src/msw/dde.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        dde.cpp
   3 // Purpose:     DDE classes
   4 // Author:      Julian Smart
   5 // Modified by:
   6 // Created:     01/02/97
   7 // RCS-ID:      $Id$
   8 // Copyright:   (c) Julian Smart and Markus Holzem
   9 // Licence:     wxWindows licence
  10 /////////////////////////////////////////////////////////////////////////////
  11
  12 #ifdef __GNUG__
  13 #pragma implementation "dde.h"
  14 #endif
  15
  16 // For compilers that support precompilation, includes "wx.h".
  17 #include "wx/wxprec.h"
  18
  19 #ifdef __BORLANDC__
  20 #pragma hdrstop
  21 #endif
  22
  23 #ifndef WX_PRECOMP
  24 #include "wx/defs.h"
  25 #endif
  26
  27 #if wxUSE_IPC
  28
  29 #ifndef WX_PRECOMP
  30 #include "wx/utils.h"
  31 #include "wx/app.h"
  32 #endif
  33
  34 #include "wx/msw/private.h"
  35 #include "wx/dde.h"
  36
  37 #ifndef __TWIN32__
  38 #ifdef __GNUWIN32__
  39 #include "wx/msw/gnuwin32/extra.h"
  40 #endif
  41 #endif
  42
  43 #include <windows.h>
  44 #include <ddeml.h>
  45 #include <string.h>
  46
  47 #ifdef __WIN32__
  48 #define _EXPORT /**/
  49 #else
  50 #define _EXPORT _export
  51 #endif
  52
  53 #if !USE_SHARED_LIBRARY
  54 IMPLEMENT_DYNAMIC_CLASS(wxDDEServer, wxServerBase)
  55 IMPLEMENT_DYNAMIC_CLASS(wxDDEClient, wxClientBase)
  56 IMPLEMENT_CLASS(wxDDEConnection, wxConnectionBase)
  57 #endif
  58
  59 static wxDDEConnection *DDEFindConnection(HCONV hConv);
  60 static void DDEDeleteConnection(HCONV hConv);
  61 static wxDDEServer *DDEFindServer(const wxString& s);
  62
  63 extern "C" HDDEDATA EXPENTRY _EXPORT _DDECallback(
  64 WORD wType,
  65 WORD wFmt,
  66 HCONV hConv,
  67 HSZ hsz1,
  68 HSZ hsz2,
  69 HDDEDATA hData,
  70 DWORD lData1,
  71 DWORD lData2);
  72
  73 // Add topic name to atom table before using in conversations
  74 static HSZ DDEAddAtom(const wxString& string);
  75 static HSZ DDEGetAtom(const wxString& string);
  76 static void DDEPrintError(void);
  77
  78 static DWORD DDEIdInst = 0L;
  79 static wxDDEConnection *DDECurrentlyConnecting = NULL;
  80
  81 static wxList wxAtomTable(wxKEY_STRING);
  82 static wxList wxDDEClientObjects;
  83 static wxList wxDDEServerObjects;
  84
  85 char *DDEDefaultIPCBuffer = NULL;
  86 int DDEDefaultIPCBufferSize = 0;
  87
  88 /*
  89  * Initialization
  90  *
  91  */
  92
  93 static bool DDEInitialized = FALSE;
  94
  95 void wxDDEInitialize()
  96 {
  97   if (DDEInitialized)
  98     return;
  99   DDEInitialized = TRUE;
 100
 101   // Should insert filter flags
 102   DdeInitialize(&DDEIdInst, (PFNCALLBACK)MakeProcInstance(
 103                (FARPROC)_DDECallback, wxGetInstance()),
 104                APPCLASS_STANDARD,
 105                0L);
 106 }
 107
 108 /*
 109  * CleanUp
 110  */
 111
 112 void wxDDECleanUp()
 113 {
 114   if (DDEIdInst != 0)
 115   {
 116     DdeUninitialize(DDEIdInst);
 117     DDEIdInst = 0;
 118   }
 119   if (DDEDefaultIPCBuffer)
 120     delete [] DDEDefaultIPCBuffer ;
 121 }
 122
 123 // Global find connection
 124 static wxDDEConnection *DDEFindConnection(HCONV hConv)
 125 {
 126   wxNode *node = wxDDEServerObjects.First();
 127   wxDDEConnection *found = NULL;
 128   while (node && !found)
 129   {
 130     wxDDEServer *object = (wxDDEServer *)node->Data();
 131     found = object->FindConnection((WXHCONV) hConv);
 132     node = node->Next();
 133   }
 134   if (found)
