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Intercepting WM_KEYDOWN messages

Posted on 1998-08-12
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Last Modified: 2013-11-20
How do I intercept all WM_KEYDOWN messages regardless of which window they routed to ?
Basically I am trying to write an app which will run in the background and monitor all keystrokes and pop up a dialog when it receives a particular keystroke combination.
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Question by:davidmurphy
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5 Comments
 
LVL 1

Expert Comment

by:amby
ID: 1320637
You can change the window proc of each window you want to "trace", the instruction is SetWindowLong...

CMyWnd::OnWhatYouWant()
{
    //----- do it in every window you want to trace...
    OldWndProc = SetWindowLong(m_hWnd, GWL_WNDPROC, NewWndProc)
}

UINT NewWndProc (HWND, MESSAGE, LPARAM, WPARAM)
{
    //---- HWND identifies the window !!!

    //---- refer to online doc for exact syntax
    switch (MESSAGE) {
    case WM_KEYDOWN:
        ExecMyCode();
        break;
    }

    //---- It is often interesting...
    return CallWindowProc(OldWndProc,...);
}

Good luck
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Author Comment

by:davidmurphy
ID: 1320638
Thank you for your answer but I dont think that it is quite what I am looking for.
Isn't there a way of hooking into the windows message queue in the same way (I imagine) that 'Spy' works ?

Thanks
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LVL 1

Expert Comment

by:amby
ID: 1320639
I imagine Spy is modifying the window proc...

(in fac you can "empile" the window procs, very usefull !!)
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LVL 3

Expert Comment

by:danny_pav
ID: 1320640
You want to look at HOOKs.
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LVL 1

Accepted Solution

by:
arun_ta earned 200 total points
ID: 1320641
u might like to use Windows Message Hooks (Spy does that...) - except for a DOS window. Enough documentation is there in help files.

Another advanced method is to write a simple driver which intercepts the calls to windows kbd driver. (Visit sysinternals.com for an example)


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