+ By default wxThreads in wxWidgets use the @b detached behaviour.
+ Detached threads delete themselves once they have completed, either by themselves
+ when they complete processing or through a call to Delete(), and thus
+ @b must be created on the heap (through the new operator, for example).
+
+ Typically you'll want to store the instances of the detached wxThreads you
+ allocate, so that you can call functions on them.
+ Because of their nature however you'll need to always use a critical section
+ when accessing them:
+
+ @code
+ // declare a new type of event, to be used by our MyThread class:
+ wxDECLARE_EVENT(wxEVT_COMMAND_MYTHREAD_COMPLETED, wxThreadEvent);
+ wxDECLARE_EVENT(wxEVT_COMMAND_MYTHREAD_UPDATE, wxThreadEvent);
+ class MyFrame;
+
+ class MyThread : public wxThread
+ {
+ public:
+ MyThread(MyFrame *handler)
+ : wxThread(wxTHREAD_DETACHED)
+ { m_pHandler = handler }
+ ~MyThread();
+
+ protected:
+ virtual ExitCode Entry();
+ MyFrame *m_pHandler;
+ };
+
+ class MyFrame : public wxFrame
+ {
+ public:
+ ...
+ ~MyFrame()
+ {
+ // it's better to do any thread cleanup in the OnClose()
+ // event handler, rather than in the destructor.
+ // This is because the event loop for a top-level window is not
+ // active anymore when its destructor is called and if the thread
+ // sends events when ending, they won't be processed unless
+ // you ended the thread from OnClose.
+ // See @ref overview_windowdeletion for more info.
+ }
+ ...
+ void DoStartThread();
+ void DoPauseThread();
+
+ // a resume routine would be nearly identic to DoPauseThread()
+ void DoResumeThread() { ... }
+
+ void OnThreadUpdate(wxThreadEvent&);
+ void OnThreadCompletion(wxThreadEvent&);
+ void OnClose(wxCloseEvent&);
+
+ protected:
+ MyThread *m_pThread;
+ wxCriticalSection m_pThreadCS; // protects the m_pThread pointer
+
+ wxDECLARE_EVENT_TABLE();
+ };
+
+ wxBEGIN_EVENT_TABLE(MyFrame, wxFrame)
+ EVT_CLOSE(MyFrame::OnClose)
+ EVT_MENU(Minimal_Start, MyFrame::DoStartThread)
+ EVT_COMMAND(wxID_ANY, wxEVT_COMMAND_MYTHREAD_UPDATE, MyFrame::OnThreadUpdate)
+ EVT_COMMAND(wxID_ANY, wxEVT_COMMAND_MYTHREAD_COMPLETED, MyFrame::OnThreadCompletion)
+ wxEND_EVENT_TABLE()
+
+ wxDEFINE_EVENT(wxEVT_COMMAND_MYTHREAD_COMPLETED, wxThreadEvent)
+ wxDEFINE_EVENT(wxEVT_COMMAND_MYTHREAD_UPDATE, wxThreadEvent)
+
+ void MyFrame::DoStartThread()
+ {
+ m_pThread = new MyThread(this);
+
+ if ( m_pThread->Run() != wxTHREAD_NO_ERROR )
+ {
+ wxLogError("Can't create the thread!");
+ delete m_pThread;
+ m_pThread = NULL;
+ }
+
+ // after the call to wxThread::Run(), the m_pThread pointer is "unsafe":
+ // at any moment the thread may cease to exist (because it completes its work).
+ // To avoid dangling pointers OnThreadExit() will set m_pThread
+ // to NULL when the thread dies.
+ }
+
+ wxThread::ExitCode MyThread::Entry()
+ {
+ while (!TestDestroy())
+ {
+ // ... do a bit of work...
+
+ wxQueueEvent(m_pHandler, new wxThreadEvent(wxEVT_COMMAND_MYTHREAD_UPDATE));
+ }
+
+ // signal the event handler that this thread is going to be destroyed
+ // NOTE: here we assume that using the m_pHandler pointer is safe,
+ // (in this case this is assured by the MyFrame destructor)
+ wxQueueEvent(m_pHandler, new wxThreadEvent(wxEVT_COMMAND_MYTHREAD_COMPLETED));
+
+ return (wxThread::ExitCode)0; // success
+ }
+
+ MyThread::~MyThread()
+ {
+ wxCriticalSectionLocker enter(m_pHandler->m_pThreadCS);
+
+ // the thread is being destroyed; make sure not to leave dangling pointers around
+ m_pHandler->m_pThread = NULL;
+ }
+
+ void MyFrame::OnThreadCompletion(wxThreadEvent&)
+ {
+ wxMessageOutputDebug().Printf("MYFRAME: MyThread exited!\n");
+ }
+
+ void MyFrame::OnThreadUpdate(wxThreadEvent&)
+ {
+ wxMessageOutputDebug().Printf("MYFRAME: MyThread update...\n");
+ }
+
+ void MyFrame::DoPauseThread()
+ {
+ // anytime we access the m_pThread pointer we must ensure that it won't
+ // be modified in the meanwhile; since only a single thread may be
+ // inside a given critical section at a given time, the following code
+ // is safe:
+ wxCriticalSectionLocker enter(m_pThreadCS);
+
+ if (m_pThread) // does the thread still exist?
+ {
+ // without a critical section, once reached this point it may happen
+ // that the OS scheduler gives control to the MyThread::Entry() function,
+ // which in turn may return (because it completes its work) making
+ // invalid the m_pThread pointer
+
+ if (m_pThread->Pause() != wxTHREAD_NO_ERROR )
+ wxLogError("Can't pause the thread!");
+ }
+ }
+
+ void MyFrame::OnClose(wxCloseEvent&)
+ {
+ {
+ wxCriticalSectionLocker enter(m_pThreadCS);
+
+ if (m_pThread) // does the thread still exist?
+ {
+ wxMessageOutputDebug().Printf("MYFRAME: deleting thread");
+
+ if (m_pThread->Delete() != wxTHREAD_NO_ERROR )
+ wxLogError("Can't delete the thread!");
+ }
+ } // exit from the critical section to give the thread
+ // the possibility to enter its destructor
+ // (which is guarded with m_pThreadCS critical section!)
+
+ while (1)
+ {
+ { // was the ~MyThread() function executed?
+ wxCriticalSectionLocker enter(m_pThreadCS);
+ if (!m_pThread) break;
+ }
+
+ // wait for thread completion
+ wxThread::This()->Sleep(1);
+ }
+
+ Destroy();
+ }
+ @endcode
+
+ For a more detailed and comprehensive example, see @sample{thread}.
+ For a simpler way to share data and synchronization objects between
+ the main and the secondary thread see wxThreadHelper.
+
+ Conversely, @b joinable threads do not delete themselves when they are done
projects / wxWidgets.git / blobdiff