 135         return found;
 136
 137   node = wxDDEClientObjects.First();
 138   while (node && !found)
 139   {
 140     wxDDEClient *object = (wxDDEClient *)node->Data();
 141     found = object->FindConnection((WXHCONV) hConv);
 142     node = node->Next();
 143   }
 144   return found;
 145 }
 146
 147 // Global delete connection
 148 static void DDEDeleteConnection(HCONV hConv)
 149 {
 150   wxNode *node = wxDDEServerObjects.First();
 151   bool found = FALSE;
 152   while (node && !found)
 153   {
 154     wxDDEServer *object = (wxDDEServer *)node->Data();
 155     found = object->DeleteConnection((WXHCONV) hConv);
 156     node = node->Next();
 157   }
 158   if (found)
 159         return;
 160
 161   node = wxDDEServerObjects.First();
 162   while (node && !found)
 163   {
 164     wxDDEClient *object = (wxDDEClient *)node->Data();
 165     found = object->DeleteConnection((WXHCONV) hConv);
 166     node = node->Next();
 167   }
 168 }
 169
 170 // Find a server from a service name
 171 static wxDDEServer *DDEFindServer(const wxString& s)
 172 {
 173   wxNode *node = wxDDEServerObjects.First();
 174   wxDDEServer *found = NULL;
 175   while (node && !found)
 176   {
 177     wxDDEServer *object = (wxDDEServer *)node->Data();
 178
 179     if (object->GetServiceName() == s)
 180       found = object;
 181     else node = node->Next();
 182   }
 183   return found;
 184 }
 185
 186 /*
 187  * Server
 188  *
 189  */
 190
 191 wxDDEServer::wxDDEServer(void)
 192 {
 193   m_serviceName = "";
 194   wxDDEServerObjects.Append(this);
 195 }
 196
 197 bool wxDDEServer::Create(const wxString& server_name)
 198 {
 199   m_serviceName = server_name;
 200   HSZ serviceName = DdeCreateStringHandle(DDEIdInst, (char*) (const char *)server_name, CP_WINANSI);
 201
 202   if (DdeNameService(DDEIdInst, serviceName, (HSZ) NULL, DNS_REGISTER) == 0)
 203   {
 204     DDEPrintError();
 205     return FALSE;
 206   }
 207   return TRUE;
 208 }
 209
 210 wxDDEServer::~wxDDEServer(void)
 211 {
 212   if (m_serviceName != "")
 213   {
 214     HSZ serviceName = DdeCreateStringHandle(DDEIdInst, (char*) (const char *)m_serviceName, CP_WINANSI);
 215     if (DdeNameService(DDEIdInst, serviceName, NULL, DNS_UNREGISTER) == 0)
 216     {
 217       DDEPrintError();
 218     }
 219   }
 220   wxDDEServerObjects.DeleteObject(this);
 221
 222   wxNode *node = m_connections.First();
 223   while (node)
 224   {
 225     wxDDEConnection *connection = (wxDDEConnection *)node->Data();
 226     wxNode *next = node->Next();
 227     connection->OnDisconnect(); // May delete the node implicitly
 228     node = next;
 229   }
 230
 231   // If any left after this, delete them
 232   node = m_connections.First();
 233   while (node)
 234   {
 235     wxDDEConnection *connection = (wxDDEConnection *)node->Data();
 236     wxNode *next = node->Next();
 237     delete connection;
 238     node = next;
 239   }
 240 }
 241
 242 wxConnectionBase *wxDDEServer::OnAcceptConnection(const wxString& /* topic */)
 243 {
 244         return new wxDDEConnection;
 245 }
 246
 247 wxDDEConnection *wxDDEServer::FindConnection(WXHCONV conv)
 248 {
 249   wxNode *node = m_connections.First();
 250   wxDDEConnection *found = NULL;
 251   while (node && !found)
 252   {
 253     wxDDEConnection *connection = (wxDDEConnection *)node->Data();
 254     if (connection->m_hConv == conv)
 255       found = connection;
