added wxLocale::IsAvailable() (extended patch 1547191)

[wxWidgets.git] / docs / latex / wx / thread.tex

diff --git a/docs/latex/wx/thread.tex b/docs/latex/wx/thread.tex
index 8910946811d71e88a6c629577421647ac9c9d38b..12f9020b7401d7de4b3717eab94541d6f3aba729 100644 (file)
--- a/docs/latex/wx/thread.tex
+++ b/docs/latex/wx/thread.tex
@@ -1,12 +1,15 @@
 \section{\class{wxThread}}\label{wxthread}
 
 \section{\class{wxThread}}\label{wxthread}
 

-A thread is basically a path of execution through a program. Threads are also
+A thread is basically a path of execution through a program. Threads are

 sometimes called {\it light-weight processes}, but the fundamental difference
 between threads and processes is that memory spaces of different processes are
 sometimes called {\it light-weight processes}, but the fundamental difference
 between threads and processes is that memory spaces of different processes are

-separated while all threads share the same address space. While it makes it
-much easier to share common data between several threads, it also makes much
-easier to shoot oneself in the foot, so careful use of synchronization objects
-such as \helpref{mutexes}{wxmutex} and/or \helpref{critical sections}{wxcriticalsection} is recommended.
+separated while all threads share the same address space. 
+
+While it makes it much easier to share common data between several threads, it also 
+makes it much easier to shoot oneself in the foot, so careful use of synchronization 
+objects such as \helpref{mutexes}{wxmutex} or \helpref{critical sections}{wxcriticalsection} is recommended. In addition, don't create global thread 
+objects because they allocate memory in their constructor, which will cause 
+problems for the memory checking system.

 
 \wxheading{Derived from}
 
 
 \wxheading{Derived from}
 


@@ -22,28 +25,157 @@ None.
 
