f6bcfd974e
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@7748 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
47 lines
2.6 KiB
TeX
47 lines
2.6 KiB
TeX
\section{Multithreading overview}\label{wxthreadoverview}
|
|
|
|
Classes: \helpref{wxThread}{wxthread}, \helpref{wxMutex}{wxmutex},
|
|
\helpref{wxCriticalSection}{wxcriticalsection},
|
|
\helpref{wxCondition}{wxcondition}
|
|
|
|
wxWindows provides a complete set of classes encapsulating objects necessary in
|
|
multithreaded (MT) programs: the \helpref{thread}{wxthread} class itself and different
|
|
synchronization objects: \helpref{mutexes}{wxmutex} and
|
|
\helpref{critical sections}{wxcriticalsection} with
|
|
\helpref{conditions}{wxcondition}. The thread API in wxWindows resembles to
|
|
POSIX1.c threads API (a.k.a. pthreads), although several functions have
|
|
different names and some features inspired by Win32 thread API are there as
|
|
well.
|
|
|
|
These classes will hopefully make writing MT programs easier and they also
|
|
provide some extra error checking (compared to the native (be it Win32 or Posix)
|
|
thread API), however it is still an non-trivial undertaking especially for large
|
|
projects. Before starting an MT application (or starting to add MT features to
|
|
an existing one) it is worth asking oneself if there is no easier and safer way
|
|
to implement the same functionality. Of course, in some situations threads
|
|
really make sense (classical example is a server application which launches a
|
|
new thread for each new client), but in others it might be a very poor choice
|
|
(example: launching a separate thread when doing a long computation to show a
|
|
progress dialog). Other implementation choices are available: for the progress
|
|
dialog example it is far better to do the calculations in the
|
|
\helpref{idle handler}{wxidleevent} or call \helpref{wxYield()}{wxyield}
|
|
periodically to update the screen.
|
|
|
|
If you do decide to use threads in your application, it is strongly recommended
|
|
that no more than one thread calls GUI functions. The thread sample shows that
|
|
it {\it is} possible for many different threads to call GUI functions at once
|
|
(all the threads created in the sample access GUI), but it is a very poor design
|
|
choice for anything except an example. The design which uses one GUI thread and
|
|
several worker threads which communicate with the main one using events is much
|
|
more robust and will undoubtedly save you countless problems (example: under
|
|
Win32 a thread can only access GDI objects such as pens, brushes, \&c created by
|
|
itself and not by the other threads).
|
|
|
|
For communication between threads, use
|
|
\helpref{wxEvtHandler::AddPendingEvent}{wxevthandleraddpendingevent}
|
|
or its short version \helpref{wxPostEvent}{wxpostevent}. These functions
|
|
have thread safe implementation so that they can be used as they are for
|
|
sending event from one thread to another.
|
|
|
|
|