src/msw/thread.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        thread.cpp
   3 // Purpose:     wxThread Implementation
   4 // Author:      Original from Wolfram Gloger/Guilhem Lavaux
   5 // Modified by: Vadim Zeitlin to make it work :-)
   6 // Created:     04/22/98
   7 // RCS-ID:      $Id$
   8 // Copyright:   (c) Wolfram Gloger (1996, 1997); Guilhem Lavaux (1998),
   9 //                  Vadim Zeitlin (1999)
  10 // Licence:     wxWindows licence
  11 /////////////////////////////////////////////////////////////////////////////
  12
  13 #ifdef __GNUG__
  14     #pragma implementation "thread.h"
  15 #endif
  16
  17 // ----------------------------------------------------------------------------
  18 // headers
  19 // ----------------------------------------------------------------------------
  20
  21 // For compilers that support precompilation, includes "wx.h".
  22 #include "wx/wxprec.h"
  23
  24 #if defined(__BORLANDC__)
  25     #pragma hdrstop
  26 #endif
  27
  28 #ifndef WX_PRECOMP
  29     #include "wx/wx.h"
  30 #endif
  31
  32 #if wxUSE_THREADS
  33
  34 #include <stdio.h>
  35
  36 #include <windows.h>
  37
  38 #include "wx/module.h"
  39 #include "wx/thread.h"
  40
  41 // the possible states of the thread ("=>" shows all possible transitions from
  42 // this state)
  43 enum wxThreadState
  44 {
  45     STATE_NEW,          // didn't start execution yet (=> RUNNING)
  46     STATE_RUNNING,      // thread is running (=> PAUSED, CANCELED)
  47     STATE_PAUSED,       // thread is temporarily suspended (=> RUNNING)
  48     STATE_CANCELED,     // thread should terminate a.s.a.p. (=> EXITED)
  49     STATE_EXITED        // thread is terminating
  50 };
  51
  52 // ----------------------------------------------------------------------------
  53 // static variables
  54 // ----------------------------------------------------------------------------
  55
  56 // TLS index of the slot where we store the pointer to the current thread
  57 static DWORD s_tlsThisThread = 0xFFFFFFFF;
  58
  59 // id of the main thread - the one which can call GUI functions without first
  60 // calling wxMutexGuiEnter()
  61 static DWORD s_idMainThread = 0;
  62
  63 // if it's FALSE, some secondary thread is holding the GUI lock
  64 static bool s_bGuiOwnedByMainThread = TRUE;
  65
  66 // critical section which controls access to all GUI functions: any secondary
  67 // thread (i.e. except the main one) must enter this crit section before doing
  68 // any GUI calls
  69 static wxCriticalSection *s_critsectGui = NULL;
  70
  71 // critical section which protects s_nWaitingForGui variable
  72 static wxCriticalSection *s_critsectWaitingForGui = NULL;
  73
  74 // number of threads waiting for GUI in wxMutexGuiEnter()
  75 static size_t s_nWaitingForGui = 0;
  76
  77 // are we waiting for a thread termination?
