added initial version of the Doxygen manual
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51901 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
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docs/doxygen/overviews/thread.h
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docs/doxygen/overviews/thread.h
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/////////////////////////////////////////////////////////////////////////////
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// Name: thread
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// Purpose: topic overview
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// Author: wxWidgets team
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// RCS-ID: $Id$
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// Licence: wxWindows license
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/////////////////////////////////////////////////////////////////////////////
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/*!
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@page thread_overview Multithreading overview
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Classes: #wxThread, #wxMutex,
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#wxCriticalSection,
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#wxCondition
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wxWidgets provides a complete set of classes encapsulating objects necessary in
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multithreaded (MT) programs: the #thread class itself and different
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synchronization objects: #mutexes and
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@ref criticalsection_overview with
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#conditions. The thread API in wxWidgets resembles to
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POSIX1.c threads API (a.k.a. pthreads), although several functions have
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different names and some features inspired by Win32 thread API are there as
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well.
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These classes will hopefully make writing MT programs easier and they also
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provide some extra error checking (compared to the native (be it Win32 or Posix)
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thread API), however it is still a non-trivial undertaking especially for large
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projects. Before starting an MT application (or starting to add MT features to
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an existing one) it is worth asking oneself if there is no easier and safer way
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to implement the same functionality. Of course, in some situations threads
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really make sense (classical example is a server application which launches a
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new thread for each new client), but in others it might be a very poor choice
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(example: launching a separate thread when doing a long computation to show a
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progress dialog). Other implementation choices are available: for the progress
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dialog example it is far better to do the calculations in the
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@ref idleevent_overview or even simply do everything at once
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but call wxWindow::Update() periodically to update
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the screen.
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If you do decide to use threads in your application, it is strongly recommended
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that no more than one thread calls GUI functions. The thread sample shows that
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it @e is possible for many different threads to call GUI functions at once
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(all the threads created in the sample access GUI), but it is a very poor design
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choice for anything except an example. The design which uses one GUI thread and
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several worker threads which communicate with the main one using events is much
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more robust and will undoubtedly save you countless problems (example: under
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Win32 a thread can only access GDI objects such as pens, brushes, c created by
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itself and not by the other threads).
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For communication between secondary threads and the main thread, you may use
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wxEvtHandler::AddPendingEvent
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or its short version #wxPostEvent. These functions
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have a thread-safe implementation so that they can be used as they are for
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sending events from one thread to another. However there is no built in method
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to send messages to the worker threads and you will need to use the available
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synchronization classes to implement the solution which suits your needs
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yourself. In particular, please note that it is not enough to derive
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your class from #wxThread and
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#wxEvtHandler to send messages to it: in fact, this does
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not work at all.
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*/
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