 256     else node = node->Next();
 257   }
 258   return found;
 259 }
 260
 261 // Only delete the entry in the map, not the actual connection
 262 bool wxDDEServer::DeleteConnection(WXHCONV conv)
 263 {
 264   wxNode *node = m_connections.First();
 265   bool found = FALSE;
 266   while (node && !found)
 267   {
 268     wxDDEConnection *connection = (wxDDEConnection *)node->Data();
 269     if (connection->m_hConv == conv)
 270     {
 271       found = TRUE;
 272       delete node;
 273     }
 274     else node = node->Next();
 275   }
 276   return found;
 277 }
 278
 279
 280 /*
 281  * Client
 282  *
 283  */
 284
 285
 286 wxDDEClient::wxDDEClient(void)
 287 {
 288   wxDDEClientObjects.Append(this);
 289 }
 290
 291 wxDDEClient::~wxDDEClient(void)
 292 {
 293   wxDDEClientObjects.DeleteObject(this);
 294   wxNode *node = m_connections.First();
 295   while (node)
 296   {
 297     wxDDEConnection *connection = (wxDDEConnection *)node->Data();
 298     delete connection;  // Deletes the node implicitly (see ~wxDDEConnection)
 299     node = m_connections.First();
 300   }
 301 }
 302
 303 bool wxDDEClient::ValidHost(const wxString& /* host */)
 304 {
 305   return TRUE;
 306 }
 307
 308 wxConnectionBase *wxDDEClient::MakeConnection(const wxString& /* host */, const wxString& server_name, const wxString& topic)
 309 {
 310   HSZ serviceName = DdeCreateStringHandle(DDEIdInst, (char*) (const char *)server_name, CP_WINANSI);
 311   HSZ topic_atom = DdeCreateStringHandle(DDEIdInst, (char*) (const char *)topic, CP_WINANSI);
 312
 313   HCONV hConv = DdeConnect(DDEIdInst, serviceName, topic_atom, (PCONVCONTEXT)NULL);
 314   if (hConv == (HCONV) NULL)
 315     return (wxConnectionBase*) NULL;
 316   else
 317   {
 318     wxDDEConnection *connection = (wxDDEConnection*) OnMakeConnection();
 319     if (connection)
 320     {
 321       connection->m_hConv = (WXHCONV) hConv;
 322       connection->m_topicName = topic;
 323           connection->m_client = this;
 324       m_connections.Append(connection);
 325       return connection;
 326     }
 327     else return (wxConnectionBase*) NULL;
 328   }
 329 }
 330
 331 wxConnectionBase *wxDDEClient::OnMakeConnection(void)
 332 {
 333         return new wxDDEConnection;
 334 }
 335
 336 wxDDEConnection *wxDDEClient::FindConnection(WXHCONV conv)
 337 {
 338   wxNode *node = m_connections.First();
 339   wxDDEConnection *found = NULL;
 340   while (node && !found)
 341   {
 342     wxDDEConnection *connection = (wxDDEConnection *)node->Data();
 343     if (connection->m_hConv == conv)
 344       found = connection;
 345     else node = node->Next();
 346   }
 347   return found;
 348 }
 349
 350 // Only delete the entry in the map, not the actual connection
 351 bool wxDDEClient::DeleteConnection(WXHCONV conv)
 352 {
 353   wxNode *node = m_connections.First();
 354   bool found = FALSE;
 355   while (node && !found)
 356   {
 357     wxDDEConnection *connection = (wxDDEConnection *)node->Data();
 358     if (connection->m_hConv == conv)
 359     {
 360       found = TRUE;
 361       delete node;
 362     }
 363     else node = node->Next();
 364   }
 365   return found;
 366 }
 367
 368 /*
 369  * Connection
 370  */
 371
 372 wxDDEConnection::wxDDEConnection(char *buffer, int size)
 373 {
 374   if (buffer == NULL)
 375   {
 376     if (DDEDefaultIPCBuffer == NULL)
 377       DDEDefaultIPCBuffer = new char[DDEDefaultIPCBufferSize];
