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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 fab79009fcdfd8def027547ff6165720bdd5a6ef..1fe11c9e73265aa13d445ecd787ef2773b3a972d 100644 (file)
--- a/docs/latex/wx/thread.tex
+++ b/docs/latex/wx/thread.tex
@@ -1,34 +1,83 @@
 \section{\class{wxThread}}\label{wxthread}
 
 \section{\class{wxThread}}\label{wxthread}
 

-A wxThread manages a system thread, code which executes as a mini-process within the application.
+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
+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.
+
+There are two types of threads in wxWindows: {\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.

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

+\wxheading{Include files}
+
+<wx/thread.h>
+

 \wxheading{See also}
 
 \wxheading{See also}
 

-\helpref{wxMutex}{wxmutex}, \helpref{wxCondition}{wxcondition}
+\helpref{wxMutex}{wxmutex}, \helpref{wxCondition}{wxcondition}, \helpref{wxCriticalSection}{wxcriticalsection}

 
 \latexignore{\rtfignore{\wxheading{Members}}}
 
 
 \latexignore{\rtfignore{\wxheading{Members}}}
 

-\membersection{wxThread::wxThread}\label{wxthreadconstr}
+\membersection{wxThread::wxThread}\label{wxthreadctor}
+
+\func{}{wxThread}{\param{wxThreadKind }{kind = wxTHREAD\_DETACHED}}

 
 

-\func{}{wxThread}{\void}
+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.
+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}

 
 \membersection{wxThread::\destruct{wxThread}}
 
 \func{}{\destruct{wxThread}}{\void}
 
 
 \membersection{wxThread::\destruct{wxThread}}
 
 \func{}{\destruct{wxThread}}{\void}
 

-Destroys the wxThread object.
+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}
 
 \func{wxThreadError}{Create}{\void}
 
 
 \membersection{wxThread::Create}\label{wxthreadcreate}
 
 \func{wxThreadError}{Create}{\void}
 

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

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


@@ -36,39 +85,84 @@ One of:
 
 \twocolwidtha{7cm}
 \begin{twocollist}\itemsep=0pt
 
 \twocolwidtha{7cm}
 \begin{twocollist}\itemsep=0pt

-\twocolitem{{\bf THREAD\_NO\_ERROR}}{There was no error.}
-\twocolitem{{\bf THREAD\_NO\_RESOURCE}}{There were insufficient resources to create a new thread.}
-\twocolitem{{\bf THREAD\_RUNNING}}{The thread is already running.}
+\twocolitem{{\bf wxTHREAD\_NO\_ERROR}}{There was no error.}
+\twocolitem{{\bf wxTHREAD\_NO\_RESOURCE}}{There were insufficient resources to create a new thread.}
+\twocolitem{{\bf wxTHREAD\_RUNNING}}{The thread is already running.}

 \end{twocollist}
 
 \end{twocollist}
 

-\membersection{wxThread::DeferDestroy}\label{wxthreaddeferdestroy}
+\membersection{wxThread::Delete}\label{wxthreaddelete}

 
 

-\func{void}{DeferDestroy}{\param{bool}{ defer}}
+\func{void}{Delete}{\void}

 
 

-If {\it defer} is TRUE, defers thread destruction. This function affects the
-calling thread.
+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 quite soon.

 
 

-\membersection{wxThread::Destroy}\label{wxthreaddestroy}
+However, if the thread doesn't call \helpref{TestDestroy}{wxthreadtestdestroy} 
+often enough (or at all), the function will not return immediately, but wait
+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!

 
 

-\func{wxThreadError}{Destroy}{\void}
+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. This cleanup will be done in the destructor for joinable
+threads.

 
 

-Destroys the thread immediately unless the application has specified deferral via \helpref{wxThread::DeferDestroy}{deferdestroy}.
+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 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.

 
 

-\wxheading{Return value}
+For detached threads Delete() will also delete the C++ thread object, but it
+will not do this for joinable ones.

 
 

-One of:
+This function can only be called from another thread context.

 
 

-\twocolwidtha{7cm}
-\begin{twocollist}\itemsep=0pt
-\twocolitem{{\bf THREAD\_NO\_ERROR}}{There was no error.}
-\twocolitem{{\bf THREAD\_NOT\_RUNNING}}{The thread is not running.}
-\end{twocollist}
+\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 wxWindows itself and should never be called
+directly.
+
+\membersection{wxThread::Exit}\label{wxthreadexit}
+
+\func{void}{Exit}{\param{ExitCode }{exitcode = 0}}

 
 

-\membersection{wxThread::GetID}\label{wxthreadgetid}
+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.

 
 

-\constfunc{unsigned long}{GetID}{\void}
+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.

 
 

-Gets the thread identifier.
+\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::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).

 
 \membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
 
 
 \membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
 


@@ -76,7 +170,7 @@ Gets the thread identifier.
 
 Gets the priority of the thread, between zero and 100.
 
 
 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


@@ -89,31 +183,92 @@ The following priorities are already defined:
 
 \constfunc{bool}{IsAlive}{\void}
 
 
 \constfunc{bool}{IsAlive}{\void}
 

-Returns TRUE if the thread is alive.
+Returns TRUE if the thread is alive (i.e. started and not terminating).
+
+\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.
+
+\membersection{wxThread::IsPaused}\label{wxthreadispaused}
+
+\constfunc{bool}{IsPaused}{\void}
+
+Returns TRUE if the thread is paused.
+
+\membersection{wxThread::IsRunning}\label{wxthreadisrunning}
+
+\constfunc{bool}{IsRunning}{\void}

 
 

-Returns TRUE if the thread is the main application thread.
+Returns TRUE if the thread is running.

 
 

-\membersection{wxThread::Join}\label{wxthreadjoin}
+\membersection{wxThread::Kill}\label{wxthreadkill}

 
 

-\func{void*}{Join}{\void}
+\func{wxThreadError}{Kill}{\void}

 
 

-Waits for the termination of the thread. Returns a platform-specific exit code. TODO
+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.
+
+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. The default implementation calls \helpref{wxThread::Join}{wxthreadjoin}.
+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}
+
+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:
 


@@ -124,8 +279,66 @@ 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}}
+
+Pauses the thread execution for the given amount of time.
+
+This function should be used instead of \helpref{wxSleep}{wxsleep} by all worker
+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{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.
+
+\membersection{wxThread::This}\label{wxthreadthis}
+
+\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
+not created with wxThread class. Generally speaking, the return value for such a thread
+is undefined.
+
+\membersection{wxThread::Yield}\label{wxthreadyield}
+
+\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}.
+
+\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.
+
+You can only Wait() for joinable (not detached) threads.
+
+This function can only be called from another thread context.

 
 

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