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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 b980ab9ac6599f7f42063b71ebe6170531212780..1fe11c9e73265aa13d445ecd787ef2773b3a972d 100644 (file)
--- a/docs/latex/wx/thread.tex
+++ b/docs/latex/wx/thread.tex
@@ -1,44 +1,82 @@
 \section{\class{wxThread}}\label{wxthread}
 
 \section{\class{wxThread}}\label{wxthread}
 

-A thread is basically a path of execution through a program. Threads are also
-sometimes calls {\it light-wight processes}, but the fundamental difference
+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
 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 a leg, so careful use of synchronization objects
+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.
 
 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{wxCriticalSection}{wxarraywxcriticalsection}
+\helpref{wxMutex}{wxmutex}, \helpref{wxCondition}{wxcondition}, \helpref{wxCriticalSection}{wxcriticalsection}

 
 \latexignore{\rtfignore{\wxheading{Members}}}
 
 \membersection{wxThread::wxThread}\label{wxthreadctor}
 
 
 \latexignore{\rtfignore{\wxheading{Members}}}
 
 \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:
+
+\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}
 

-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}
 
 \func{wxThreadError}{Create}{\void}
 
 
 \membersection{wxThread::Create}\label{wxthreadcreate}
 
 \func{wxThreadError}{Create}{\void}
 

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


@@ -54,23 +92,76 @@ One of:
 
 \membersection{wxThread::Delete}\label{wxthreaddelete}
 
 
 \membersection{wxThread::Delete}\label{wxthreaddelete}
 

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

 
 

-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.
+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!

 
 

-Delete() may be called for thread in any state: running, paused or even not yet created. Moreover,
+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.
+
+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
 it must be called if \helpref{Create}{wxthreadcreate} or \helpref{Run}{wxthreadrun} fail to free

-the memory occupied by the thread object.
+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.
+
+\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.

 
 

-\membersection{wxThread::GetID}\label{wxthreadgetid}
+The returned value is the thread exit code which is only useful for
+joinable threads and is the value returned by \helpref{Wait}{wxthreadwait}.

 
 

-\constfunc{unsigned long}{GetID}{\void}
+This function is called by wxWindows itself and should never be called
+directly.

 
 

-Gets the thread identifier: this is a platform dependent number which uniquely identifies the
+\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::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}
 thread throughout the system during its existence (i.e. the thread identifiers may be reused).
 
 \membersection{wxThread::GetPriority}\label{wxthreadgetpriority}


@@ -79,7 +170,7 @@ thread throughout the system during its existence (i.e. the thread identifiers m
 
 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


@@ -94,9 +185,15 @@ The following priorities are already defined:
 
 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).
 

+\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.
 


@@ -121,18 +218,57 @@ be used with extreme care (and not used at all whenever possible)!} The resource
 allocated to the thread will not be freed and the state of the C runtime library
 may become inconsistent. Use \helpref{Delete()}{wxthreaddelete} instead.
 
 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. 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}
+
+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:
 


@@ -145,26 +281,64 @@ The following priorities are already defined:
 
 \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{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}
 
 
 \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.
 
 \membersection{wxThread::Yield}\label{wxthreadyield}
 
 is undefined.
 
 \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}
+
+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.
+