36c9828f70
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51911 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
62 lines
3.1 KiB
C
62 lines
3.1 KiB
C
/////////////////////////////////////////////////////////////////////////////
|
|
// Name: thread
|
|
// Purpose: topic overview
|
|
// Author: wxWidgets team
|
|
// RCS-ID: $Id$
|
|
// Licence: wxWindows license
|
|
/////////////////////////////////////////////////////////////////////////////
|
|
|
|
/*!
|
|
|
|
@page thread_overview Multithreading overview
|
|
|
|
Classes: #wxThread, #wxMutex,
|
|
#wxCriticalSection,
|
|
#wxCondition
|
|
wxWidgets provides a complete set of classes encapsulating objects necessary in
|
|
multithreaded (MT) programs: the #thread class itself and different
|
|
synchronization objects: #mutexes and
|
|
@ref criticalsection_overview with
|
|
#conditions. The thread API in wxWidgets 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 a 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
|
|
@ref idleevent_overview or even simply do everything at once
|
|
but call wxWindow::Update() 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 @e 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 secondary threads and the main thread, you may use
|
|
wxEvtHandler::AddPendingEvent
|
|
or its short version #wxPostEvent. These functions
|
|
have a thread-safe implementation so that they can be used as they are for
|
|
sending events from one thread to another. However there is no built in method
|
|
to send messages to the worker threads and you will need to use the available
|
|
synchronization classes to implement the solution which suits your needs
|
|
yourself. In particular, please note that it is not enough to derive
|
|
your class from #wxThread and
|
|
#wxEvtHandler to send messages to it: in fact, this does
|
|
not work at all.
|
|
|
|
*/
|
|
|
|
|