title: Delphi program don't have error but don't show the result of callback function
body: <p>I want to convert c++ code to Delphi. The c++ code is getting stream from camera(Hikvision).I use a dll in my program, I am using this function in dll:  </p>
  
  <p><strong>c++ code:</strong>  </p>
  
  <pre><code>NET_DVR_API LONG __stdcall NET_DVR_RealPlay_V30(LONG lUserID, LPNET_DVR_CLIENTINFO lpClientInfo, void(CALLBACK *fRealDataCallBack_V30) (LONG lRealHandle, DWORD dwDataType, BYTE *pBuffer, DWORD dwBufSize, void* pUser) = NULL, void* pUser = NULL, BOOL bBlocked = FALSE);  
  </code></pre>
  
  <p><strong>delphi code (that I convert):</strong>  </p>
  
  <pre><code>type
  fRealDataCallBack_V30 =procedure(lRealHandle : LongInt; dwDataType: DWORD;pBuffer: PByte; dwBufSize: DWORD; dwUser: DWORD);stdcall;
  function  NET_DVR_RealPlay_V30 ( lUserID: Longint; lpClientInfo: LPNET_DVR_CLIENTINFO; fRealDataCallBack_V30: fRealDataCallBack_V30; pUser: Pointer; bBlocked: Boolean): Longint;stdcall; external 'HCNetSDK.dll'name 'NET_DVR_RealPlay_V30';
  </code></pre>
  
  <p>That function needs callback function:<br>
  <strong>c++ code :</strong>  </p>
  
  <pre><code> void CALLBACK fRealDataCallBack(LONG lRealHandle, DWORD dwDataType, BYTE *pBuffer, DWORD dwBufSize, void* dwUser)
      {
          printf("\nhello");
      }
  </code></pre>
  
  <p><strong>Delphi code(that I convert):</strong>  </p>
  
  <pre><code>procedure RealDataCallBack(lRealHandle: Longint; dwDataType: Longword; pBuffer: LPByte; dwBufSize: Longword; pUser:Pointer);stdcall;
  begin
   ShowMessage('hello');
  end;
  </code></pre>
  
  <p>and use that callback function as a parameter in dll function:  </p>
  
  <p><strong>c++ code:</strong>  </p>
  
  <pre><code>NET_DVR_RealPlay_V30(lUserID,&amp;client, fRealDataCallBack,NULL,false);  
  </code></pre>
  
  <p><strong>delphi code (that I convert):</strong>  </p>
  
  <pre><code>NET_DVR_RealPlay_V30(iLoginID,@lpClientInfo,RealDataCallBack,nil,false);
  </code></pre>
  
  <p>my c++ code is work completely correctly,but my delphi code can't call callback function.</p>