSTATUS result =::RegOpenKeyExW(
+      HKEY_LOCAL_MACHINE, kMozcTipClsid, 0, KEY_READ | KEY_WOW64_64KEY, &key);
+  if (result != ERROR_SUCCESS) {
+    return "";
+  }
+
+  DWORD type = 0;
+  wchar_t buffer[MAX_PATH] = {};
+  DWORD buffer_size = sizeof(buffer);
+  result = ::RegQueryValueExW(
+      key, nullptr, nullptr, &type, reinterpret_cast<LPBYTE>(buffer),
+      &buffer_size);
+  ::RegCloseKey(key);
+  if (result != ERROR_SUCCESS || type != REG_SZ) {
+    return "";
+  }
+  const std::string tip64_path = win32::WideToUtf8(buffer);
+  if (tip64_path.empty()) {
+    return "";
+  }
+  if (!FileUtil::FileExists(tip64_path).ok()) {
+    return "";
+  }
+  return FileUtil::Dirname(tip64_path);
+}
+
 }  // namespace
 #endif  // _WIN32
 
 std::string SystemUtil::GetServerDirectory() {
 #ifdef _WIN32
+  const std::string install_dir_from_registry = GetMozcInstallDirFromRegistry();
+  if (!install_dir_from_registry.empty()) {
+    return install_dir_from_registry;
+  }
   DCHECK(SUCCEEDED(Singleton<ProgramFilesX86Cache>::get()->result()));
 #if defined(GOOGLE_JAPANESE_INPUT_BUILD)
   return FileUtil::JoinPath(