  78 static bool s_waitingForThread = FALSE;
  79
  80 // ============================================================================
  81 // Windows implementation of thread classes
  82 // ============================================================================
  83
  84 // ----------------------------------------------------------------------------
  85 // wxMutex implementation
  86 // ----------------------------------------------------------------------------
  87 class wxMutexInternal
  88 {
  89 public:
  90     HANDLE p_mutex;
  91 };
  92
  93 wxMutex::wxMutex()
  94 {
  95     p_internal = new wxMutexInternal;
  96     p_internal->p_mutex = CreateMutex(NULL, FALSE, NULL);
  97     if ( !p_internal->p_mutex )
  98     {
  99         wxLogSysError(_("Can not create mutex."));
 100     }
 101
 102     m_locked = 0;
 103 }
 104
 105 wxMutex::~wxMutex()
 106 {
 107     if (m_locked > 0)
 108         wxLogDebug("Warning: freeing a locked mutex (%d locks).", m_locked);
 109     CloseHandle(p_internal->p_mutex);
 110 }
 111
 112 wxMutexError wxMutex::Lock()
 113 {
 114     DWORD ret;
 115
 116     ret = WaitForSingleObject(p_internal->p_mutex, INFINITE);
 117     switch ( ret )
 118     {
 119         case WAIT_ABANDONED:
 120             return wxMUTEX_BUSY;
 121
 122         case WAIT_OBJECT_0:
 123             // ok
 124             break;
 125
 126         case WAIT_FAILED:
 127             wxLogSysError(_("Couldn't acquire a mutex lock"));
 128             return wxMUTEX_MISC_ERROR;
 129
 130         case WAIT_TIMEOUT:
 131         default:
 132             wxFAIL_MSG("impossible return value in wxMutex::Lock");
 133     }
 134
 135     m_locked++;
 136     return wxMUTEX_NO_ERROR;
 137 }
 138
 139 wxMutexError wxMutex::TryLock()
 140 {
 141     DWORD ret;
 142
 143     ret = WaitForSingleObject(p_internal->p_mutex, 0);
 144     if (ret == WAIT_TIMEOUT || ret == WAIT_ABANDONED)
 145         return wxMUTEX_BUSY;
 146
 147     m_locked++;
 148     return wxMUTEX_NO_ERROR;
 149 }
 150
 151 wxMutexError wxMutex::Unlock()
 152 {
 153     if (m_locked > 0)
 154         m_locked--;
 155
 156     BOOL ret = ReleaseMutex(p_internal->p_mutex);
 157     if ( ret == 0 )
 158     {
 159         wxLogSysError(_("Couldn't release a mutex"));
 160         return wxMUTEX_MISC_ERROR;
 161     }
 162
 163     return wxMUTEX_NO_ERROR;
 164 }
 165
 166 // ----------------------------------------------------------------------------
 167 // wxCondition implementation
 168 // ----------------------------------------------------------------------------
 169
 170 class wxConditionInternal
 171 {
 172 public:
 173     HANDLE event;
 174     int waiters;
 175 };
 176
 177 wxCondition::wxCondition()
 178 {
 179     p_internal = new wxConditionInternal;
 180     p_internal->event = CreateEvent(NULL, FALSE, FALSE, NULL);
 181     if ( !p_internal->event )
 182     {
 183         wxLogSysError(_("Can not create event object."));
 184     }
 185
 186     p_internal->waiters = 0;
 187 }
 188
 189 wxCondition::~wxCondition()
 190 {
 191     CloseHandle(p_internal->event);
 192 }
 193
 194 void wxCondition::Wait(wxMutex& mutex)
 195 {
 196     mutex.Unlock();
 197     p_internal->waiters++;
 198     WaitForSingleObject(p_internal->event, INFINITE);
 199     p_internal->waiters--;
 200     mutex.Lock();
 201 }
 202
 203 bool wxCondition::Wait(wxMutex& mutex,
 204                        unsigned long sec,
 205                        unsigned long nsec)
 206 {
 207     DWORD ret;
 208
 209     mutex.Unlock();
 210     p_internal->waiters++;
 211     ret = WaitForSingleObject(p_internal->event, (sec*1000)+(nsec/1000000));
 212     p_internal->waiters--;
 213     mutex.Lock();
 214
 215     return (ret != WAIT_TIMEOUT);
 216 }
 217
 218 void wxCondition::Signal()
 219 {
 220     SetEvent(p_internal->event);
 221 }
 222
 223 void wxCondition::Broadcast()
 224 {
 225     int i;
 226
 227     for (i=0;i<p_internal->waiters;i++)
 228     {
