\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 also
+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 POSIX thread API (but unlike Win32 threads where all threads
+are joinable). The difference between the two is that only joinbale threads
+can return a return code - it is returned by Wait() function. The detached
+threads (default) can not 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 of the
+system resources used by it will never be freed and you also must delete the
+corresponding wxThread object yourself, while 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. The
+joinable threads may be created on stack (don't create global thread objects
+because they allocate memory in their constructor which is a badthing to do),
+although usually they will be created on the heap as well.
\wxheading{Derived from}
None.
+\wxheading{Include files}
+
+<wx/thread.h>
+
\wxheading{See also}
-\helpref{wxMutex}{wxmutex}, \helpref{wxCondition}{wxcondition}
+\helpref{wxMutex}{wxmutex}, \helpref{wxCondition}{wxcondition}, \helpref{wxCriticalSection}{wxcriticalsection}
\latexignore{\rtfignore{\wxheading{Members}}}
-\membersection{wxThread::wxThread}\label{wxthreadconstr}
+\membersection{wxThread::wxThread}\label{wxthreadctor}
\func{}{wxThread}{\void}
-Default constructor.
+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}}
\func{}{\destruct{wxThread}}{\void}
-Destroys the wxThread object.
+Destructor frees the ressources 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.
+
+The joinable threads, however, may and should be deleted explicitly and
+\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}
-Creates a thread control.
+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}
\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}
-\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 quiet 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, the message processing
+is not stopped during this function execution, so the 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 (it will be done in the destructor for joinable
+threads).
-Destroys the thread immediately unless the application has specified deferral via \helpref{wxThread::DeferDestroy}{wxthreaddeferdestroy}.
+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. 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 the
+joinable threads and is the value returned by \helpref{Wait}{wxthreadwait}.
-\membersection{wxThread::GetID}\label{wxthreadgetid}
+This function is called by wxWindows itself and should never be called
+directly.
-\constfunc{unsigned long}{GetID}{\void}
+\membersection{wxThread::GetId}\label{wxthreadgetid}
-Gets the thread identifier.
+\constfunc{unsigned long}{GetId}{\void}
+
+Gets the thread identifier: this is a platform dependent number which uniquely identifies the
+thread throughout the system during its existence (i.e. the thread identifiers may be reused).
\membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
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
\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 detached kind, FALSE if it is a joinable one.
\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}
-Returns TRUE if the thread is the main application thread.
+\constfunc{bool}{IsRunning}{\void}
-\membersection{wxThread::Join}\label{wxthreadjoin}
+Returns TRUE if the thread is running.
-\func{void*}{Join}{\void}
+\membersection{wxThread::Kill}\label{wxthreadkill}
-Waits for the termination of the thread. Returns a platform-specific exit code. TODO
+\func{wxThreadError}{Kill}{\void}
+
+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.
+
+This function can only be called from another thread context.
\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 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}
\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
+(i.e. all except the main one) threads.
+
+\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::TestDestroy}\label{wxthreadtestdestroy}
+
+\func{bool}{TestDestroy}{\void}
+
+This function should be periodically called 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 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.
-%%% Local Variables:
-%%% mode: latex
-%%% TeX-master: "referenc"
-%%% End:
+This function can only be called from another thread context.
projects / wxWidgets.git / blobdiff