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Posted 10 Mar 2002


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Class for Synchronizing the Active State of multiple windows.

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10 Mar 20022 min read
Class for Synchronizing the Active State of multiple windows.

  • Download demo and source code - 30 Kb


    With the class ISyncActiveImpl, of this article, you can have windows that synchronize the active state with a owner window.

    Features implemented:

    • Windows that can synchronize the active state with a owner window;
    • Windows that automatically hide when the application is deactivated and when the owner window is minimized or hidden;
    • Windows that are automatically disabled when owner window is disabled.


    I will base these examples in the source-code of the demo application included in this article.

    1. Include the ISyncActiveImpl.h header file in your source-file.

    2. Derive your class from ISyncActiveImpl<>.

      class CMainDlg :
        public CDialogImpl<CMainDlg>
      , public ISyncActiveImpl<CMainDlg>
      , public CMessageFilter
    3. In your class constructor make sure that you instantiate ISyncActiveImpl<> class with the right arguments for your type of window.

      For example, for creating a dialog or frame window:

        // this dialog does not sync the active state with
        // owner and it must be always visible.
        : ISyncActiveImpl<CMainDlg>(FALSE, TRUE)

      Or for creating a floating or toolbar window:

        // this window will synchronize the active state with
        // owner and will automatically be hidden when owner
        // is hidden/minimized or when application looses the
        // active state.
        : ISyncActiveImpl<CFloatingWindow>(TRUE)
    4. In the message map of your class add a CHAIN_MSG_MAP macro.


      NOTE: Make sure that you insert it on the first entry of the message map. This is needed because the ISyncActiveImpl<> class will need to intercept some general messages (i.e. WM_CREATE).

    Under the hood

    The key for synchronizing the active state of a window lies on the WM_NCACTIVATE message. By handling or sending this message we can force the painting of a window in the active or inactive state.

    The automatically hide of a window is archived by handling the WM_ACTIVATEAPP message.

    The other two important messages that need to be handled are WM_ACTIVATE and WM_SHOWWINDOW, you can find information about them in source-code and at MSDN.

    For ending, I just want to say that when implementing this class I have run into two "strange" activation problems, read all about them in the source-code.


    • 11 mar 2002
      • first public version.

    Do you have any question or comment? Contact me!

  • License

    This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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