Show shutdown warning if there are multiple users logged in (#1303)

Author: ge0rdi

Src/StartMenu/StartMenuDLL/MenuCommands.cpp

@@ -836,6 +836,58 @@ static TOKEN_ELEVATION_TYPE GetCurrentTokenElevationType()
 return retval;
 }
 
+static BOOL WINAPI WinStationGetLoggedOnCount(ULONG* pUserSessions, ULONG* pDeviceSessions)
+{
+static auto p = static_cast<decltype(&WinStationGetLoggedOnCount)>((void*)GetProcAddress(GetModuleHandle(L"winsta.dll"), "WinStationGetLoggedOnCount"));
+if (p)
+return p(pUserSessions, pDeviceSessions);
+
+// fall-back
+return FALSE;
+}
+
+static bool ProceedWithShutdown(DWORD flags)
+{
+// this logic is inspired by user32!DisplayExitWindowsWarnings function (called from ExitWindowsEx)
+
+ULONG userSessions = 0;
+ULONG deviceSessions = 0;
+
+WinStationGetLoggedOnCount(&userSessions, &deviceSessions);
+
+// we can proceed if there is at most one user session and no device sessions
+if (userSessions <= 1 && deviceSessions == 0)
+return true;
+
+// otherwise inform user that somebody else is using the machine and ask for confirmation
+
+UINT msgId = 0;
+
+if (flags & SHUTDOWN_RESTART)
+{
+if (userSessions <= 1)
+msgId = 755;// One or more devices on your network are using the computer resources. Restarting Windows might cause them to lose data.
+else if (deviceSessions != 0)
+msgId = 756;// Other people and devices are using the computer resources. Restarting Windows might cause them to lose data.
+else
+msgId = 714;// Other people are logged on to this computer. Restarting Windows might cause them to lose data.
+}
+else
+{
+if (userSessions <= 1)
+msgId = 753;// One or more devices on your network are using the computer resources.Shutting down Windows might cause them to lose data.
+else if (deviceSessions != 0)
+msgId = 754;// Other people and devices are are using the computer resources. Shutting down Windows might cause them to lose data.
+else
+msgId = 713;// Other people are logged on to this computer. Shutting down Windows might cause them to lose data.
+}
+
+WCHAR message[MAX_PATH]{};
+LoadString(GetModuleHandle(L"user32.dll"), msgId, message, _countof(message));
+
+return MessageBox(NULL, message, L"Open-Shell", MB_YESNO | MB_ICONEXCLAMATION | MB_DEFBUTTON1 | MB_SYSTEMMODAL | MB_SETFOREGROUND | MB_SERVICE_NOTIFICATION) != IDNO;
+}
+
 static bool ExecuteShutdownCommand(TMenuID menuCommand)
 {
 DWORD flags = 0;
@@ -880,6 +932,11 @@ static bool ExecuteShutdownCommand(TMenuID menuCommand)
 
 if (flags)
 {
+if (!ProceedWithShutdown(flags))
+return true;
+
+flags |= SHUTDOWN_FORCE_OTHERS;
+
 if (SetShutdownPrivileges())
 {
 flags = WindowsUpdateAdjustShutdownFlags(flags);