Why are “TranslateMessage” and “DispatchMessage” separate calls?

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The more traditional message loop looks like this:

while (GetMessage(&msg, 0, 0, 0)) 
{
    if (!TranslateAccelerator(hwndMain, haccel, &msg))
    {
        TranslateMessage(&msg); 
        DispatchMessage(&msg); 
    } 
}

It is a pretty big hint to what you’d want to do before dispatching the message: catch messages that ought to be intercepted and treated specially before the window sees them. Keyboard shortcuts are a classic example, they need to be detected no matter what window has the focus.

Any GUI class library exposes it with a virtual method named something like App.PreProcessMessage, a virtual function that can be overridden so your program can implement its own shortcuts and whatnot.

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