 \latexignore{\rtfignore{\wxheading{Members}}}
 
 
 \latexignore{\rtfignore{\wxheading{Members}}}
 

+\membersection{Types of wxThreads}\label{typeswxthread}
+
+There are two types of threads in wxWidgets: {\it detached} and {\it joinable},
+modeled after the the POSIX thread API. This is different from the Win32 API
+where all threads are joinable. 
+
+By default wxThreads in wxWidgets use the detached behavior. Detached threads
+delete themselves once they have completed, either by themselves when they complete 
+processing or through a call to \helpref{wxThread::Delete}{wxthreaddelete}, and thus 
+must be created on the heap (through the new operator, for example). Conversely, 
+joinable threads do not delete themselves when they are done processing and as such
+are safe to create on the stack. Joinable threads also provide the ability
+for one to get value it returned from \helpref{wxThread::Entry}{wxthreadentry}
+through \helpref{wxThread::Wait}{wxthreadwait}.
+
+You shouldn't hurry to create all the threads joinable, however, because this
+has a disadvantage as well: you {\bf must} Wait() for a joinable thread or the
+system resources used by it will never be freed, and you also must delete the
+corresponding wxThread object yourself if you did not create it on the stack. In 
+contrast, detached threads are of the "fire-and-forget" kind: you only have to start 
+a detached thread and it will terminate and destroy itself.
+
+\membersection{wxThread deletion}\label{deletionwxthread}
+
+Regardless of whether it has terminated or not, you should call 
+\helpref{wxThread::Wait}{wxthreadwait} on a joinable thread to release its
+memory, as outlined in \helpref{Types of wxThreads}{typeswxthread}. If you created
+a joinable thread on the heap, remember to delete it manually with the delete 
+operator or similar means as only detached threads handle this type of memory 
+management.
+
+Since detached threads delete themselves when they are finished processing,
+you should take care when calling a routine on one. If you are certain the 
+thread is still running and would like to end it, you may call 
+\helpref{wxThread::Delete}{wxthreaddelete} to gracefully end it (which implies
+that the thread will be deleted after that call to Delete()). It should be
+implied that you should never attempt to delete a detached thread with the 
+delete operator or similar means. 
+
+As mentioned, \helpref{wxThread::Wait}{wxthreadwait} or 
+\helpref{wxThread::Delete}{wxthreaddelete} attempts to gracefully terminate
+a joinable and detached thread, respectively. It does this by waiting until
+the thread in question calls \helpref{wxThread::TestDestroy}{wxthreadtestdestroy}
+or ends processing (returns from \helpref{wxThread::Entry}{wxthreadentry}).
+
+Obviously, if the thread does call TestDestroy() and does not end the calling
+thread will come to halt. This is why it is important to call TestDestroy() in
+the Entry() routine of your threads as often as possible.
+
+As a last resort you can end the thread immediately through 
+\helpref{wxThread::Kill}{wxthreadkill}. It is strongly recommended that you
+do not do this, however, as it does not free the resources associated with
+the object (although the wxThread object of detached threads will still be
+deleted) and could leave the C runtime library in an undefined state.
+
+\membersection{wxWidgets calls in secondary threads}\label{secondarywxthread}
+
+All threads other then the "main application thread" (the one
+\helpref{wxApp::OnInit}{wxapponinit} or your main function runs in, for 
+example) are considered "secondary threads". These include all threads created 
+by \helpref{wxThread::Create}{wxthreadcreate} or the corresponding constructors.
+
+GUI calls, such as those to a \helpref{wxWindow}{wxwindow} or 
+\helpref{wxBitmap}{wxbitmap} are explicitly not safe at all in secondary threads 
+and could end your application prematurely. This is due to several reasons,
+including the underlying native API and the fact that wxThread does not run a 
+GUI event loop similar to other APIs as MFC. 
+
+A workaround that works on some wxWidgets ports is calling \helpref{wxMutexGUIEnter}{wxmutexguienter} 
+before any GUI calls and then calling \helpref{wxMutexGUILeave}{wxmutexguileave} afterwords. However,
+the recommended way is to simply process the GUI calls in the main thread 
+through an event that is posted by either \helpref{wxPostEvent}{wxpostevent} or
+\helpref{wxEvtHandler::AddPendingEvent}{wxevthandleraddpendingevent}. This does 
+not imply that calls to these classes are thread-safe, however, as most 
+wxWidgets classes are not thread-safe, including wxString.
+
+\membersection{Don't poll a wxThread}\label{dontpollwxthread}
+
+A common problem users experience with wxThread is that in their main thread
+they will check the thread every now and then to see if it has ended through
+\helpref{wxThread::IsRunning}{wxthreadisrunning}, only to find that their 
+application has run into problems because the thread is using the default
+behavior and has already deleted itself. Naturally, they instead attempt to
+use joinable threads in place of the previous behavior.
+
+However, polling a wxThread for when it has ended is in general a bad idea -
+in fact calling a routine on any running wxThread should be avoided if 
+possible. Instead, find a way to notify yourself when the thread has ended.
+Usually you only need to notify the main thread, in which case you can post
+an event to it via \helpref{wxPostEvent}{wxpostevent} or
+\helpref{wxEvtHandler::AddPendingEvent}{wxevthandleraddpendingevent}. In 
+the case of secondary threads you can call a routine of another class
+when the thread is about to complete processing and/or set the value
+of a variable, possibly using \helpref{mutexes}{wxmutex} and/or other 
+synchronization means if necessary.
+

 \membersection{wxThread::wxThread}\label{wxthreadctor}
 
 \membersection{wxThread::wxThread}\label{wxthreadctor}
 

-\func{}{wxThread}{\void}
+\func{}{wxThread}{\param{wxThreadKind }{kind = wxTHREAD\_DETACHED}}
+
+This constructor creates a new detached (default) or joinable C++ thread object. It
+does not create or start execution of the real thread -- for this you should
+use the \helpref{Create}{wxthreadcreate} and \helpref{Run}{wxthreadrun} methods.

 
 

-Default constructor: it doesn't create nor starts the thread.
+The possible values for {\it kind} parameters are:

 
 

-\membersection{wxThread::\destruct{wxThread}}
+\twocolwidtha{7cm}
+\begin{twocollist}\itemsep=0pt
+\twocolitem{{\bf wxTHREAD\_DETACHED}}{Creates a detached thread.}
+\twocolitem{{\bf wxTHREAD\_JOINABLE}}{Creates a joinable thread.}
+\end{twocollist}
+
+
+\membersection{wxThread::\destruct{wxThread}}\label{wxthreaddtor}

