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Update Multithreading Overview programming guide

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PB 2022-11-01 18:19:55 +01:00 • committed by Vadim Zeitlin
parent dd9f47d1a7
commit 41fc16489e
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docs/doxygen/overviews/thread.h
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@ -16,26 +16,21 @@
@tableofcontents
@note In the new code, it is highly recommended to use concurrency classes
provided in C++11 and newer, instead of their wxWidgets counterparts.
The warning about not using GUI classes from non-GUI threads still applies.
wxWidgets provides a complete set of classes encapsulating objects necessary in
multi-threaded (MT) applications: the wxThread class itself and different
synchronization objects: mutexes (see wxMutex) and critical sections (see
wxCriticalSection) with conditions (see wxCondition). The thread API in
wxWidgets resembles to POSIX1.c threads API (a.k.a. pthreads), although several
wxWidgets resembles to POSIX thread 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 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 an overkill. On the
other hand, the recent evolution of the computer hardware shows an important
trend towards multi-core systems, which are better exploited using multiple
threads (e.g. you may want to split a long task among as many threads as many
CPU (cores) the system reports; see wxThread::GetCPUCount).
thread API).
To implement non-blocking operations @e without using multiple threads you have
two possible implementation choices:
@ -44,8 +39,8 @@ two possible implementation choices:
- do everything at once but call wxWindow::Update() or wxApp::YieldFor(wxEVT_CATEGORY_UI)
periodically to update the screen.
If instead you choose to use threads in your application, please read the
following section of this overview.
However, it is generally much better to run time-consuming tasks in worker threads instead
of trying to work around blocked GUI (and risk reentrancy problems).
@see wxThread, wxThreadHelper, wxMutex, wxCriticalSection, wxCondition,
wxSemaphore
@ -60,9 +55,11 @@ thread and several worker threads which communicate with the main one using
@b 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, device contexts created by itself and not by the other threads).
The GUI thread is the thread in which wxWidgets was initialized, where
wxIsMainThread() returns @true.
For communication between secondary threads and the main thread, you may use
wxEvtHandler::QueueEvent or its short version ::wxQueueEvent. These functions
wxEvtHandler::QueueEvent() or its short version ::wxQueueEvent(). 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