 378     m_bufPtr = DDEDefaultIPCBuffer;
 379     m_bufSize = DDEDefaultIPCBufferSize;
 380   }
 381   else
 382   {
 383     m_bufPtr = buffer;
 384     m_bufSize = size;
 385   }
 386
 387   m_topicName = "";
 388
 389   m_client = NULL;
 390   m_server = NULL;
 391
 392   m_hConv = 0;
 393   m_sendingData = NULL;
 394 }
 395
 396 wxDDEConnection::wxDDEConnection(void)
 397 {
 398   m_hConv = 0;
 399   m_sendingData = NULL;
 400   m_server = NULL;
 401   m_client = NULL;
 402   if (DDEDefaultIPCBuffer == NULL)
 403     DDEDefaultIPCBuffer = new char[DDEDefaultIPCBufferSize];
 404
 405   m_bufPtr = DDEDefaultIPCBuffer;
 406   m_bufSize = DDEDefaultIPCBufferSize;
 407   m_topicName = "";
 408 }
 409
 410 wxDDEConnection::~wxDDEConnection(void)
 411 {
 412         if (m_server)
 413                 m_server->GetConnections().DeleteObject(this);
 414         else
 415             m_client->GetConnections().DeleteObject(this);
 416 }
 417
 418 // Calls that CLIENT can make
 419 bool wxDDEConnection::Disconnect(void)
 420 {
 421   DDEDeleteConnection((HCONV) m_hConv);
 422   return (DdeDisconnect((HCONV) m_hConv) != 0);
 423 }
 424
 425 bool wxDDEConnection::Execute(char *data, int size, wxIPCFormat format)
 426 {
 427   DWORD result;
 428   if (size < 0)
 429     size = strlen(data);
 430
 431   size ++;
 432
 433   return (DdeClientTransaction((LPBYTE)data, size, (HCONV) m_hConv,
 434     NULL, format, XTYP_EXECUTE, 5000, &result) ? TRUE : FALSE);
 435 }
 436
 437 char *wxDDEConnection::Request(const wxString& item, int *size, wxIPCFormat format)
 438 {
 439   DWORD result;
 440   HSZ atom = DDEGetAtom(item);
 441
 442   HDDEDATA returned_data = DdeClientTransaction(NULL, 0, (HCONV) m_hConv,
 443     atom, format, XTYP_REQUEST, 5000, &result);
 444
 445   DWORD len = DdeGetData(returned_data, (LPBYTE)(m_bufPtr), m_bufSize, 0);
 446
 447   DdeFreeDataHandle(returned_data);
 448
 449   if (size) *size = (int)len;
 450   if (len > 0)
 451   {
 452     return m_bufPtr;
 453   }
 454   else return NULL;
 455 }
 456
 457 bool wxDDEConnection::Poke(const wxString& item, char *data, int size, wxIPCFormat format)
 458 {
 459   DWORD result;
 460   if (size < 0)
 461     size = strlen(data);
 462
 463   size ++;
 464
 465   HSZ item_atom = DDEGetAtom(item);
 466   return (DdeClientTransaction((LPBYTE)data, size, (HCONV) m_hConv,
 467     item_atom, format, XTYP_POKE, 5000, &result) ? TRUE : FALSE);
 468 }
 469
 470 bool wxDDEConnection::StartAdvise(const wxString& item)
 471 {
 472   DWORD result;
 473   HSZ atom = DDEGetAtom(item);
 474
 475   return (DdeClientTransaction(NULL, 0, (HCONV) m_hConv,
 476     atom, CF_TEXT, XTYP_ADVSTART, 5000, &result) ? TRUE : FALSE);
 477 }
 478
 479 bool wxDDEConnection::StopAdvise(const wxString& item)
 480 {
 481   DWORD result;
 482   HSZ atom = DDEGetAtom(item);
 483
 484   return (DdeClientTransaction(NULL, 0, (HCONV) m_hConv,
 485     atom, CF_TEXT, XTYP_ADVSTOP, 5000, &result) ? TRUE : FALSE);
 486 }
 487
 488 // Calls that SERVER can make
 489 bool wxDDEConnection::Advise(const wxString& item, char *data, int size, wxIPCFormat format)
 490 {
 491   if (size < 0)
 492     size = strlen(data);
 493
 494   size ++;
 495
 496   HSZ item_atom = DDEGetAtom(item);
 497   HSZ topic_atom = DDEGetAtom(m_topicName);
 498   m_sendingData = data;
 499   m_dataSize = size;
 500   m_dataType = format;
 501   return (DdePostAdvise(DDEIdInst, topic_atom, item_atom) != 0);
