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

diff --git a/docs/latex/wx/thread.tex b/docs/latex/wx/thread.tex
index b487d8178bbf19380a624352631c3a5fcc73c99c..1559443b695d7ab865b5db72da3da6bafb7b8192 100644 (file)
--- a/docs/latex/wx/thread.tex
+++ b/docs/latex/wx/thread.tex
@@ -1,13 +1,35 @@
 \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
 separated while all threads share the same address space. While it makes it
 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
+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} and/or \helpref{critical sections}{wxcriticalsection} is recommended.
 
 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.
 

+There are two types of threads in wxWidgets: {\it detached} and {\it joinable}
+ones, just as in the POSIX thread API (but unlike Win32 threads where all threads
+are joinable). The difference between the two is that only joinable threads
+can return a return code -- this is returned by the Wait() function. Detached
+threads (the default type) cannot be waited for.
+
+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. 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.
+
+This means, of course, that all detached threads {\bf must} be created on the
+heap because the thread will call {\tt delete this;} upon termination. Joinable
+threads may be created on the stack although more usually they will be created
+on the heap as well. Don't create global thread objects because they allocate
+memory in their constructor, which will cause problems for the memory checking
+system. Finally, another consequence of the handling of the above is that you
+should never delete a detached thread yourself, as this will be done by the
+thread itself when it terminates.
+

 \wxheading{Derived from}
 
 None.
 \wxheading{Derived from}
 
 None.


@@ -22,35 +44,47 @@ None.
 
 \latexignore{\rtfignore{\wxheading{Members}}}
 
 
 \latexignore{\rtfignore{\wxheading{Members}}}
 

+

 \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.
+
+The possible values for {\it kind} parameters are:
+
+\twocolwidtha{7cm}
+\begin{twocollist}\itemsep=0pt
+\twocolitem{{\bf wxTHREAD\_DETACHED}}{Create a detached thread.}
+\twocolitem{{\bf wxTHREAD\_JOINABLE}}{Create a joinable thread}
+\end{twocollist}

 
 

-Constructor creates a new detached (default) or joinable C++ thread object. It
-does not create (or starts execution of) the real thread - for this you should
-use \helpref{Create}{wxthreadcreate} and \helpref{Run}{wxthreadrun} methods.

 
 

-\membersection{wxThread::\destruct{wxThread}}
+\membersection{wxThread::\destruct{wxThread}}\label{wxthreaddtor}

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

-Destructor frees the ressources associated with the thread. Notice that you
-should never delete a detached thread - you may only call 
+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.
 
 \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.
 

-The joinable threads, however, may and should be deleted explicitly and 
-\helpref{Delete}{wxthreaddelete} and \helpref{Kill}{wxthreadkill} functions
+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.
 
 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, you
-should call \helpref{Run}{wxthreadrun} to start running it.
+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).

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


@@ -63,6 +97,7 @@ 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}
 
 \func{void}{Delete}{\void}
 \membersection{wxThread::Delete}\label{wxthreaddelete}
 
 \func{void}{Delete}{\void}


@@ -70,25 +105,27 @@ One of:
 Calling \helpref{Delete}{wxthreaddelete} is a graceful way to terminate the
 thread. It asks the thread to terminate and, if the thread code is well
 written, the thread will terminate after the next call to 
 Calling \helpref{Delete}{wxthreaddelete} is a graceful way to terminate the
 thread. It asks the thread to terminate and, if the thread code is well
 written, the thread will terminate after the next call to 

-\helpref{TestDestroy}{wxthreadtestdestroy} which should happen quiet soon.
+\helpref{TestDestroy}{wxthreadtestdestroy} which should happen quite soon.

 
 

-However, if the thread doesn't call \helpref{TestDestroy}{wxthreadtestdestroy} 
+However, if the thread doesn't call \helpref{TestDestroy}{wxthreadtestdestroy}

 often enough (or at all), the function will not return immediately, but wait
 often enough (or at all), the function will not return immediately, but wait

-until the thread terminates. As it may take a long time, the message processing
-is not stopped during this function execution, so the message handlers may be
+until the thread terminates. As it may take a long time, and the message processing
+is not stopped during this function execution, message handlers may be

 called from inside it!
 
 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} failed for a detached thread to free the memory
-occupied by the thread object (it will be done in the destructor for joinable
-threads).
+Delete() may be called for a 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 in order to free the memory occupied by the
+thread object. However, you should not call Delete() on a detached thread which
+already terminated -- doing so will probably result in a crash because the
+thread object doesn't exist any more.

 
 For detached threads Delete() will also delete the C++ thread object, but it
 will not do this for joinable ones.
 