 229         if ( SetEvent(p_internal->event) == 0 )
 230         {
 231             wxLogSysError(_("Couldn't change the state of event object."));
 232         }
 233     }
 234 }
 235
 236 // ----------------------------------------------------------------------------
 237 // wxCriticalSection implementation
 238 // ----------------------------------------------------------------------------
 239
 240 class wxCriticalSectionInternal
 241 {
 242 public:
 243     // init the critical section object
 244     wxCriticalSectionInternal()
 245         { ::InitializeCriticalSection(&m_data); }
 246
 247     // implicit cast to the associated data
 248     operator CRITICAL_SECTION *() { return &m_data; }
 249
 250     // free the associated ressources
 251     ~wxCriticalSectionInternal()
 252         { ::DeleteCriticalSection(&m_data); }
 253
 254 private:
 255     CRITICAL_SECTION m_data;
 256 };
 257
 258 wxCriticalSection::wxCriticalSection()
 259 {
 260     m_critsect = NULL;
 261 }
 262
 263 wxCriticalSection::~wxCriticalSection()
 264 {
 265     if ( m_critsect )
 266         delete m_critsect;
 267 }
 268
 269 void wxCriticalSection::Enter()
 270 {
 271     m_critsect = new wxCriticalSectionInternal;
 272
 273     ::EnterCriticalSection(*m_critsect);
 274 }
 275
 276 void wxCriticalSection::Leave()
 277 {
 278     wxCHECK_RET( m_critsect, "Leave() without matching Enter()" );
 279
 280     ::LeaveCriticalSection(*m_critsect);
 281 }
 282
 283 // ----------------------------------------------------------------------------
 284 // wxThread implementation
 285 // ----------------------------------------------------------------------------
 286
 287 // wxThreadInternal class
 288 // ----------------------
 289
 290 class wxThreadInternal
 291 {
 292 public:
 293     wxThreadInternal()
 294     {
 295         m_hThread = 0;
 296         m_state = STATE_NEW;
 297         m_priority = WXTHREAD_DEFAULT_PRIORITY;
 298     }
 299
 300     // create a new (suspended) thread (for the given thread object)
 301     bool Create(wxThread *thread);
 302
 303     // suspend/resume/terminate
 304     bool Suspend();
 305     bool Resume();
 306     void Cancel() { m_state = STATE_CANCELED; }
 307
 308     // thread state
 309     void SetState(wxThreadState state) { m_state = state; }
 310     wxThreadState GetState() const { return m_state; }
 311
 312     // thread priority
 313     void SetPriority(unsigned int priority) { m_priority = priority; }
 314     unsigned int GetPriority() const { return m_priority; }
 315
 316     // thread handle and id
 317     HANDLE GetHandle() const { return m_hThread; }
 318     DWORD  GetId() const { return m_tid; }
 319
 320     // thread function
 321     static DWORD WinThreadStart(wxThread *thread);
 322
 323 private:
 324     HANDLE        m_hThread;    // handle of the thread
 325     wxThreadState m_state;      // state, see wxThreadState enum
 326     unsigned int  m_priority;   // thread priority in "wx" units
 327     DWORD         m_tid;        // thread id
 328 };
 329
 330 DWORD wxThreadInternal::WinThreadStart(wxThread *thread)
 331 {
 332     // store the thread object in the TLS
 333     if ( !::TlsSetValue(s_tlsThisThread, thread) )
 334     {
 335         wxLogSysError(_("Can not start thread: error writing TLS."));
 336
 337         return (DWORD)-1;
 338     }
 339
 340     DWORD ret = (DWORD)thread->Entry();
 341     thread->p_internal->SetState(STATE_EXITED);
 342     thread->OnExit();
 343
 344     delete thread;
 345
 346     return ret;
 347 }
 348
 349 bool wxThreadInternal::Create(wxThread *thread)
 350 {
 351     m_hThread = ::CreateThread
 352                   (
 353                     NULL,                               // default security
 354                     0,                                  // default stack size
 355                     (LPTHREAD_START_ROUTINE)            // thread entry point
 356                     wxThreadInternal::WinThreadStart,   //
