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Creating User-Interface Threads in MFC |
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| To create a user-interface thread, first derive a class from CWinThread and
implement the class using the DECLARE_DYNCREATE and IMPLEMENT_DYNCREATE in the
.h and .cpp file respectively. We can override the functions in the derived
class, but it should be noted that, it is mandatory to override the following
functions. 1. ExitIntstance This is the clean up function for the object when the thread terminates. 2. InitInstance Perform the thread based initialization. 3. OnIdle This is used to perform the thread specific idle time processing. 4. PreTranslateMessage This can be used to filter messages before they are dispatched to TranslateMessage and DispatchMessage. 5. ProcessWndProcException This function can be used to intercept unhandled exceptions thrown by the thread’s message and command handlers. 6. Run This is the controlling function of the thread and it contains the message pump. The thread creation is actually achieved using the AfxBeginThread function and MFC provide two overloaded versions of this function. One of them is used for creating user-interface threads and the other for creating worker threads. The user-interface version of AfxBeginThread takes these parameters 1. The RUNTIME_CLASS structure of the class we derived from CWinThread 2. Thread Priority Level which is optional and the default are normal priority. 3. Desired Stack size of the thread (optional). By default its the same as the creator stack size. 4. Thread State which is optional. By default it is CREATE_SUSPENDED 5. Security Attributes of the thread (Optional). By default it’s the same as the creator. Example: CWinThread* AfxBeginThread ( CRuntimeClass* pUserThread, int nPriority = THREAD_PRIORITY_NORMAL, UINT nStackSize = 0, DWORD dwCreateFlags = 0, LPSECURITY_ATTRIBUTES lpSecurityAttrs = NULL); The return value will be a pointer to the newly created Thread object and NULL if it fails. To terminate a thread call the AfxEndThread from with in the thread or return from the controlling function in case of a worker thread. |
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| RELATED TOPICS | |||
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What is a thread? Thread Pools Multithreading Thread Vs Process MultiThreading support in C++ and MFC Creating worker Threads in MFC Terminating Threads Thread Synchronization Designing a Thread-safe class Semaphore in MFC Mutex in MFC Critical Section in MFC Event Objects in MFC CSingleLock and CMultiLock in MFC |
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