 This function can only be called from another thread context.
 
 
 For detached threads Delete() will also delete the C++ thread object, but it
 will not do this for joinable ones.
 
 This function can only be called from another thread context.
 

+

 \membersection{wxThread::Entry}\label{wxthreadentry}
 
 \func{virtual ExitCode}{Entry}{\void}
 \membersection{wxThread::Entry}\label{wxthreadentry}
 
 \func{virtual ExitCode}{Entry}{\void}


@@ -96,19 +133,54 @@ This function can only be called from another thread context.
 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.
 
 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 the
+The returned value is the thread exit code which is only useful for

 joinable threads and is the value returned by \helpref{Wait}{wxthreadwait}.
 
 joinable threads and is the value returned by \helpref{Wait}{wxthreadwait}.
 

-This function is called by wxWindows itself and should never be called
+This function is called by wxWidgets itself and should never be called

 directly.
 
 directly.
 

+
+\membersection{wxThread::Exit}\label{wxthreadexit}
+
+\func{void}{Exit}{\param{ExitCode }{exitcode = 0}}
+
+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.
+
+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}
 
 \membersection{wxThread::GetId}\label{wxthreadgetid}
 
 \constfunc{unsigned long}{GetId}{\void}
 

-Gets the thread identifier: this is a platform dependent number which uniquely identifies the
+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}
 \membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
 
 \constfunc{int}{GetPriority}{\void}


@@ -124,35 +196,49 @@ The following priorities are 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}
 
 
 \membersection{wxThread::IsDetached}\label{wxthreadisdetached}
 
 \constfunc{bool}{IsDetached}{\void}
 

-Returns TRUE if the thread is of detached kind, FALSE if it is a joinable one.
+Returns \true if the thread is of the detached kind, \false if it is a joinable
+one.
+

 
 \membersection{wxThread::IsMain}\label{wxthreadismain}
 
 \func{static bool}{IsMain}{\void}
 
 
 \membersection{wxThread::IsMain}\label{wxthreadismain}
 
 \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}
 


@@ -164,43 +250,60 @@ allocated to the thread will not be freed and the state of the C runtime library
 may become inconsistent. Use \helpref{Delete()}{wxthreaddelete} instead.
 
 For detached threads Kill() will also delete the associated C++ object.
 may become inconsistent. Use \helpref{Delete()}{wxthreaddelete} 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.

 
 

-This function can only be called from another thread context.

 
 \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.
 
 
 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
 \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 
+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.
 
 \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}
 

-Starts the thread execution. Should be called after 
+Starts the thread execution. Should be called after

 \helpref{Create}{wxthreadcreate}.
 
 This function can only be called from another thread context.
 
 \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:
 


@@ -211,6 +314,7 @@ 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}
 
 \func{static void}{Sleep}{\param{unsigned long }{milliseconds}}
 \membersection{wxThread::Sleep}\label{wxthreadsleep}
 
 \func{static void}{Sleep}{\param{unsigned long }{milliseconds}}


@@ -218,7 +322,8 @@ The following priorities are already defined:
 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}
 
 
 \membersection{wxThread::Resume}\label{wxthreadresume}
 


@@ -228,13 +333,31 @@ Resumes a thread suspended by the call to \helpref{Pause}{wxthreadpause}.
 
 This function can only be called from another thread context.
 
 
 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}
 
 \membersection{wxThread::TestDestroy}\label{wxthreadtestdestroy}
 

-\func{bool}{TestDestroy}{\void}
+\func{virtual bool}{TestDestroy}{\void}

 
 

-This function should be periodically called by the thread to ensure that calls
+This function should be called periodically by the thread to ensure that calls

 to \helpref{Pause}{wxthreadpause} and \helpref{Delete}{wxthreaddelete} will
 to \helpref{Pause}{wxthreadpause} and \helpref{Delete}{wxthreaddelete} will

-work. If it returns TRUE, the thread should exit as soon as possible.
+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}
 


@@ -243,9 +366,10 @@ work. If it returns TRUE, the thread should exit as soon as possible.
 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}
 
 \func{void}{Yield}{\void}
 \membersection{wxThread::Yield}\label{wxthreadyield}
 
 \func{void}{Yield}{\void}


@@ -253,13 +377,14 @@ is undefined.
 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}
 
 \membersection{wxThread::Wait}\label{wxthreadwait}
 
 \constfunc{ExitCode}{Wait}{\void}
 

-Waits until the thread terminates and returns its exit code or {\tt
-(ExitCode)-1} on error.
+Waits until the thread terminates and returns its exit code 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.
 
 You can only Wait() for joinable (not detached) threads.
 
 This function can only be called from another thread context.

+