 357                     (LPVOID)thread,                     // parameter
 358                     CREATE_SUSPENDED,                   // flags
 359                     &m_tid                              // [out] thread id
 360                   );
 361
 362     if ( m_hThread == NULL )
 363     {
 364         wxLogSysError(_("Can't create thread"));
 365
 366         return FALSE;
 367     }
 368
 369     // translate wxWindows priority to the Windows one
 370     int win_priority;
 371     if (m_priority <= 20)
 372         win_priority = THREAD_PRIORITY_LOWEST;
 373     else if (m_priority <= 40)
 374         win_priority = THREAD_PRIORITY_BELOW_NORMAL;
 375     else if (m_priority <= 60)
 376         win_priority = THREAD_PRIORITY_NORMAL;
 377     else if (m_priority <= 80)
 378         win_priority = THREAD_PRIORITY_ABOVE_NORMAL;
 379     else if (m_priority <= 100)
 380         win_priority = THREAD_PRIORITY_HIGHEST;
 381     else
 382     {
 383         wxFAIL_MSG("invalid value of thread priority parameter");
 384         win_priority = THREAD_PRIORITY_NORMAL;
 385     }
 386
 387     if ( ::SetThreadPriority(m_hThread, win_priority) == 0 )
 388     {
 389         wxLogSysError(_("Can't set thread priority"));
 390     }
 391
 392     return TRUE;
 393 }
 394
 395 bool wxThreadInternal::Suspend()
 396 {
 397     DWORD nSuspendCount = ::SuspendThread(m_hThread);
 398     if ( nSuspendCount == (DWORD)-1 )
 399     {
 400         wxLogSysError(_("Can not suspend thread %x"), m_hThread);
 401
 402         return FALSE;
 403     }
 404
 405     m_state = STATE_PAUSED;
 406
 407     return TRUE;
 408 }
 409
 410 bool wxThreadInternal::Resume()
 411 {
 412     DWORD nSuspendCount = ::ResumeThread(m_hThread);
 413     if ( nSuspendCount == (DWORD)-1 )
 414     {
 415         wxLogSysError(_("Can not resume thread %x"), m_hThread);
 416
 417         return FALSE;
 418     }
 419
 420     m_state = STATE_RUNNING;
 421
 422     return TRUE;
 423 }
 424
 425 // static functions
 426 // ----------------
 427
 428 wxThread *wxThread::This()
 429 {
 430     wxThread *thread = (wxThread *)::TlsGetValue(s_tlsThisThread);
 431
 432     // be careful, 0 may be a valid return value as well
 433     if ( !thread && (::GetLastError() != NO_ERROR) )
 434     {
 435         wxLogSysError(_("Couldn't get the current thread pointer"));
 436
 437         // return NULL...
 438     }
 439
 440     return thread;
 441 }
 442
 443 bool wxThread::IsMain()
 444 {
 445     return ::GetCurrentThreadId() == s_idMainThread;
 446 }
 447
 448 void wxThread::Yield()
 449 {
 450     // 0 argument to Sleep() is special
 451     ::Sleep(0);
 452 }
 453
 454 void wxThread::Sleep(unsigned long milliseconds)
 455 {
 456     ::Sleep(milliseconds);
 457 }
 458
 459 // create/start thread
 460 // -------------------
 461
 462 wxThreadError wxThread::Create()
 463 {
 464     if ( !p_internal->Create(this) )
 465         return wxTHREAD_NO_RESOURCE;
 466
 467     return wxTHREAD_NO_ERROR;
 468 }
 469
 470 wxThreadError wxThread::Run()
 471 {
 472     wxCriticalSectionLocker lock(m_critsect);
 473
 474     if ( p_internal->GetState() != STATE_NEW )
 475     {
 476         // actually, it may be almost any state at all, not only STATE_RUNNING
 477         return wxTHREAD_RUNNING;
 478     }
 479
 480     return Resume();
 481 }
 482
 483 // suspend/resume thread
 484 // ---------------------
 485
 486 wxThreadError wxThread::Pause()
 487 {
 488     wxCriticalSectionLocker lock(m_critsect);
 489
 490     return p_internal->Suspend() ? wxTHREAD_NO_ERROR : wxTHREAD_MISC_ERROR;
 491 }
 492
 493 wxThreadError wxThread::Resume()
 494 {
 495     wxCriticalSectionLocker lock(m_critsect);
 496
 497     return p_internal->Resume() ? wxTHREAD_NO_ERROR : wxTHREAD_MISC_ERROR;
 498 }
 499
 500 // stopping thread
 501 // ---------------
 502
 503 wxThread::ExitCode wxThread::Delete()
 504 {
 505     ExitCode rc = 0;
 506
