In win32 C++ programming to close a window, should I call DestroyWindow(hWnd) myself or SendMessage(WM_CLOSE, hWnd, 0, 0)?

Question

I'm handling ESC key in my application and when this key is received I wish to close the current window.

Should I simply call DestroyWindow(hWnd) or should I SendMessage(WM_CLOSE, hWnd, 0, 0), or should I be closing the current window in some different way?

Answer 1

You should PostMessage(hWnd, WM_CLOSE, 0, 0). It puts the WM_CLOSE message into the window's message queue for processing, and the window can close properly as the message queue is cleared.

You should use PostMessage instead of SendMessage. The difference is that PostMessage simply puts the message into the message queue and returns; SendMessage waits for a response from the window, and you don't need to do that in the case of WM_CLOSE.

Answer 2

It is up to you which you use. Should the Esc key act just like clicking the close button, or should it definitely destroy the window?

The default implementation of WM_CLOSE (as found in DefWindowProc) calls DestroyWindow, so if you're not handling WM_CLOSE specifically then one is as good as another. But WM_CLOSE doesn't necessarily have to call DestroyWindow, though, so if the window in question handles it then it could do something else. For example, it could pop up a "Are you sure?"-type message box, or simply do nothing. DestroyWindow will bypass all of that.