 502 }
 503
 504 bool wxDDEConnection::OnDisconnect(void)
 505 {
 506         delete this;
 507         return TRUE;
 508 }
 509
 510
 511 #define DDERETURN HDDEDATA
 512
 513 HDDEDATA EXPENTRY _EXPORT _DDECallback(
 514 WORD wType,
 515 WORD wFmt,
 516 HCONV hConv,
 517 HSZ hsz1,
 518 HSZ hsz2,
 519 HDDEDATA hData,
 520 DWORD /* lData1 */,
 521 DWORD /* lData2 */)
 522 {
 523   switch (wType)
 524   {
 525     case XTYP_CONNECT:
 526     {
 527       char topic_buf[100];
 528       char server_buf[100];
 529       DdeQueryString(DDEIdInst, hsz1, (LPSTR)topic_buf, sizeof(topic_buf),
 530                      CP_WINANSI);
 531       DdeQueryString(DDEIdInst, hsz2, (LPSTR)server_buf, sizeof(topic_buf),
 532                      CP_WINANSI);
 533       wxDDEServer *server = DDEFindServer(server_buf);
 534       if (server)
 535       {
 536         wxDDEConnection *connection =
 537           (wxDDEConnection*) server->OnAcceptConnection(wxString(topic_buf));
 538         if (connection)
 539         {
 540           connection->m_server = server;
 541           server->GetConnections().Append(connection);
 542           connection->m_hConv = 0;
 543           connection->m_topicName = topic_buf;
 544           DDECurrentlyConnecting = connection;
 545           return (DDERETURN)TRUE;
 546         }
 547       }
 548       else return (DDERETURN)0;
 549       break;
 550     }
 551
 552     case XTYP_CONNECT_CONFIRM:
 553     {
 554       if (DDECurrentlyConnecting)
 555       {
 556         DDECurrentlyConnecting->m_hConv = (WXHCONV) hConv;
 557         DDECurrentlyConnecting = NULL;
 558         return (DDERETURN)TRUE;
 559       }
 560       else return 0;
 561       break;
 562     }
 563
 564     case XTYP_DISCONNECT:
 565     {
 566       wxDDEConnection *connection = DDEFindConnection(hConv);
 567       if (connection && connection->OnDisconnect())
 568       {
 569         DDEDeleteConnection(hConv);  // Delete mapping: hConv => connection
 570         return (DDERETURN)TRUE;
 571       }
 572       else return (DDERETURN)0;
 573       break;
 574     }
 575
 576     case XTYP_EXECUTE:
 577     {
 578       wxDDEConnection *connection = DDEFindConnection(hConv);
 579
 580       if (connection)
 581       {
 582         DWORD len = DdeGetData(hData, (LPBYTE)(connection->m_bufPtr), connection->m_bufSize, 0);
 583         DdeFreeDataHandle(hData);
 584         if (connection->OnExecute(connection->m_topicName, connection->m_bufPtr, (int)len, (wxIPCFormat) wFmt))
 585           return (DDERETURN)DDE_FACK;
 586         else
 587           return (DDERETURN)DDE_FNOTPROCESSED;
 588       } else return (DDERETURN)DDE_FNOTPROCESSED;
 589       break;
 590     }
 591
 592     case XTYP_REQUEST:
 593     {
 594       wxDDEConnection *connection = DDEFindConnection(hConv);
 595
 596       if (connection)
 597       {
 598         char item_name[200];
 599         DdeQueryString(DDEIdInst, hsz2, (LPSTR)item_name, sizeof(item_name),
 600                      CP_WINANSI);
 601
 602         int user_size = -1;
 603         char *data = connection->OnRequest(connection->m_topicName, wxString(item_name), &user_size, (wxIPCFormat) wFmt);
 604         if (data)
 605         {
 606           if (user_size < 0) user_size = strlen(data);
 607
 608           HDDEDATA handle = DdeCreateDataHandle(DDEIdInst,
 609                  (LPBYTE)data, user_size + 1, 0, hsz2, wFmt, 0);
