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.
-There are two types of threads in wxWindows: {\it detached} and {\it joinable}
+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
+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
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.
+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}
\latexignore{\rtfignore{\wxheading{Members}}}
+
\membersection{wxThread::wxThread}\label{wxthreadctor}
\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
+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:
\twocolitem{{\bf wxTHREAD\_JOINABLE}}{Create a joinable thread}
\end{twocollist}
-\membersection{wxThread::\destruct{wxThread}}
+
+\membersection{wxThread::\destruct{wxThread}}\label{wxthreaddtor}
\func{}{\destruct{wxThread}}{\void}
The destructor frees the resources associated with the thread. Notice that you
-should never delete a detached thread - you may only call
+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.
will not delete the C++ thread object. It is also safe to allocate them on
stack.
+
\membersection{wxThread::Create}\label{wxthreadcreate}
\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).
+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.
+
\wxheading{Return value}
\twocolitem{{\bf wxTHREAD\_RUNNING}}{The thread is already running.}
\end{twocollist}
+
\membersection{wxThread::Delete}\label{wxthreaddelete}
\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
+written, the thread will terminate after the next call to
\helpref{TestDestroy}{wxthreadtestdestroy} which should happen quite soon.
However, if the thread doesn't call \helpref{TestDestroy}{wxthreadtestdestroy}
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, 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
-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.
+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.
+
\membersection{wxThread::Entry}\label{wxthreadentry}
\func{virtual ExitCode}{Entry}{\void}
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
+This function is called by wxWidgets itself and should never be called
directly.
+
\membersection{wxThread::Exit}\label{wxthreadexit}
\func{void}{Exit}{\param{ExitCode }{exitcode = 0}}
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}
\helpref{SetConcurrency}{wxthreadsetconcurrency}
+
\membersection{wxThread::GetCurrentId}\label{wxthreadgetcurrentid}
\func{static unsigned long}{GetCurrentId}{\void}
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).
+
\membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
\constfunc{int}{GetPriority}{\void}
\twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
\end{twocollist}
+
\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.
+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}
-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}
-Returns true if the thread is paused.
+Returns \true if the thread is paused.
+
\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}
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,
+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}
This function should never be called directly.
+
\membersection{wxThread::Pause}\label{wxthreadpause}
\func{wxThreadError}{Pause}{\void}
This function can only be called from another thread context.
+
\membersection{wxThread::Run}\label{wxthreadrun}
\func{wxThreadError}{Run}{\void}
This function can only be called from another thread context.
+
\membersection{wxThread::SetPriority}\label{wxthreadsetpriority}
\func{void}{SetPriority}{\param{int}{ priority}}
\twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
\end{twocollist}
+
\membersection{wxThread::Sleep}\label{wxthreadsleep}
\func{static void}{Sleep}{\param{unsigned long }{milliseconds}}
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}
This function can only be called from another thread context.
+
\membersection{wxThread::SetConcurrency}\label{wxthreadsetconcurrency}
\func{static bool}{SetConcurrency}{\param{size\_t }{level}}
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).
+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}
+\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.
+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}
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}
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