text: /////////////////////////////////////////////////////////////////////////////
  // Name:        wx/thread.h
  // Purpose:     Thread API
  // Author:      Guilhem Lavaux
  // Modified by: Vadim Zeitlin (modifications partly inspired by omnithreads
  //              package from Olivetti & Oracle Research Laboratory)
  // Created:     04/13/98
  // Copyright:   (c) Guilhem Lavaux
  // Licence:     wxWindows licence
  /////////////////////////////////////////////////////////////////////////////
  #ifndef _WX_THREAD_H_
  #  define _WX_THREAD_H_
  // ----------------------------------------------------------------------------
  // headers
  // ----------------------------------------------------------------------------
  
  // get the value of wxUSE_THREADS configuration flag
  #  include "wx/defs.h"
  #  if  wxUSE_THREADS
  // ----------------------------------------------------------------------------
  // constants
  // ----------------------------------------------------------------------------
  enum wxMutexError {
      wxMUTEX_NO_ERROR = 0,   // operation completed successfully
      wxMUTEX_INVALID,        // mutex hasn't been initialized
      wxMUTEX_DEAD_LOCK,      // mutex is already locked by the calling thread
      wxMUTEX_BUSY,           // mutex is already locked by another thread
      wxMUTEX_UNLOCKED,       // attempt to unlock a mutex which is not locked
      wxMUTEX_TIMEOUT,        // LockTimeout() has timed out
      wxMUTEX_MISC_ERROR      // any other error
  };
  enum wxCondError {
      wxCOND_NO_ERROR = 0,
      wxCOND_INVALID,
      wxCOND_TIMEOUT,         // WaitTimeout() has timed out
      wxCOND_MISC_ERROR
  };
  enum wxSemaError {
      wxSEMA_NO_ERROR = 0,
      wxSEMA_INVALID,         // semaphore hasn't been initialized successfully
      wxSEMA_BUSY,            // returned by TryWait() if Wait() would block
      wxSEMA_TIMEOUT,         // returned by WaitTimeout()
      wxSEMA_OVERFLOW,        // Post() would increase counter past the max
      wxSEMA_MISC_ERROR
  };
  enum wxThreadError {
      wxTHREAD_NO_ERROR = 0,      // No error
      wxTHREAD_NO_RESOURCE,       // No resource left to create a new thread
      wxTHREAD_RUNNING,           // The thread is already running
      wxTHREAD_NOT_RUNNING,       // The thread isn't running
      wxTHREAD_KILLED,            // Thread we waited for had to be killed
      wxTHREAD_MISC_ERROR         // Some other error
  };
  enum wxThreadKind {
      wxTHREAD_DETACHED,
      wxTHREAD_JOINABLE
  };
  enum wxThreadWait {
      wxTHREAD_WAIT_BLOCK,
      wxTHREAD_WAIT_YIELD,       // process events while waiting; MSW only
  
      // For compatibility reasons we use wxTHREAD_WAIT_YIELD by default as this
      // was the default behaviour of wxMSW 2.8 but it should be avoided as it's
      // dangerous and not portable.
  #if WXWIN_COMPATIBILITY_2_8
      wxTHREAD_WAIT_DEFAULT = wxTHREAD_WAIT_YIELD
  #else
      wxTHREAD_WAIT_DEFAULT = wxTHREAD_WAIT_BLOCK
  #endif
  };
  // Obsolete synonyms for wxPRIORITY_XXX for backwards compatibility-only
  enum
  {
    WXTHREAD_MIN_PRIORITY = wxPRIORITY_MIN,
    WXTHREAD_DEFAULT_PRIORITY = wxPRIORITY_DEFAULT,
    WXTHREAD_MAX_PRIORITY = wxPRIORITY_MAX
  };
  // There are 2 types of mutexes: normal mutexes and recursive ones. The attempt
  // to lock a normal mutex by a thread which already owns it results in
  // undefined behaviour (it always works under Windows, it will almost always
  // result in a deadlock under Unix). Locking a recursive mutex in such
  // situation always succeeds and it must be unlocked as many times as it has
  // been locked.
