sending keyboard msgs to childwindows

This is a discussion on sending keyboard msgs to childwindows within the Windows Programming forums, part of the Platform Specific Boards category; hey, I have a custom control and would like it to recieve a WM_KEYDOWN msg, more in particular, the backspace ...

  1. #1
    btq
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    julie lexx... btq's Avatar
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    sending keyboard msgs to childwindows

    hey,
    I have a custom control and would like it to recieve a WM_KEYDOWN msg,
    more in particular, the backspace and delete
    buttons. Is there a way to send this(WM_KEYDOWN) message
    thru the custom proc every time a key is pressed...?
    Without doing anything the control doesn't get a WM_KEYDOWN
    msg at all..
    did a search on the board, MSDN and of course on the
    trustworthy gooogle. No doubt I saw that subclassing was some
    kindofan answer, but still it doesn't seem to accomplish this?
    The whole control is a class and the GWL_USERDATA is set to point to the instance of the class..

    any help/hints/information is greatly apriciated
    thanks a bunch
    /btq
    ...viewlexx - julie lexx

  2. #2
    Guest Sebastiani's Avatar
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    Well, the simplest way is to add this to your message loop:

    Code:
    
    while( GetMessage(&msg, NULL, 0, 0) > 0)   {
       
       DispatchMessage(&msg);
    
       TranslateMessage(&msg);
    
       if(msg.message == WM_KEYDOWN) {
        SendMessage(hChild, msg.message, msg.wParam, msg.lParam);
        }
    //...
      }
    But this is not a good long term solution, and so for that I would suggest using the "controller" paradigm often pushed in the C++ community. This is a lengthy issue and so I won't go into much detail, but there are many good books on the theory, ("C++ in Action" by Bartosz Milewski comes to mind...). Suffice it to say it is a real solution to the entire problem of reliably controlling Windows.



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  3. #3
    btq
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    julie lexx... btq's Avatar
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    urghh..
    so either I have to make crapy error-prone code by sending the
    message from another messageprocedure or dig deep into my into my pocket for my librarycard?
    ack...are there no easier solutions??

    thanks for the reply though
    /btq
    ...viewlexx - julie lexx

  4. #4
    erstwhile
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    Window subclassing should be able to deal with most situations you care to code for. In this regard and with respect to your original question you may want to take a closer look at WM_GETDLGCODE to see if it will offer added functionality, particularly if your control is in a dialog and you want to retain some default dialog key capability.

  5. #5
    btq
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    aight..I've looked a bit into Subclassing but it seems that's only
    for already defined windows like "button" etc.?? I mean my window already has a
    custom proc and and it seems Subclassing wouldn't make any difference then?

    anyways, I've realised my problem was SetFocus. With SetFocus
    set to my window it received keydown messages..
    However, since this control is dynamically created by the user and all of these controls should receive the same msg, that wouldn't work with SetFocus(). So my question is: can't I just filter out the WM_KILLFOCUS? if these controls never receive a
    WM_KILLFOCUS will these messages still run through the controls
    proc then? And if it works maybe more important is: is this 'bad'
    windows programming-style?

    thanks a bunch
    /btq
    ...viewlexx - julie lexx

  6. #6
    train spotter
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    >>can't I just filter out the WM_KILLFOCUS? if these controls never receive a
    WM_KILLFOCUS will these messages still run through the controls

    Only one ctrl can have 'focus'. The user can not type into more than one ctrl at a time.
    So you will have to broadcast your msg to the other windows.
    I suggest a custom message to send on to the other windows. Store the HWNDS in an dynamic array / linked list so you can loop thru them. Or assign sequential ID's and loop that way.

    #define WM_MY_APPS_MSG WM_USER+40001

    Or look at SendMessage() with a HWND_BROADCAST (will not be sent to child wnds though)
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  7. #7
    Guest Sebastiani's Avatar
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    Going off of novacain's suggestion, how about this: In the WinMain message loop, use the SendMessage() example I gave to send all keyboard messages to the main window's proc (instead of to the child). Within the proc itself, you have in the WM_CREATE a vector/linked list/array constantly pushing new HWND's into a stack. In the WM_KEYDOWN handler, simply iterate through the stack and SendMessage(). The plus is that it is a long-term/generic solution to handling keyboard input. The minus is that no matter what, every window gets the message.

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