 
 \func{}{\destruct{wxThread}}{\void}
 
 
 \func{}{\destruct{wxThread}}{\void}
 

-wxThread destructor is private, so you can not call it directly - i.e., deleting
-wxThread objects is forbidden. Instead, you should use \helpref{Delete}{wxthreaddelete} or
-\helpref{Kill}{wxthreadkill} methods. This also means that thread objects should
-eb {\bf always} allocated on the heap (i.e. with {\it new}) because the functions
-mentioned above will try to reclaim the storage from the heap.
+The destructor frees the resources associated with the thread. Notice that you
+should never delete a detached thread -- you may only call
+\helpref{Delete}{wxthreaddelete} on it or wait until it terminates (and auto
+destructs) itself. Because the detached threads delete themselves, they can
+only be allocated on the heap.
+
+Joinable threads should be deleted explicitly. The \helpref{Delete}{wxthreaddelete} and \helpref{Kill}{wxthreadkill} functions
+will not delete the C++ thread object. It is also safe to allocate them on
+stack.
+

 
 \membersection{wxThread::Create}\label{wxthreadcreate}
 
 
 \membersection{wxThread::Create}\label{wxthreadcreate}
 

-\func{wxThreadError}{Create}{\void}
+\func{wxThreadError}{Create}{\param{unsigned int }{stackSize = 0}}
+
+Creates a new thread. The thread object is created in the suspended state, and you
+should call \helpref{Run}{wxthreadrun} to start running it.  You may optionally
+specify the stack size to be allocated to it (Ignored on platforms that don't
+support setting it explicitly, eg. Unix system without
+\texttt{pthread\_attr\_setstacksize}). If you do not specify the stack size,
+the system's default value is used.
+
+{\bf Warning:} It is a good idea to explicitly specify a value as systems'
+default values vary from just a couple of KB on some systems (BSD and
+OS/2 systems) to one or several MB (Windows, Solaris, Linux). So, if you
+have a thread that requires more than just a few KB of memory, you will
+have mysterious problems on some platforms but not on the common ones. On the
+other hand, just indicating a large stack size by default will give you
+performance issues on those systems with small default stack since those
+typically use fully committed memory for the stack. On the contrary, if
+use a lot of threads (say several hundred), virtual adress space can get tight
+unless you explicitly specify a smaller amount of thread stack space for each
+thread.

 
 

-Creates a new thread. The thread object is created in the suspended state, you
-should call \helpref{Run}{wxthreadrun} to start running it.

 
 \wxheading{Return value}
 
 
 \wxheading{Return value}
 


@@ -56,34 +188,84 @@ One of:
 \twocolitem{{\bf wxTHREAD\_RUNNING}}{The thread is already running.}
 \end{twocollist}
 
 \twocolitem{{\bf wxTHREAD\_RUNNING}}{The thread is already running.}
 \end{twocollist}
 

+

 \membersection{wxThread::Delete}\label{wxthreaddelete}
 
 \membersection{wxThread::Delete}\label{wxthreaddelete}
 

-\func{\void}{Delete}{\void}
+\func{wxThreadError}{Delete}{\void}
+
+Calling \helpref{Delete}{wxthreaddelete} gracefully terminates a 
+detached thread, either when the thread calls \helpref{TestDestroy}{wxthreadtestdestroy} or finished processing.
+
+(Note that while this could work on a joinable thread you simply should not
+call this routine on one as afterwards you may not be able to call 
+\helpref{wxThread::Wait}{wxthreadwait} to free the memory of that thread).
+
+See \helpref{wxThread deletion}{deletionwxthread} for a broader explanation of this routine.
+
+%%FIXME: What does this return and why?
+
+\membersection{wxThread::Entry}\label{wxthreadentry}
+
+\func{virtual ExitCode}{Entry}{\void}
+
+This is the entry point of the thread. This function is pure virtual and must
+be implemented by any derived class. The thread execution will start here.
+
+The returned value is the thread exit code which is only useful for
+joinable threads and is the value returned by \helpref{Wait}{wxthreadwait}.
+
+This function is called by wxWidgets itself and should never be called
+directly.

 
 

-This function should be called to terminate this thread. Unlike \helpref{Kill}{wxthreadkill}, it
-gives the target thread the time to terminate gracefully. Because of this, however, this function
-may not return immediately and if the thread is "hung" won't return at all. Also, message processing
-is not stopped during this function execution, so the message handlers may be called from inside
-it.