  //
  // However recursive mutexes have several important drawbacks: first, in the
  // POSIX implementation, they're less efficient. Second, and more importantly,
  // they CAN NOT BE USED WITH CONDITION VARIABLES under Unix! Using them with
  // wxCondition will work under Windows and some Unices (notably Linux) but will
  // deadlock under other Unix versions (e.g. Solaris). As it might be difficult
  // to ensure that a recursive mutex is not used with wxCondition, it is a good
  // idea to avoid using recursive mutexes at all. Also, the last problem with
  // them is that some (older) Unix versions don't support this at all -- which
  // results in a configure warning when building and a deadlock when using them.
  enum wxMutexType {
      // normal mutex: try to always use this one
      wxMUTEX_DEFAULT,
  
      // recursive mutex: don't use these ones with wxCondition
      wxMUTEX_RECURSIVE
  };
  // forward declarations
  class WXDLLIMPEXP_FWD_BASE wxThreadHelper;
  class WXDLLIMPEXP_FWD_BASE wxConditionInternal;
  class WXDLLIMPEXP_FWD_BASE wxMutexInternal;
  class WXDLLIMPEXP_FWD_BASE wxSemaphoreInternal;
  class WXDLLIMPEXP_FWD_BASE wxThreadInternal;
  // ----------------------------------------------------------------------------
  // A mutex object is a synchronization object whose state is set to signaled
  // when it is not owned by any thread, and nonsignaled when it is owned. Its
  // name comes from its usefulness in coordinating mutually-exclusive access to
  // a shared resource. Only one thread at a time can own a mutex object.
  // ----------------------------------------------------------------------------
  
  // you should consider wxMutexLocker whenever possible instead of directly
  // working with wxMutex class - it is safer
  class WXDLLIMPEXP_BASE wxMutex
  {
  public:
      // constructor & destructor
      // ------------------------
  
      // create either default (always safe) or recursive mutex
    wxMutex(wxMutexType mutexType = wxMUTEX_DEFAULT);
      // destroys the mutex kernel object
    ~wxMutex();
      // test if the mutex has been created successfully
    bool IsOk() const;
      // mutex operations
      // ----------------
  
      // Lock the mutex, blocking on it until it is unlocked by the other thread.
      // The result of locking a mutex already locked by the current thread
      // depend on the mutex type.
      //
      // The caller must call Unlock() later if Lock() returned wxMUTEX_NO_ERROR.
    wxMutexError Lock();
      // Same as Lock() but return wxMUTEX_TIMEOUT if the mutex can't be locked
      // during the given number of milliseconds
    wxMutexError LockTimeout(unsigned long ms);
      // Try to lock the mutex: if it is currently locked, return immediately
      // with an error. Otherwise the caller must call Unlock().
    wxMutexError TryLock();
      // Unlock the mutex. It is an error to unlock an already unlocked mutex
    wxMutexError Unlock();
  protected:
    wxMutexInternal* m_internal;
    friend class wxConditionInternal;
    wxDECLARE_NO_COPY_CLASS(wxMutex);
  };
  // a helper class which locks the mutex in the ctor and unlocks it in the dtor:
  // this ensures that mutex is always unlocked, even if the function returns or
  // throws an exception before it reaches the end
  class WXDLLIMPEXP_BASE wxMutexLocker
  {
  public:
      // lock the mutex in the ctor
    wxMutexLocker(wxMutex& mutex)
      : m_isOk(false)
      , m_mutex(mutex)
    {
      m_isOk = (m_mutex.Lock() == wxMUTEX_NO_ERROR);
    }
      // returns true if mutex was successfully locked in ctor
    bool IsOk() const
    {
      return m_isOk;
    }
      // unlock the mutex in dtor
    ~wxMutexLocker()
    {
      if (IsOk())
      {
        m_mutex.Unlock();
      }
    }
  private:
      // no assignment operator nor copy ctor
    wxMutexLocker(const wxMutexLocker&);
    wxMutexLocker& operator=(const wxMutexLocker&);
    bool m_isOk;
    wxMutex& m_mutex;
  };
  // ----------------------------------------------------------------------------
  // Critical section: this is the same as mutex but is only visible to the
  // threads of the same process. For the platforms which don't have native
  // support for critical sections, they're implemented entirely in terms of
  // mutexes.