 507     // Delete() is always safe to call, so consider all possible states
 508     if ( IsPaused() )
 509         Resume();
 510
 511     if ( IsRunning() )
 512     {
 513         if ( IsMain() )
 514         {
 515             // set flag for wxIsWaitingForThread()
 516             s_waitingForThread = TRUE;
 517
 518             wxBeginBusyCursor();
 519         }
 520
 521         HANDLE hThread;
 522         {
 523             wxCriticalSectionLocker lock(m_critsect);
 524
 525             p_internal->Cancel();
 526             hThread = p_internal->GetHandle();
 527         }
 528
 529         // we can't just wait for the thread to terminate because it might be
 530         // calling some GUI functions and so it will never terminate before we
 531         // process the Windows messages that result from these functions
 532         DWORD result;
 533         do
 534         {
 535             result = ::MsgWaitForMultipleObjects
 536                      (
 537                        1,              // number of objects to wait for
 538                        &hThread,       // the objects
 539                        FALSE,          // don't wait for all objects
 540                        INFINITE,       // no timeout
 541                        QS_ALLEVENTS    // return as soon as there are any events
 542                      );
 543
 544             switch ( result )
 545             {
 546                 case 0xFFFFFFFF:
 547                     // error
 548                     wxLogSysError(_("Can not wait for thread termination"));
 549                     Kill();
 550                     return (ExitCode)-1;
 551
 552                 case WAIT_OBJECT_0:
 553                     // thread we're waiting for terminated
 554                     break;
 555
 556                 case WAIT_OBJECT_0 + 1:
 557                     // new message arrived, process it
 558                     if ( !wxTheApp->DoMessage() )
 559                     {
 560                         // WM_QUIT received: kill the thread
 561                         Kill();
 562
 563                         return (ExitCode)-1;
 564                     }
 565
 566                     if ( IsMain() )
 567                     {
 568                         // give the thread we're waiting for chance to exit
 569                         // from the GUI call it might have been in
 570                         if ( (s_nWaitingForGui > 0) && wxGuiOwnedByMainThread() )
 571                         {
 572                             wxMutexGuiLeave();
 573                         }
 574                     }
 575
 576                     break;
 577
 578                 default:
 579                     wxFAIL_MSG("unexpected result of MsgWaitForMultipleObject");
 580             }
 581         } while ( result != WAIT_OBJECT_0 );
 582
 583         if ( IsMain() )
 584         {
 585             s_waitingForThread = FALSE;
 586
 587             wxEndBusyCursor();
 588         }
 589
 590         if ( !::GetExitCodeThread(hThread, (LPDWORD)&rc) )
 591         {
 592             wxLogLastError("GetExitCodeThread");
 593
 594             rc = (ExitCode)-1;
 595         }
 596
 597         wxASSERT_MSG( (LPVOID)rc != (LPVOID)STILL_ACTIVE,
 598                       "thread must be already terminated." );
 599
 600         ::CloseHandle(hThread);
 601     }
 602
 603     return rc;
 604 }
 605
 606 wxThreadError wxThread::Kill()
 607 {
 608     if ( !IsRunning() )
 609         return wxTHREAD_NOT_RUNNING;
 610
 611     if ( !::TerminateThread(p_internal->GetHandle(), (DWORD)-1) )
 612     {
 613         wxLogSysError(_("Couldn't terminate thread"));
 614
 615         return wxTHREAD_MISC_ERROR;
 616     }
 617
 618     delete this;
 619
 620     return wxTHREAD_NO_ERROR;
 621 }
 622
 623 void wxThread::Exit(void *status)
 624 {
 625     delete this;
 626
 627     ::ExitThread((DWORD)status);
 628
 629     wxFAIL_MSG("Couldn't return from ExitThread()!");
 630 }
 631