 
 

-Delete() may be called for thread in any state: running, paused or even not yet created. Moreover,
-it must be called if \helpref{Create}{wxthreadcreate} or \helpref{Run}{wxthreadrun} fail to free
-the memory occupied by the thread object.
+\membersection{wxThread::Exit}\label{wxthreadexit}

 
 

-\membersection{wxThread::GetID}\label{wxthreadgetid}
+\func{void}{Exit}{\param{ExitCode }{exitcode = 0}}

 
 

-\constfunc{unsigned long}{GetID}{\void}
+This is a protected function of the wxThread class and thus can only be called
+from a derived class. It also can only be called in the context of this
+thread, i.e. a thread can only exit from itself, not from another thread.

 
 

-Gets the thread identifier: this is a platform dependent number which uniquely identifies the
+This function will terminate the OS thread (i.e. stop the associated path of
+execution) and also delete the associated C++ object for detached threads.
+\helpref{wxThread::OnExit}{wxthreadonexit} will be called just before exiting.
+
+
+\membersection{wxThread::GetCPUCount}\label{wxthreadgetcpucount}
+
+\func{static int}{GetCPUCount}{\void}
+
+Returns the number of system CPUs or -1 if the value is unknown.
+
+\wxheading{See also}
+
+\helpref{SetConcurrency}{wxthreadsetconcurrency}
+
+
+\membersection{wxThread::GetCurrentId}\label{wxthreadgetcurrentid}
+
+\func{static unsigned long}{GetCurrentId}{\void}
+
+Returns the platform specific thread ID of the current thread as a
+long.  This can be used to uniquely identify threads, even if they are
+not wxThreads.
+
+
+\membersection{wxThread::GetId}\label{wxthreadgetid}
+
+\constfunc{unsigned long}{GetId}{\void}
+
+Gets the thread identifier: this is a platform dependent number that uniquely identifies the

 thread throughout the system during its existence (i.e. the thread identifiers may be reused).
 
 thread throughout the system during its existence (i.e. the thread identifiers may be reused).
 

+

 \membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
 
 \constfunc{int}{GetPriority}{\void}
 
 Gets the priority of the thread, between zero and 100.
 
 \membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
 
 \constfunc{int}{GetPriority}{\void}
 
 Gets the priority of the thread, between zero and 100.
 

-The following priorities are already defined:
+The following priorities are defined:

 
 \twocolwidtha{7cm}
 \begin{twocollist}\itemsep=0pt
 
 \twocolwidtha{7cm}
 \begin{twocollist}\itemsep=0pt


@@ -92,29 +274,49 @@ The following priorities are already defined:
 \twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
 \end{twocollist}
 
 \twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
 \end{twocollist}
 

+

 \membersection{wxThread::IsAlive}\label{wxthreadisalive}
 
 \constfunc{bool}{IsAlive}{\void}
 
 \membersection{wxThread::IsAlive}\label{wxthreadisalive}
 
 \constfunc{bool}{IsAlive}{\void}
 

-Returns TRUE if the thread is alive (i.e. started and not terminating).
+Returns \true if the thread is alive (i.e. started and not terminating).
+
+Note that this function can only safely be used with joinable threads, not
+detached ones as the latter delete themselves and so when the real thread is
+no longer alive, it is not possible to call this function because
+the wxThread object no longer exists.
+
+\membersection{wxThread::IsDetached}\label{wxthreadisdetached}
+
+\constfunc{bool}{IsDetached}{\void}
+
+Returns \true if the thread is of the detached kind, \false if it is a joinable
+one.
+

 
 \membersection{wxThread::IsMain}\label{wxthreadismain}
 
 
 \membersection{wxThread::IsMain}\label{wxthreadismain}
 

-\constfunc{bool}{IsMain}{\void}
+\func{static bool}{IsMain}{\void}
+
+Returns \true if the calling thread is the main application thread.

 
 

-Returns TRUE if the calling thread is the main application thread.