  //
  // NB: wxCriticalSection object does not allocate any memory in its ctor
  //     which makes it possible to have static globals of this class
  // ----------------------------------------------------------------------------
  
  // in order to avoid any overhead under platforms where critical sections are
  // just mutexes make all wxCriticalSection class functions inline
  #    if  !defined(__WINDOWS__)
  #      define wxCRITSECT_IS_MUTEX	1
  #      define wxCRITSECT_INLINE	WXEXPORT inline
  #    else 
  #      define wxCRITSECT_IS_MUTEX	0
  #      define wxCRITSECT_INLINE
  #    endif
  enum wxCriticalSectionType {
      // recursive critical section
      wxCRITSEC_DEFAULT,
  
      // non-recursive critical section
      wxCRITSEC_NON_RECURSIVE
  };
  // you should consider wxCriticalSectionLocker whenever possible instead of
  // directly working with wxCriticalSection class - it is safer
  class WXDLLIMPEXP_BASE wxCriticalSection
  {
  public:
      // ctor & dtor
    wxCRITSECT_INLINE wxCriticalSection(wxCriticalSectionType critSecType = wxCRITSEC_DEFAULT);
    wxCRITSECT_INLINE ~wxCriticalSection();
      // enter the section (the same as locking a mutex)
    wxCRITSECT_INLINE void Enter();
      // try to enter the section (the same as trying to lock a mutex)
    wxCRITSECT_INLINE bool TryEnter();
      // leave the critical section (same as unlocking a mutex)
    wxCRITSECT_INLINE void Leave();
  #    if  wxCRITSECT_IS_MUTEX
  private:
    wxMutex m_mutex;
  #    elif  defined(__WINDOWS__)
      // we can't allocate any memory in the ctor, so use placement new -
      // unfortunately, we have to hardcode the sizeof() here because we can't
      // include windows.h from this public header and we also have to use the
      // union to force the correct (i.e. maximal) alignment
      //
      // if CRITICAL_SECTION size changes in Windows, you'll get an assert from
      // thread.cpp and will need to increase the buffer size
  #      ifdef __WIN64__
    typedef char wxCritSectBuffer[40];
  #      else 
    typedef char wxCritSectBuffer[24];
  #      endif
    union 
    {
      unsigned long m_dummy1;
      void* m_dummy2;
      wxCritSectBuffer m_buffer;
    };
  #    endif
    wxDECLARE_NO_COPY_CLASS(wxCriticalSection);
  };
  #    if  wxCRITSECT_IS_MUTEX
      // implement wxCriticalSection using mutexes
  inline wxCriticalSection::wxCriticalSection(wxCriticalSectionType critSecType)
    : m_mutex(critSecType == wxCRITSEC_DEFAULT ? wxMUTEX_RECURSIVE : wxMUTEX_DEFAULT)
  {
  }
  inline wxCriticalSection::~wxCriticalSection()
  {
  }
  inline void wxCriticalSection::Enter()
  {
    (void) m_mutex.Lock();
  }
  inline bool wxCriticalSection::TryEnter()
  {
    return m_mutex.TryLock() == wxMUTEX_NO_ERROR;
  }
  inline void wxCriticalSection::Leave()
  {
    (void) m_mutex.Unlock();
  }
  #    endif
  #    undef wxCRITSECT_INLINE
  #    undef wxCRITSECT_IS_MUTEX
  // wxCriticalSectionLocker is the same to critical sections as wxMutexLocker is
  // to mutexes
  class WXDLLIMPEXP_BASE wxCriticalSectionLocker
  {
  public:
    wxCriticalSectionLocker(wxCriticalSection& cs)
      : m_critsect(cs)
    {
      m_critsect.Enter();
    }
    ~wxCriticalSectionLocker()
    {
      m_critsect.Leave();
    }
  private:
    wxCriticalSection& m_critsect;
    wxDECLARE_NO_COPY_CLASS(wxCriticalSectionLocker);
  };
  // ----------------------------------------------------------------------------
  // wxCondition models a POSIX condition variable which allows one (or more)
  // thread(s) to wait until some condition is fulfilled
  // ----------------------------------------------------------------------------
  class WXDLLIMPEXP_BASE wxCondition
  {
  public:
      // Each wxCondition object is associated with a (single) wxMutex object.
