endless messages WM_GETDLGCODE when focus is lost
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Thread: endless messages WM_GETDLGCODE when focus is lost

  1. #1
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    endless messages WM_GETDLGCODE when focus is lost

    I have an ActiveX component (it contains several child windows). I put the component into usual modal dialog (MFC 4.2). The following problem appears: when input focus is located in one of fields of the ActiveX, I press Alt-Tab to go to another application. Since this moment my programs hangs over because of endless messages WM_GETDLGCODE. They come to the child window of the ActiveX where the focus was located before leave.

    How may I fix the problem?

  2. #2
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    Angry Re: endless messages WM_GETDLGCODE when focus is lost

    I have the same issue!

    Has someone any idea what can be the problem? Please.

    My Window structure is:

    MainAppWindow
    MDIClient
    Dialog
    ActiveX (VB6) as container
    SSTab (VB6)
    .NET Interop UserControl as ActiveX

    When I click on button in Dialog window new dialog is opened. When I close it, and click on one of the inner controls (i.e. TextBox) in the .NET Interop UserControl it will jump into infinity loop raising WM_GETDLGCODE message (as seen in Spy++). The message problem is in ActiveX (VB6).


    Thanks.

    Michal
    Last edited by vlko; July 4th, 2007 at 05:11 AM.

  3. #3
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
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    Re: endless messages WM_GETDLGCODE when focus is lost

    Not sure there might be your case(s):
    KB179696
    KB177103
    Victor Nijegorodov

  4. #4
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    Re: endless messages WM_GETDLGCODE when focus is lost

    Thank you for fast answear Viktor.

    That KB articles looks similar but I have problem with Click event. I'm not pressing any key when I'm trying to focus inner TextBox control.

    What I already tested is, that when I will close that dialog and click firstly on SSTab (so I will focus it) and after I will click into .NET Control (into it's textbox) everyting works and no WM_GETDLGCODE is generated.

    I'm resolving it for 2 weeks already, and I'm realy out of ideas how to fix it.

    Is there a way to correctly return from WM_GETDLGCODE message? I was trying to override wndproc of that VB6 ActiveX and handle that WM_GETDLGCODE message. But whatever I returned, it was always endless loop.

    Michal

  5. #5
    VictorN's Avatar
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    Re: endless messages WM_GETDLGCODE when focus is lost

    Sorry, I have no idea because I never worked (so tightly) with ActiveX.
    Try to search in Google Groups for such a problem
    Victor Nijegorodov

  6. #6
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    Re: endless messages WM_GETDLGCODE when focus is lost

    Here's how I override WM_GETDLGCODE (in Win32):

    Code:
    	case WM_GETDLGCODE: {
    		LRESULT result = CallWindowProc(oldproc, hWnd, msg, wParam, lParam);
    
    		MSG *m = (LPMSG) lParam;
    		if(m) {
    			if(m->wParam == VK_ESCAPE) return result | DLGC_WANTALLKEYS;
    			else if(m->wParam == VK_RETURN) return result | DLGC_WANTALLKEYS;
    		}
    		return result;
    	}
    If I remember correctly, this was used in a subclass of an edit control where I wanted to override the default behavior of enter and escape.

    I've seen endless or infinite WM_GETDLGCODE before...I checked some old code I have of a custom control (not active x) where I had to mess with tab order to prevent it. Here it is...not sure if it will apply in your case. This is code from a WM_CREATE handler for a custom grid control. I'm creating a dummy control to workaround the infinite loop problem.:

    Code:
    case WM_CREATE:
    ...
    
    	// Create a non-visible 'ENDGROUP' static control, and put tabposition of main grid ctl after it
    	// This is to fix problem of infinite loop of WM_GETDLGCODE messages with WS_GROUP & WS_EX_CONTROLPARENT & radio buttons.
    	// Problem was that adding radio buttons would cause a hang - something to do with the dialog-keyboard logic.
    	// This solution puts a non-WS_EX_CONTROLPARENT control ('ENDGROUP') before the main grid ctl window with a WS_GROUP style.
    	// This seems to cause the dialog-keyboard logic to stop before the WS_EX_CONTROLPARENT control.
    	// NOTE: there is a little wierdness because a child window (ENDGROUP) has a tab position before its parent
    	//		 (the main grid ctl window) Hopefully this isnt a problem. If it is, then ENDGROUP would have to be a sibling
    	//	     of gridctl and gridctls WM_DESTROY handler would have to destroy ENDGROUP
    	HWND h = CreateWindowEx(0, "STATIC", "ENDGROUP", WS_CHILD | WS_GROUP, 0, 0, 0, 0, hWnd, (HMENU) NULL, lpcs->hInstance, (LPVOID) NULL);
    	SetWindowPos(hMyCustomControlWnd, h, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
    Last edited by Martin O; July 4th, 2007 at 09:58 AM.

  7. #7
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    Re: endless messages WM_GETDLGCODE when focus is lost

    First of all, that you for your post it. I will try new things.
    My issue here is that I cannot handle WM_CREATE message in ActiveX, because I can hook to wndproc only after Initialize method is called on the OCX. And it is VB6 stuff .

    Michal

  8. #8
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    Re: endless messages WM_GETDLGCODE when focus is lost

    Good news I solved it

    The issue was, that ActiveX didn't had EXSTYLE WS_EX_CONTROLPARENT. I don't know background about this style but after adding this style through SetWindowLong() .NET Control gets focus and doesn't freeze anymore.

    That style stoped WM_GETDLGCODE flooding.

    For me it's a mistery solution, but works!

    Thank you to all people that wanted to help me.

    Michal

  9. #9
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    Re: endless messages WM_GETDLGCODE when focus is lost

    Ok I found one site that showed me a little light for this topic:

    http://blogs.msdn.com/oldnewthing/ar...30/201988.aspx

  10. #10
    VictorN's Avatar
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    Re: endless messages WM_GETDLGCODE when focus is lost

    Quote Originally Posted by vlko
    Good news I solved it

    The issue was, that ActiveX didn't had EXSTYLE WS_EX_CONTROLPARENT.
    Oh, YES!
    Now I remember, I hadthe similar situation about 7 years ago but with a child control on the modeless property page:
    PRB: Child CPropertySheet Hangs If Focus Is Switched
    Victor Nijegorodov

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