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Getting benefit of WaitForMultiple Object?

WaitForMultipleObject could be used to synchronize the calls/events. Let take an example, we have to print something; we need a document and printer should be ready to take job. Now for document printer to print same document need to satisfy above two conditions, document must be present and printer should be ready, then only it could start the printing job. So, document printing application must wait till both of condition satisfies, i.e. it waits for event. Here we can utilize WaitForMultipleObject, it  could help the mainthread to wait till other event is complete.

Main Thread:-

  hEvent[0] = CreateEvent(NULL,FALSE,FALSE,"EVENTONE");
  hEvent[1] = CreateEvent(NULL,FALSE,FALSE,"EVENTTWO");
  // our two worker thread, who will set event for main event:-
  AfxBeginThread(LpThreadWorker,(LPVOID)hEvent[0]);
  AfxBeginThread(LpThreadWorker,(LPVOID)hEvent[1]);

// Waiting thread
  AfxBeginThread(LpThreadMaster,(LPVOID)hEvent);

LpThreadWorker : -

UINT LpThreadWorker (LPVOID lParam)
{
 AfxMessageBox("From Thread");
 HANDLE hHandle = static_cast<HANDLE>(lParam);
 SetEvent(hHandle);

return 0;
}

LpThreadMaster : -

UINT LpThreadMaster (LPVOID lParam)
{
  HANDLE* hHandle = static_cast<HANDLE*>(lParam);
  WaitForMultipleObjects(2,hHandle,true,INFINITE);

AfxMessageBox("From Thread complete");
  CloseHandle(hHandle[0]);
  CloseHandle(hHandle[1]);
  return 0;
}

Executing above code:
1. When main thread starts, all worker thread get started, two threads are blocked by MessageBox and one thread is waiting for event to occur from different thread.

2. whenever  user click on Ok button of  MessageBox, the event is set and once all event for whom WaitForMultipleObject is waiting are set, it will succeed and another message box is displayed showing success.

Closing the application gracefully from other application?

There are numerous method to close the application from different application, some of them I have listed here!.

• Send WM_SYSCOMMAND specifying the SC_CLOSE as parameter, this work same way as ALT+F4 works. I have used the FindWindow api to find window HWND of target window. In example it is Notepad app ( to know more about FindWindow, click here )
  

  CWnd *NtWnd = FindWindow(L"Notepad",NULL);
NtWnd->PostMessage(WM_SYSCOMMAND,SC_CLOSE,0);


• Use SendInput api to send to simulate the ALT+F4.

//send the ALT key message

INPUT inputStuctAlt,inputStuctF4;
inputStuctAlt.type = INPUT_KEYBOARD;
inputStuctAlt.ki.dwFlags = KEYEVENTF_EXTENDEDKEY;
inputStuctAlt.ki.dwExtraInfo = 0;
inputStuctAlt.ki.wScan = 0x12;//
inputStuctAlt.ki.wVk=VK_MENU;
inputStuctAlt.ki.time = GetTickCount();

SendInput(1,&inputStuctAlt,sizeof(inputStuctAlt));

//send the F4 down key message
inputStuctF4.type = INPUT_KEYBOARD;
inputStuctF4.ki.dwFlags = KEYEVENTF_EXTENDEDKEY;
inputStuctF4.ki.dwExtraInfo = 0;
inputStuctF4.ki.wScan =VK_F4;//
inputStuctF4.ki.wVk=VK_MENU;
inputStuctF4.ki.time = GetTickCount();
SendInput(1,&inputStuctF4,sizeof(inputStuctF4));

//send the F4 up key message
inputStuctF4.ki.dwFlags = KEYEVENTF_EXTENDEDKEY|KEYEVENTF_KEYUP;
inputStuctF4.ki.time = GetTickCount();
SendInput(1,&inputStuctF4,sizeof(inputStuctF4));

//send the ALT up key message
inputStuctAlt.ki.dwFlags = KEYEVENTF_EXTENDEDKEY|KEYEVENTF_KEYUP;
inputStuctAlt.ki.time = GetTickCount();
SendInput(1,&inputStuctF4,sizeof(inputStuctF4));

Closing the application gracefully from other application?

There are numerous method to close the application from different application, some of them I have listed here!.

• Send WM_SYSCOMMAND specifying the SC_CLOSE as parameter, this work same way as ALT+F4 works. I have used the FindWindow api to find window HWND of target window. In example it is Notepad app ( to know more about FindWindow, click here )
  

  CWnd *NtWnd = FindWindow(L"Notepad",NULL);
NtWnd->PostMessage(WM_SYSCOMMAND,SC_CLOSE,0);


• Use SendInput api to send to simulate the ALT+F4.

//send the ALT key message

INPUT inputStuctAlt,inputStuctF4;
inputStuctAlt.type = INPUT_KEYBOARD;
inputStuctAlt.ki.dwFlags = KEYEVENTF_EXTENDEDKEY;
inputStuctAlt.ki.dwExtraInfo = 0;
inputStuctAlt.ki.wScan = 0x12;//
inputStuctAlt.ki.wVk=VK_MENU;
inputStuctAlt.ki.time = GetTickCount();

SendInput(1,&inputStuctAlt,sizeof(inputStuctAlt));

//send the F4 down key message
inputStuctF4.type = INPUT_KEYBOARD;
inputStuctF4.ki.dwFlags = KEYEVENTF_EXTENDEDKEY;
inputStuctF4.ki.dwExtraInfo = 0;
inputStuctF4.ki.wScan =VK_F4;//
inputStuctF4.ki.wVk=VK_MENU;
inputStuctF4.ki.time = GetTickCount();
SendInput(1,&inputStuctF4,sizeof(inputStuctF4));

//send the F4 up key message
inputStuctF4.ki.dwFlags = KEYEVENTF_EXTENDEDKEY|KEYEVENTF_KEYUP;
inputStuctF4.ki.time = GetTickCount();
SendInput(1,&inputStuctF4,sizeof(inputStuctF4));

//send the ALT up key message
inputStuctAlt.ki.dwFlags = KEYEVENTF_EXTENDEDKEY|KEYEVENTF_KEYUP;
inputStuctAlt.ki.time = GetTickCount();
SendInput(1,&inputStuctF4,sizeof(inputStuctF4));