      // The mutex object MUST be locked before calling Wait()
    wxCondition(wxMutex& mutex);
      // dtor is not virtual, don't use this class polymorphically
    ~wxCondition();
      // return true if the condition has been created successfully
    bool IsOk() const;
      // NB: the associated mutex MUST be locked beforehand by the calling thread
      //
      // it atomically releases the lock on the associated mutex
      // and starts waiting to be woken up by a Signal()/Broadcast()
      // once its signaled, then it will wait until it can reacquire
      // the lock on the associated mutex object, before returning.
    wxCondError Wait();
      // std::condition_variable-like variant that evaluates the associated condition
    template <typename Functor>
    wxCondError Wait(const Functor& predicate)
    {
      while (!predicate())
      {
        wxCondError e = Wait();
        if (e != wxCOND_NO_ERROR)
        {
          return e;
        }
      }
      return wxCOND_NO_ERROR;
    }
      // exactly as Wait() except that it may also return if the specified
      // timeout elapses even if the condition hasn't been signalled: in this
      // case, the return value is wxCOND_TIMEOUT, otherwise (i.e. in case of a
      // normal return) it is wxCOND_NO_ERROR.
      //
      // the timeout parameter specifies an interval that needs to be waited for
      // in milliseconds
    wxCondError WaitTimeout(unsigned long milliseconds);
      // NB: the associated mutex may or may not be locked by the calling thread
      //
      // this method unblocks one thread if any are blocking on the condition.
      // if no thread is blocking in Wait(), then the signal is NOT remembered
      // The thread which was blocking on Wait() will then reacquire the lock
      // on the associated mutex object before returning
    wxCondError Signal();
      // NB: the associated mutex may or may not be locked by the calling thread
      //
      // this method unblocks all threads if any are blocking on the condition.
      // if no thread is blocking in Wait(), then the signal is NOT remembered
      // The threads which were blocking on Wait() will then reacquire the lock
      // on the associated mutex object before returning.
