消息队列-WinAPI

Question

the message queue is present in any type of program or Unix is present only in programs written in Windows interface?

For example this programm:

int main()
{
    short int n;
    while(1)
    {
        if (n = GetKeyState(VK_UP))
        {   
            cout << n;
        }
        else
        {
            cout << n;
        }

    Sleep(150);
    }

    return 0;
}

have or not the message queue? If yes, the GetKeyState function retrieves the keyboard messages from the message queue?

Answer 1

Yes, you must call PeekMessage or GetMessage to make GetKeyState return new values, for further reading look here:

http://blogs.msdn.com/b/oldnewthing/archive/2004/11/30/272262.aspx

and here:

http://msdn.microsoft.com/en-us/library/windows/desktop/ms646301%28v=vs.85%29.aspx

If you dont want message loop use GetAsyncKeyState .

Answer 2

GetKeyState is a Windows function that interacts closely with the Windows message queue. The function does not exist in Unix.

As I explained in your previous question, GetKeyState provides information about the key state associated with the most recently retrieved message. Since your console application does not have a message queue, and is not pumping messages, GetKeyState yields no useful information.

Again, as explained in your previous question, you use GetAsyncKeyState to obtain information about the state at the instant that the API call is made .

Finally, again repeating statements from your earlier question, test for a key being pressed by checking for a negative return value. For instance:

if (GetAsyncKeyState(VK_UP) < 0)
    ....

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