 610           return (DDERETURN)handle;
 611         } else return (DDERETURN)0;
 612       } else return (DDERETURN)0;
 613       break;
 614     }
 615
 616     case XTYP_POKE:
 617     {
 618       wxDDEConnection *connection = DDEFindConnection(hConv);
 619
 620       if (connection)
 621       {
 622         char item_name[200];
 623         DdeQueryString(DDEIdInst, hsz2, (LPSTR)item_name, sizeof(item_name),
 624                      CP_WINANSI);
 625         DWORD len = DdeGetData(hData, (LPBYTE)(connection->m_bufPtr), connection->m_bufSize, 0);
 626         DdeFreeDataHandle(hData);
 627         connection->OnPoke(connection->m_topicName, wxString(item_name), connection->m_bufPtr, (int)len, (wxIPCFormat) wFmt);
 628         return (DDERETURN)DDE_FACK;
 629       } else return (DDERETURN)DDE_FNOTPROCESSED;
 630       break;
 631     }
 632
 633     case XTYP_ADVSTART:
 634     {
 635       wxDDEConnection *connection = DDEFindConnection(hConv);
 636
 637       if (connection)
 638       {
 639         char item_name[200];
 640         DdeQueryString(DDEIdInst, hsz2, (LPSTR)item_name, sizeof(item_name),
 641                      CP_WINANSI);
 642
 643         return (DDERETURN)connection->OnStartAdvise(connection->m_topicName, wxString(item_name));
 644       } else return (DDERETURN)0;
 645       break;
 646     }
 647
 648     case XTYP_ADVSTOP:
 649     {
 650       wxDDEConnection *connection = DDEFindConnection(hConv);
 651
 652       if (connection)
 653       {
 654         char item_name[200];
 655         DdeQueryString(DDEIdInst, hsz2, (LPSTR)item_name, sizeof(item_name),
 656                      CP_WINANSI);
 657         return (DDERETURN)connection->OnStopAdvise(connection->m_topicName, wxString(item_name));
 658       } else return (DDERETURN)0;
 659       break;
 660     }
 661
 662     case XTYP_ADVREQ:
 663     {
 664       wxDDEConnection *connection = DDEFindConnection(hConv);
 665
 666       if (connection && connection->m_sendingData)
 667       {
 668         HDDEDATA data = DdeCreateDataHandle(DDEIdInst,
 669                           (LPBYTE)connection->m_sendingData,
 670                           connection->m_dataSize, 0, hsz2, connection->m_dataType, 0);
 671         connection->m_sendingData = NULL;
 672         return (DDERETURN)data;
 673       } else return (DDERETURN)NULL;
 674       break;
 675     }
 676
 677     case XTYP_ADVDATA:
 678     {
 679       wxDDEConnection *connection = DDEFindConnection(hConv);
 680
 681       if (connection)
 682       {
 683         char item_name[200];
 684         DdeQueryString(DDEIdInst, hsz2, (LPSTR)item_name, sizeof(item_name),
 685                      CP_WINANSI);
 686
 687         DWORD len = DdeGetData(hData, (LPBYTE)(connection->m_bufPtr), connection->m_bufSize, 0);
 688         DdeFreeDataHandle(hData);
 689         if (connection->OnAdvise(connection->m_topicName, wxString(item_name), connection->m_bufPtr, (int)len, (wxIPCFormat) wFmt))
 690           return (DDERETURN)DDE_FACK;
 691         else
 692           return (DDERETURN)DDE_FNOTPROCESSED;
 693       } else return (DDERETURN)DDE_FNOTPROCESSED;
 694       break;
 695     }
 696   }
 697   return 0;
 698 }
 699
 700 // Atom table stuff
 701 static HSZ DDEAddAtom(const wxString& string)
 702 {
 703   HSZ atom = DdeCreateStringHandle(DDEIdInst, (char*) (const char *)string, CP_WINANSI);