    wxCondError Broadcast();
  private:
    wxConditionInternal* m_internal;
    wxDECLARE_NO_COPY_CLASS(wxCondition);
  };
  // ----------------------------------------------------------------------------
  // wxSemaphore: a counter limiting the number of threads concurrently accessing
  //              a shared resource
  // ----------------------------------------------------------------------------
  class WXDLLIMPEXP_BASE wxSemaphore
  {
  public:
      // specifying a maxcount of 0 actually makes wxSemaphore behave as if there
      // is no upper limit, if maxcount is 1 the semaphore behaves as a mutex
    wxSemaphore(int initialcount = 0, int maxcount = 0);
      // dtor is not virtual, don't use this class polymorphically
    ~wxSemaphore();
      // return true if the semaphore has been created successfully
    bool IsOk() const;
      // wait indefinitely, until the semaphore count goes beyond 0
      // and then decrement it and return (this method might have been called
      // Acquire())
    wxSemaError Wait();
      // same as Wait(), but does not block, returns wxSEMA_NO_ERROR if
      // successful and wxSEMA_BUSY if the count is currently zero
    wxSemaError TryWait();
      // same as Wait(), but as a timeout limit, returns wxSEMA_NO_ERROR if the
      // semaphore was acquired and wxSEMA_TIMEOUT if the timeout has elapsed
    wxSemaError WaitTimeout(unsigned long milliseconds);
      // increments the semaphore count and signals one of the waiting threads
    wxSemaError Post();
  private:
    wxSemaphoreInternal* m_internal;
    wxDECLARE_NO_COPY_CLASS(wxSemaphore);
  };
  // ----------------------------------------------------------------------------
  // wxThread: class encapsulating a thread of execution
  // ----------------------------------------------------------------------------
  
  // there are two different kinds of threads: joinable and detached (default)
  // ones. Only joinable threads can return a return code and only detached
  // threads auto-delete themselves - the user should delete the joinable
  // threads manually.
  
  // NB: in the function descriptions the words "this thread" mean the thread
  //     created by the wxThread object while "main thread" is the thread created
  //     during the process initialization (a.k.a. the GUI thread)
  
  // On VMS thread pointers are 64 bits (also needed for other systems???
  #    ifdef __VMS
  typedef unsigned long long wxThreadIdType;
  #    else 
  typedef unsigned long wxThreadIdType;
  #    endif
  class WXDLLIMPEXP_BASE wxThread
  {
  public:
      // the return type for the thread function
    typedef void* ExitCode;
      // static functions
          // Returns the wxThread object for the calling thread. NULL is returned
          // if the caller is the main thread (but it's recommended to use
          // IsMain() and only call This() for threads other than the main one
          // because NULL is also returned on error). If the thread wasn't
          // created with wxThread class, the returned value is undefined.
    static wxThread* This();
          // Returns true if current thread is the main thread.
          //
          // Notice that it also returns true if main thread id hadn't been
          // initialized yet on the assumption that it's too early in wx startup
          // process for any other threads to have been created in this case.
    static bool IsMain()
    {
      return !ms_idMainThread || GetCurrentId() == ms_idMainThread;
    }
          // Return the main thread id
    static wxThreadIdType GetMainId()
    {
      return ms_idMainThread;
    }
          // Release the rest of our time slice letting the other threads run
    static void Yield();
          // Sleep during the specified period of time in milliseconds
          //
          // This is the same as wxMilliSleep().
    static void Sleep(unsigned long milliseconds);
          // get the number of system CPUs - useful with SetConcurrency()
          // (the "best" value for it is usually number of CPUs + 1)
          //
          // Returns -1 if unknown, number of CPUs otherwise
    static int GetCPUCount();
          // Get the platform specific thread ID and return as a long.  This
          // can be used to uniquely identify threads, even if they are not
          // wxThreads.  This is used by wxPython.
    static wxThreadIdType GetCurrentId();
          // sets the concurrency level: this is, roughly, the number of threads
          // the system tries to schedule to run in parallel. 0 means the
          // default value (usually acceptable, but may not yield the best
          // performance for this process)
          //
          // Returns true on success, false otherwise (if not implemented, for
          // example)
    static bool SetConcurrency(size_t level);
      // constructor only creates the C++ thread object and doesn't create (or
      // start) the real thread
    wxThread(wxThreadKind kind = wxTHREAD_DETACHED);
      // functions that change the thread state: all these can only be called
      // from _another_ thread (typically the thread that created this one, e.g.
      // the main thread), not from the thread itself
  
          // create a new thread and optionally set the stack size on
          // platforms that support that - call Run() to start it
    wxThreadError Create(unsigned int stackSize = 0);
          // starts execution of the thread - from the moment Run() is called
          // the execution of wxThread::Entry() may start at any moment, caller
          // shouldn't suppose that it starts after (or before) Run() returns.
    wxThreadError Run();
          // stops the thread if it's running and deletes the wxThread object if
          // this is a detached thread freeing its memory - otherwise (for
          // joinable threads) you still need to delete wxThread object
          // yourself.
