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Programming Code to intercept keystrokes

Posted on 2004-10-07
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Last Modified: 2008-02-26
I basically want my parent frame to intercept the keystrokes of the "q", "w", "e", "a", "s", "d", "z", "x", "c", "1", "2", "3" keys.  I tried to make an accelerator table for the Child MDI Frames, but they only respond when active to the keys I have assigned to them.  I have 2 frames that each need to, no matter what, intercept those keystrokes when the program is maximized and the parent frame has focus.

How do I do this?  Or is there a way to have the accelerator table switch frame focus on keypress...I just need it to work...and fast!

I'm designing in Visual C++ 6.0 and am using the wxWidgets libraries, currently, if that helps.

Thanks!
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Question by:vivekpara
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by:jkr
ID: 12252586
The easiest way probably is using a 'local' (i.e. non-system-wide) hook that filters for these keys and takes the appropriate action. See http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnwui/html/msdn_hooks32.asp ("Win32 Hooks")
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jkr earned 2000 total points
ID: 12252701
BTW, a little example:

HHOOK       g_hhk   =   NULL;


LRESULT CALLBACK KbdProc    (   int     nCode,  // hook code
                                WPARAM  wParam, // virtual-key code
                                LPARAM  lParam  // keystroke-message information

                            )
{

    /* VK_0 thru VK_9 are the same as ASCII '0' thru '9' (0x30 - 0x39) */
    /* VK_A thru VK_Z are the same as ASCII 'A' thru 'Z' (0x41 - 0x5A) */

    switch ( wParam)
    {

        case 'q: //...
    }

    return  (   CallNextHookEx  (   g_hhk,
                                    nCode,
                                    wParam,
                                    lParam
                                )
            );
}

void SetHook ()
{

    g_hhk   =   SetWindowsHookEx    (   WH_KEYBOARD,
                                        ( HOOKPROC) KbdProc,
                                        NULL,
                                        GetCurrentThread ()
                                    );

}
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Author Comment

by:vivekpara
ID: 12252781
Forgive my stupidity, but where would the Function go in the case Function?  Does the case statement just need brackets for each function that it would call?  Or is it more like an ENUM Table and needs to be linked?

Thanks.
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LVL 86

Expert Comment

by:jkr
ID: 12253297
>>where would the Function go in the case Function?

You'd add the functionality for handling each of the keys you're interested in in each of the 'case' branches, like

    switch ( wParam)
    {

       case 'q': //...

        HandleThatKey_q_wasPressed ();

        break;

       case 'e': //...

        HandleThatKey_e_wasPressed ();

        break;
   }

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