text: // Copyright (c) 2014-2018 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #if defined(HAVE_CONFIG_H)
  #include <config/bitcoin-config.h>
  #endif
  
  #include <qt/winshutdownmonitor.h>
  
  #if defined(Q_OS_WIN)
  #include <shutdown.h>
  #include <util/system.h>
  
  #include <windows.h>
  
  #include <QDebug>
  
  #include <openssl/rand.h>
  
  // If we don't want a message to be processed by Qt, return true and set result to
  // the value that the window procedure should return. Otherwise return false.
  bool WinShutdownMonitor::nativeEventFilter(const QByteArray &eventType, void *pMessage, long *pnResult)
  {
         Q_UNUSED(eventType);
  
         MSG *pMsg = static_cast<MSG *>(pMessage);
  
         // Seed OpenSSL PRNG with Windows event data (e.g.  mouse movements and other user interactions)
         if (RAND_event(pMsg->message, pMsg->wParam, pMsg->lParam) == 0) {
              // Warn only once as this is performance-critical
              static bool warned = false;
              if (!warned) {
                  LogPrintf("%s: OpenSSL RAND_event() failed to seed OpenSSL PRNG with enough data.\n", __func__);
                  warned = true;
              }
         }
  
         switch(pMsg->message)
         {
             case WM_QUERYENDSESSION:
             {
                 // Initiate a client shutdown after receiving a WM_QUERYENDSESSION and block
                 // Windows session end until we have finished client shutdown.
                 StartShutdown();
                 *pnResult = FALSE;
                 return true;
             }
  
             case WM_ENDSESSION:
             {
                 *pnResult = FALSE;
                 return true;
             }
         }
  
         return false;
  }
  
  void WinShutdownMonitor::registerShutdownBlockReason(const QString& strReason, const HWND& mainWinId)
  {
      typedef BOOL (WINAPI *PSHUTDOWNBRCREATE)(HWND, LPCWSTR);
      PSHUTDOWNBRCREATE shutdownBRCreate = (PSHUTDOWNBRCREATE)GetProcAddress(GetModuleHandleA("User32.dll"), "ShutdownBlockReasonCreate");
      if (shutdownBRCreate == nullptr) {
          qWarning() << "registerShutdownBlockReason: GetProcAddress for ShutdownBlockReasonCreate failed";
          return;
      }
  
      if (shutdownBRCreate(mainWinId, strReason.toStdWString().c_str()))
          qWarning() << "registerShutdownBlockReason: Successfully registered: " + strReason;
      else
          qWarning() << "registerShutdownBlockReason: Failed to register: " + strReason;
  }
  #endif
  