          //
          // this function only works if the thread calls TestDestroy()
          // periodically - the thread will only be deleted the next time it
          // does it!
          //
          // will fill the rc pointer with the thread exit code if it's !NULL
    wxThreadError Delete(ExitCode* rc = NULL, wxThreadWait waitMode = wxTHREAD_WAIT_DEFAULT);
          // waits for a joinable thread to finish and returns its exit code
          //
          // Returns (ExitCode)-1 on error (for example, if the thread is not
          // joinable)
    ExitCode Wait(wxThreadWait waitMode = wxTHREAD_WAIT_DEFAULT);
          // kills the thread without giving it any chance to clean up - should
          // not be used under normal circumstances, use Delete() instead.
          // It is a dangerous function that should only be used in the most
          // extreme cases!
          //
          // The wxThread object is deleted by Kill() if the thread is
          // detachable, but you still have to delete it manually for joinable
          // threads.
    wxThreadError Kill();
          // pause a running thread: as Delete(), this only works if the thread
          // calls TestDestroy() regularly
    wxThreadError Pause();
          // resume a paused thread
    wxThreadError Resume();
      // priority
          // Sets the priority to "prio" which must be in 0..100 range (see
          // also wxPRIORITY_XXX constants).
    void SetPriority(unsigned int prio);
          // Get the current priority.
    unsigned int GetPriority() const;
      // thread status inquiries
          // Returns true if the thread is alive: i.e. running or suspended
    bool IsAlive() const;
          // Returns true if the thread is running (not paused, not killed).
    bool IsRunning() const;
          // Returns true if the thread is suspended
    bool IsPaused() const;
          // is the thread of detached kind?
    bool IsDetached() const
    {
      return m_isDetached;
    }
      // Get the thread ID - a platform dependent number which uniquely
      // identifies a thread inside a process
    wxThreadIdType GetId() const;
  #    ifdef __WINDOWS__
      // Get the internal OS handle
    WXHANDLE MSWGetHandle() const;
  #    endif
    wxThreadKind GetKind() const
    {
      return m_isDetached ? wxTHREAD_DETACHED : wxTHREAD_JOINABLE;
    }
      // Returns true if the thread was asked to terminate: this function should
      // be called by the thread from time to time, otherwise the main thread
      // will be left forever in Delete()!
    virtual bool TestDestroy();
      // dtor is public, but the detached threads should never be deleted - use
      // Delete() instead (or leave the thread terminate by itself)
    virtual ~wxThread();
  protected:
      // exits from the current thread - can be called only from this thread
    void Exit(ExitCode exitcode = NULL);
      // entry point for the thread - called by Run() and executes in the context
      // of this thread.
    virtual void* Entry() = 0;
      // use this to call the Entry() virtual method
    void* CallEntry();
      // Callbacks which may be overridden by the derived class to perform some
      // specific actions when the thread is deleted or killed. By default they
      // do nothing.
  
      // This one is called by Delete() before actually deleting the thread and
      // is executed in the context of the thread that called Delete().
    virtual void OnDelete()
    {
    }
      // This one is called by Kill() before killing the thread and is executed
      // in the context of the thread that called Kill().