 
 \membersection{wxThread::IsPaused}\label{wxthreadispaused}
 
 \constfunc{bool}{IsPaused}{\void}
 
 
 \membersection{wxThread::IsPaused}\label{wxthreadispaused}
 
 \constfunc{bool}{IsPaused}{\void}
 

-Returns TRUE if the thread is paused.
+Returns \true if the thread is paused.
+

 
 \membersection{wxThread::IsRunning}\label{wxthreadisrunning}
 
 \constfunc{bool}{IsRunning}{\void}
 
 
 \membersection{wxThread::IsRunning}\label{wxthreadisrunning}
 
 \constfunc{bool}{IsRunning}{\void}
 

-Returns TRUE if the thread is running.
+Returns \true if the thread is running.
+
+This method may only be safely used for joinable threads, see the remark in 
+\helpref{IsAlive}{wxthreadisalive}.
+

 
 \membersection{wxThread::Kill}\label{wxthreadkill}
 
 
 \membersection{wxThread::Kill}\label{wxthreadkill}
 


@@ -123,26 +325,64 @@ Returns TRUE if the thread is running.
 Immediately terminates the target thread. {\bf This function is dangerous and should
 be used with extreme care (and not used at all whenever possible)!} The resources
 allocated to the thread will not be freed and the state of the C runtime library
 Immediately terminates the target thread. {\bf This function is dangerous and should
 be used with extreme care (and not used at all whenever possible)!} The resources
 allocated to the thread will not be freed and the state of the C runtime library

-may become inconsistent. Use \helpref{Delete()}{wxthreaddelete} instead.
+may become inconsistent. Use \helpref{Delete()}{wxthreaddelete} for detached 
+threads or \helpref{Wait()}{wxthreadwait} for joinable threads instead.
+
+For detached threads Kill() will also delete the associated C++ object.
+However this will not happen for joinable threads and this means that you will
+still have to delete the wxThread object yourself to avoid memory leaks.
+In neither case \helpref{OnExit}{wxthreadonexit} of the dying thread will be
+called, so no thread-specific cleanup will be performed.
+
+This function can only be called from another thread context, i.e. a thread
+cannot kill itself.
+
+It is also an error to call this function for a thread which is not running or
+paused (in the latter case, the thread will be resumed first) -- if you do it,
+a {\tt wxTHREAD\_NOT\_RUNNING} error will be returned.
+

 
 \membersection{wxThread::OnExit}\label{wxthreadonexit}
 
 \func{void}{OnExit}{\void}
 
 
 \membersection{wxThread::OnExit}\label{wxthreadonexit}
 
 \func{void}{OnExit}{\void}
 

-Called when the thread exits. This function is called in the context of the thread
-associated with the wxThread object, not in the context of the main thread.
+Called when the thread exits. This function is called in the context of the
+thread associated with the wxThread object, not in the context of the main
+thread. This function will not be called if the thread was
+\helpref{killed}{wxthreadkill}.
+
+This function should never be called directly.
+
+
+\membersection{wxThread::Pause}\label{wxthreadpause}
+
+\func{wxThreadError}{Pause}{\void}
+
+Suspends the thread. Under some implementations (Win32), the thread is
+suspended immediately, under others it will only be suspended when it calls
+\helpref{TestDestroy}{wxthreadtestdestroy} for the next time (hence, if the
+thread doesn't call it at all, it won't be suspended).
+
+This function can only be called from another thread context.
+

 
 \membersection{wxThread::Run}\label{wxthreadrun}
 
 \func{wxThreadError}{Run}{\void}
 
 
 \membersection{wxThread::Run}\label{wxthreadrun}
 
 \func{wxThreadError}{Run}{\void}
 

-Runs the thread.
+Starts the thread execution. Should be called after
+\helpref{Create}{wxthreadcreate}.
+
+This function can only be called from another thread context.
+

 
 \membersection{wxThread::SetPriority}\label{wxthreadsetpriority}
 
 \func{void}{SetPriority}{\param{int}{ priority}}
 
 
 \membersection{wxThread::SetPriority}\label{wxthreadsetpriority}
 
 \func{void}{SetPriority}{\param{int}{ priority}}
 

-Sets the priority of the thread, between zero and 100. This must be set before the thread is created.
+Sets the priority of the thread, between $0$ and $100$. It can only be set
+after calling \helpref{Create()}{wxthreadcreate} but before calling
+\helpref{Run()}{wxthreadrun}.