 704   wxAtomTable.Append(string, (wxObject *)atom);
 705   return atom;
 706 }
 707
 708 static HSZ DDEGetAtom(const wxString& string)
 709 {
 710   wxNode *node = wxAtomTable.Find(string);
 711   if (node)
 712     return (HSZ)node->Data();
 713   else
 714   {
 715     DDEAddAtom(string);
 716     return (HSZ)(wxAtomTable.Find(string)->Data());
 717   }
 718 }
 719
 720 void DDEPrintError(void)
 721 {
 722   char *err = NULL;
 723   switch (DdeGetLastError(DDEIdInst))
 724   {
 725     case DMLERR_ADVACKTIMEOUT:
 726       err = "A request for a synchronous advise transaction has timed out.";
 727       break;
 728     case DMLERR_BUSY:
 729       err = "The response to the transaction caused the DDE_FBUSY bit to be set.";
 730       break;
 731     case DMLERR_DATAACKTIMEOUT:
 732       err = "A request for a synchronous data transaction has timed out.";
 733       break;
 734     case DMLERR_DLL_NOT_INITIALIZED:
 735       err = "A DDEML function was called without first calling the DdeInitialize function,\n\ror an invalid instance identifier\n\rwas passed to a DDEML function.";
 736       break;
 737     case DMLERR_DLL_USAGE:
 738       err = "An application initialized as APPCLASS_MONITOR has\n\rattempted to perform a DDE transaction,\n\ror an application initialized as APPCMD_CLIENTONLY has \n\rattempted to perform server transactions.";
 739       break;
 740     case DMLERR_EXECACKTIMEOUT:
 741       err = "A request for a synchronous execute transaction has timed out.";
 742       break;
 743     case DMLERR_INVALIDPARAMETER:
 744       err = "A parameter failed to be validated by the DDEML.";
 745       break;
 746     case DMLERR_LOW_MEMORY:
 747       err = "A DDEML application has created a prolonged race condition.";
 748       break;
 749     case DMLERR_MEMORY_ERROR:
 750       err = "A memory allocation failed.";
 751       break;
 752     case DMLERR_NO_CONV_ESTABLISHED:
 753       err = "A client's attempt to establish a conversation has failed.";
 754       break;
 755     case DMLERR_NOTPROCESSED:
 756       err = "A transaction failed.";
 757       break;
 758     case DMLERR_POKEACKTIMEOUT:
 759       err = "A request for a synchronous poke transaction has timed out.";
 760       break;
 761     case DMLERR_POSTMSG_FAILED:
 762       err = "An internal call to the PostMessage function has failed. ";
 763       break;
 764     case DMLERR_REENTRANCY:
 765       err = "Reentrancy problem.";
 766       break;
 767     case DMLERR_SERVER_DIED:
 768       err = "A server-side transaction was attempted on a conversation\n\rthat was terminated by the client, or the server\n\rterminated before completing a transaction.";
 769       break;
 770     case DMLERR_SYS_ERROR:
 771       err = "An internal error has occurred in the DDEML.";
 772       break;
 773     case DMLERR_UNADVACKTIMEOUT:
 774       err = "A request to end an advise transaction has timed out.";
 775       break;
 776     case DMLERR_UNFOUND_QUEUE_ID:
 777       err = "An invalid transaction identifier was passed to a DDEML function.\n\rOnce the application has returned from an XTYP_XACT_COMPLETE callback,\n\rthe transaction identifier for that callback is no longer valid.";
 778       break;
 779     default:
 780       err = "Unrecognised error type.";
 781       break;
 782   }
 783   MessageBox((HWND) NULL, (LPCSTR)err, "DDE Error", MB_OK | MB_ICONINFORMATION);
 784 }
 785
 786 #endif
 787   // wxUSE_IPC