    virtual void OnKill()
    {
    }
      // called when the thread exits - in the context of this thread
      //
      // NB: this function will not be called if the thread is Kill()ed
    virtual void OnExit()
    {
    }
  private:
      // no copy ctor/assignment operator
    wxThread(const wxThread&);
    wxThread& operator=(const wxThread&);
    friend class wxThreadInternal;
    friend class wxThreadModule;
      // the main thread identifier, should be set on startup
    static wxThreadIdType ms_idMainThread;
      // the (platform-dependent) thread class implementation
    wxThreadInternal* m_internal;
      // protects access to any methods of wxThreadInternal object
    mutable wxCriticalSection m_critsect;
      // true if the thread is detached, false if it is joinable
    bool m_isDetached;
  };
  // wxThreadHelperThread class
  // --------------------------
  class WXDLLIMPEXP_BASE wxThreadHelperThread : public wxThread
  {
  public:
      // constructor only creates the C++ thread object and doesn't create (or
      // start) the real thread
    wxThreadHelperThread(wxThreadHelper& owner, wxThreadKind kind)
      : wxThread(kind)
      , m_owner(owner)
    {
    }
  protected:
      // entry point for the thread -- calls Entry() in owner.
    void* Entry() override;
  private:
      // the owner of the thread
    wxThreadHelper& m_owner;
      // no copy ctor/assignment operator
    wxThreadHelperThread(const wxThreadHelperThread&);
    wxThreadHelperThread& operator=(const wxThreadHelperThread&);
  };
  // ----------------------------------------------------------------------------
  // wxThreadHelper: this class implements the threading logic to run a
  // background task in another object (such as a window).  It is a mix-in: just
  // derive from it to implement a threading background task in your class.
  // ----------------------------------------------------------------------------
  class WXDLLIMPEXP_BASE wxThreadHelper
  {
  private:
    void KillThread()
    {
          // If wxThreadHelperThread is detached and is about to finish, it will
          // set m_thread to NULL so don't delete it then.
          // But if KillThread is called before wxThreadHelperThread (in detached mode)
          // sets it to NULL, then the thread object still exists and can be killed
      wxCriticalSectionLocker locker(m_critSection);
      if (m_thread)
      {
        m_thread->Kill();
        if (m_kind == wxTHREAD_JOINABLE)
        {
          delete m_thread;
        }
        m_thread = NULL;
      }
    }
  public:
      // constructor only initializes m_thread to NULL
    wxThreadHelper(wxThreadKind kind = wxTHREAD_JOINABLE)
      : m_thread(NULL)
      , m_kind(kind)
    {
    }
      // destructor deletes m_thread
    virtual ~wxThreadHelper()
    {
      KillThread();
    }
      // create a new thread (and optionally set the stack size on platforms that
      // support/need that), call Run() to start it
    wxThreadError CreateThread(wxThreadKind kind = wxTHREAD_JOINABLE, unsigned int stackSize = 0)
    {
      KillThread();
      m_kind = kind;
      m_thread = new wxThreadHelperThread(*this, m_kind);
      return m_thread->Create(stackSize);
    }
      // entry point for the thread - called by Run() and executes in the context
      // of this thread.
    virtual void* Entry() = 0;
      // returns a pointer to the thread which can be used to call Run()
    wxThread* GetThread() const
    {
      wxCriticalSectionLocker locker(m_critSection);
      wxThread* thread = m_thread;
      return thread;
    }
  protected:
    wxThread* m_thread;
    wxThreadKind m_kind;
    mutable wxCriticalSection m_critSection;
    friend class wxThreadHelperThread;
  };
  // call Entry() in owner, put it down here to avoid circular declarations
  inline void* wxThreadHelperThread::Entry()
  {
    void* const result = m_owner.Entry();
    wxCriticalSectionLocker locker(m_owner.m_critSection);
      // Detached thread will be deleted after returning, so make sure
      // wxThreadHelper::GetThread will not return an invalid pointer.