 632 void wxThread::SetPriority(unsigned int prio)
 633 {
 634     wxCriticalSectionLocker lock(m_critsect);
 635
 636     p_internal->SetPriority(prio);
 637 }
 638
 639 unsigned int wxThread::GetPriority() const
 640 {
 641     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 642
 643     return p_internal->GetPriority();
 644 }
 645
 646 unsigned long wxThread::GetID() const
 647 {
 648     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 649
 650     return (unsigned long)p_internal->GetId();
 651 }
 652
 653 bool wxThread::IsRunning() const
 654 {
 655     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 656
 657     return p_internal->GetState() == STATE_RUNNING;
 658 }
 659
 660 bool wxThread::IsAlive() const
 661 {
 662     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 663
 664     return (p_internal->GetState() == STATE_RUNNING) ||
 665            (p_internal->GetState() == STATE_PAUSED);
 666 }
 667
 668 bool wxThread::TestDestroy()
 669 {
 670     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 671
 672     return p_internal->GetState() == STATE_CANCELED;
 673 }
 674
 675 wxThread::wxThread()
 676 {
 677     p_internal = new wxThreadInternal();
 678 }
 679
 680 wxThread::~wxThread()
 681 {
 682     delete p_internal;
 683 }
 684
 685 // ----------------------------------------------------------------------------
 686 // Automatic initialization for thread module
 687 // ----------------------------------------------------------------------------
 688
 689 class wxThreadModule : public wxModule
 690 {
 691 public:
 692     virtual bool OnInit();
 693     virtual void OnExit();
 694
 695 private:
 696     DECLARE_DYNAMIC_CLASS(wxThreadModule)
 697 };
 698
 699 IMPLEMENT_DYNAMIC_CLASS(wxThreadModule, wxModule)
 700
 701 bool wxThreadModule::OnInit()
 702 {
 703     // allocate TLS index for storing the pointer to the current thread
 704     s_tlsThisThread = ::TlsAlloc();
 705     if ( s_tlsThisThread == 0xFFFFFFFF )
 706     {
 707         // in normal circumstances it will only happen if all other
 708         // TLS_MINIMUM_AVAILABLE (>= 64) indices are already taken - in other
 709         // words, this should never happen
 710         wxLogSysError(_("Thread module initialization failed: "
 711                         "impossible to allocate index in thread "
 712                         "local storage"));
 713
 714         return FALSE;
 715     }
 716
 717     // main thread doesn't have associated wxThread object, so store 0 in the
 718     // TLS instead
 719     if ( !::TlsSetValue(s_tlsThisThread, (LPVOID)0) )
 720     {
 721         ::TlsFree(s_tlsThisThread);
 722         s_tlsThisThread = 0xFFFFFFFF;
 723
 724         wxLogSysError(_("Thread module initialization failed: "
 725                         "can not store value in thread local storage"));
 726
 727         return FALSE;
 728     }
 729
 730     s_critsectWaitingForGui = new wxCriticalSection();
 731
 732     s_critsectGui = new wxCriticalSection();
 733     s_critsectGui->Enter();
 734
 735     // no error return for GetCurrentThreadId()
 736     s_idMainThread = ::GetCurrentThreadId();
 737
 738     return TRUE;
 739 }
 740
 741 void wxThreadModule::OnExit()
 742 {
 743     if ( !::TlsFree(s_tlsThisThread) )
 744     {
 745         wxLogLastError("TlsFree failed.");
 746     }
 747
 748     if ( s_critsectGui )
 749     {
 750         s_critsectGui->Leave();
 751         delete s_critsectGui;
 752         s_critsectGui = NULL;
 753     }
 754
 755     wxDELETE(s_critsectWaitingForGui);
 756 }
 757
 758 // ----------------------------------------------------------------------------
 759 // under Windows, these functions are implemented usign a critical section and
 760 // not a mutex, so the names are a bit confusing
 761 // ----------------------------------------------------------------------------
 762
 763 void WXDLLEXPORT wxMutexGuiEnter()
 764 {
 765     // this would dead lock everything...