 
 The following priorities are already defined:
 
 
 The following priorities are already defined:
 


@@ -153,29 +393,81 @@ The following priorities are already defined:
 \twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
 \end{twocollist}
 
 \twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
 \end{twocollist}
 

+

 \membersection{wxThread::Sleep}\label{wxthreadsleep}
 
 \membersection{wxThread::Sleep}\label{wxthreadsleep}
 

-\func{\void}{Sleep}{\param{unsigned long }{milliseconds}}
+\func{static void}{Sleep}{\param{unsigned long }{milliseconds}}

 
 Pauses the thread execution for the given amount of time.
 
 This function should be used instead of \helpref{wxSleep}{wxsleep} by all worker
 
 Pauses the thread execution for the given amount of time.
 
 This function should be used instead of \helpref{wxSleep}{wxsleep} by all worker

-(i.e. all except the main one) threads.
+threads (i.e. all except the main one).
+
+
+\membersection{wxThread::Resume}\label{wxthreadresume}
+
+\func{wxThreadError}{Resume}{\void}
+
+Resumes a thread suspended by the call to \helpref{Pause}{wxthreadpause}.
+
+This function can only be called from another thread context.
+
+
+\membersection{wxThread::SetConcurrency}\label{wxthreadsetconcurrency}
+
+\func{static bool}{SetConcurrency}{\param{size\_t }{level}}
+
+Sets the thread concurrency level for this process. This is, roughly, the
+number of threads that the system tries to schedule to run in parallel.
+The value of $0$ for {\it level} may be used to set the default one.
+
+Returns \true on success or false otherwise (for example, if this function is
+not implemented for this platform -- currently everything except Solaris).
+
+
+\membersection{wxThread::TestDestroy}\label{wxthreadtestdestroy}
+
+\func{virtual bool}{TestDestroy}{\void}
+
+This function should be called periodically by the thread to ensure that calls
+to \helpref{Pause}{wxthreadpause} and \helpref{Delete}{wxthreaddelete} will
+work. If it returns \true, the thread should exit as soon as possible.
+
+Notice that under some platforms (POSIX), implementation of 
+\helpref{Pause}{wxthreadpause} also relies on this function being called, so
+not calling it would prevent both stopping and suspending thread from working.
+

 
 \membersection{wxThread::This}\label{wxthreadthis}
 
 
 \membersection{wxThread::This}\label{wxthreadthis}
 

-\func{wxThread *}{This}{\void}
+\func{static wxThread *}{This}{\void}

 
 Return the thread object for the calling thread. NULL is returned if the calling thread
 is the main (GUI) thread, but \helpref{IsMain}{wxthreadismain} should be used to test
 whether the thread is really the main one because NULL may also be returned for the thread
 
 Return the thread object for the calling thread. NULL is returned if the calling thread
 is the main (GUI) thread, but \helpref{IsMain}{wxthreadismain} should be used to test
 whether the thread is really the main one because NULL may also be returned for the thread

-not created with wxThread class. Generally speaking, the return value for such thread
+not created with wxThread class. Generally speaking, the return value for such a thread

 is undefined.
 
 is undefined.
 

+

 \membersection{wxThread::Yield}\label{wxthreadyield}
 
 \membersection{wxThread::Yield}\label{wxthreadyield}
 

-\func{\void}{Yield}{\void}
+\func{void}{Yield}{\void}

 
 Give the rest of the thread time slice to the system allowing the other threads to run.
 See also \helpref{Sleep()}{wxthreadsleep}.
 
 
 Give the rest of the thread time slice to the system allowing the other threads to run.
 See also \helpref{Sleep()}{wxthreadsleep}.
 

+
+\membersection{wxThread::Wait}\label{wxthreadwait}
+
+\constfunc{ExitCode}{Wait}{\void}
+
+Gracefully terminates a joinable thread, either when the thread calls 
+\helpref{TestDestroy}{wxthreadtestdestroy} or finished processing, and 
+returns the value the thread returned from 
+\helpref{wxThread::Entry}{wxthreadentry} or {\tt (ExitCode)-1} on error. 
+
+You can only Wait() for joinable (not detached) threads.
+
+This function can only be called from another thread context.
+
+See \helpref{wxThread deletion}{deletionwxthread} for a broader explanation of this routine.