      // And that wxThreadHelper::KillThread will not try to kill
      // an already deleted thread
    if (m_owner.m_kind == wxTHREAD_DETACHED)
    {
      m_owner.m_thread = NULL;
    }
    return result;
  }
  // ----------------------------------------------------------------------------
  // Automatic initialization
  // ----------------------------------------------------------------------------
  
  // GUI mutex handling.
  void WXDLLIMPEXP_BASE wxMutexGuiEnter();
  void WXDLLIMPEXP_BASE wxMutexGuiLeave();
  // macros for entering/leaving critical sections which may be used without
  // having to take them inside "#if wxUSE_THREADS"
  #    define wxENTER_CRIT_SECT(cs)   (cs).Enter()
  #    define wxLEAVE_CRIT_SECT(cs)   (cs).Leave()
  #    define wxCRIT_SECT_DECLARE(cs)	 static wxCriticalSection cs
  #    define wxCRIT_SECT_DECLARE_MEMBER(cs)	 wxCriticalSection cs
  #    define wxCRIT_SECT_LOCKER(name, cs)	  wxCriticalSectionLocker name(cs)
  // function for checking if we're in the main thread which may be used whether
  // wxUSE_THREADS is 0 or 1
  inline bool wxIsMainThread()
  {
    return wxThread::IsMain();
  }
  #  else 
  // no thread support
  inline void wxMutexGuiEnter()
  {
  }
  inline void wxMutexGuiLeave()
  {
  }
  // macros for entering/leaving critical sections which may be used without
  // having to take them inside "#if wxUSE_THREADS"
  // (the implementation uses dummy structs to force semicolon after the macro)
  #    define wxENTER_CRIT_SECT(cs)	            do {} while (0)
  #    define wxLEAVE_CRIT_SECT(cs)	            do {} while (0)
  #    define wxCRIT_SECT_DECLARE(cs)	          struct wxDummyCS##cs
  #    define wxCRIT_SECT_DECLARE_MEMBER(cs)	   struct wxDummyCSMember##cs { }
  #    define wxCRIT_SECT_LOCKER(name, cs)	     struct wxDummyCSLocker##name
  // if there is only one thread, it is always the main one
  inline bool wxIsMainThread()
  {
    return true;
  }
  #  endif
  // mark part of code as being a critical section: this macro declares a
  // critical section with the given name and enters it immediately and leaves
  // it at the end of the current scope
  //
  // example:
  //
  //      int Count()
  //      {
  //          static int s_counter = 0;
  //
  //          wxCRITICAL_SECTION(counter);
  //
  //          return ++s_counter;
  //      }
  //
  // this function is MT-safe in presence of the threads but there is no
  // overhead when the library is compiled without threads
  #  define wxCRITICAL_SECTION(name)	 \
      wxCRIT_SECT_DECLARE(s_cs##name);  \
      wxCRIT_SECT_LOCKER(cs##name##Locker, s_cs##name)
  // automatically lock GUI mutex in ctor and unlock it in dtor
  class WXDLLIMPEXP_BASE wxMutexGuiLocker
  {
  public:
    wxMutexGuiLocker()
    {
      wxMutexGuiEnter();
    }
    ~wxMutexGuiLocker()
    {
      wxMutexGuiLeave();
    }
  };
  // -----------------------------------------------------------------------------
  // implementation only until the end of file
  // -----------------------------------------------------------------------------
  #  if  wxUSE_THREADS
  #    if  defined(__WINDOWS__) || defined(__DARWIN__)
      // unlock GUI if there are threads waiting for and lock it back when
      // there are no more of them - should be called periodically by the main
      // thread
  extern void WXDLLIMPEXP_BASE wxMutexGuiLeaveOrEnter();
      // returns true if the main thread has GUI lock
  extern bool WXDLLIMPEXP_BASE wxGuiOwnedByMainThread();
      // wakes up the main thread if it's sleeping inside ::GetMessage()
  extern void WXDLLIMPEXP_BASE wxWakeUpMainThread();
  #      ifndef __DARWIN__
      // return true if the main thread is waiting for some other to terminate:
      // wxApp then should block all "dangerous" messages
  extern bool WXDLLIMPEXP_BASE wxIsWaitingForThread();
  #      endif
  #    endif
  #  endif
  #endif
  