 766     wxASSERT_MSG( !wxThread::IsMain(),
 767                   "main thread doesn't want to block in wxMutexGuiEnter()!" );
 768
 769     // the order in which we enter the critical sections here is crucial!!
 770
 771     // set the flag telling to the main thread that we want to do some GUI
 772     {
 773         wxCriticalSectionLocker enter(*s_critsectWaitingForGui);
 774
 775         s_nWaitingForGui++;
 776     }
 777
 778     wxWakeUpMainThread();
 779
 780     // now we may block here because the main thread will soon let us in
 781     // (during the next iteration of OnIdle())
 782     s_critsectGui->Enter();
 783 }
 784
 785 void WXDLLEXPORT wxMutexGuiLeave()
 786 {
 787     wxCriticalSectionLocker enter(*s_critsectWaitingForGui);
 788
 789     if ( wxThread::IsMain() )
 790     {
 791         s_bGuiOwnedByMainThread = FALSE;
 792     }
 793     else
 794     {
 795         // decrement the number of waiters now
 796         wxASSERT_MSG( s_nWaitingForGui > 0,
 797                       "calling wxMutexGuiLeave() without entering it first?" );
 798
 799         s_nWaitingForGui--;
 800
 801         wxWakeUpMainThread();
 802     }
 803
 804     s_critsectGui->Leave();
 805 }
 806
 807 void WXDLLEXPORT wxMutexGuiLeaveOrEnter()
 808 {
 809     wxASSERT_MSG( wxThread::IsMain(),
 810                   "only main thread may call wxMutexGuiLeaveOrEnter()!" );
 811
 812     wxCriticalSectionLocker enter(*s_critsectWaitingForGui);
 813
 814     if ( s_nWaitingForGui == 0 )
 815     {
 816         // no threads are waiting for GUI - so we may acquire the lock without
 817         // any danger (but only if we don't already have it)
 818         if ( !wxGuiOwnedByMainThread() )
 819         {
 820             s_critsectGui->Enter();
 821
 822             s_bGuiOwnedByMainThread = TRUE;
 823         }
 824         //else: already have it, nothing to do
 825     }
 826     else
 827     {
 828         // some threads are waiting, release the GUI lock if we have it
 829         if ( wxGuiOwnedByMainThread() )
 830         {
 831             wxMutexGuiLeave();
 832         }
 833         //else: some other worker thread is doing GUI
 834     }
 835 }
 836
 837 bool WXDLLEXPORT wxGuiOwnedByMainThread()
 838 {
 839     return s_bGuiOwnedByMainThread;
 840 }
 841
 842 // wake up the main thread if it's in ::GetMessage()
 843 void WXDLLEXPORT wxWakeUpMainThread()
 844 {
 845     // sending any message would do - hopefully WM_NULL is harmless enough
 846     if ( !::PostThreadMessage(s_idMainThread, WM_NULL, 0, 0) )
 847     {
 848         // should never happen
 849         wxLogLastError("PostThreadMessage(WM_NULL)");
 850     }
 851 }
 852
 853 bool WXDLLEXPORT wxIsWaitingForThread()
 854 {
 855     return s_waitingForThread;
 856 }
 857
 858 #endif // wxUSE_THREADS