This article was previously published under Q151032
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A splitter window is a special window with the capability of being split into multiple panes, each usually containing a view. Although the Online documentation says that any CWnd object can replace a view in a pane, it does not elaborate on how to do so.
GENSPLIT shows how to put different types of windows in splitter panes. The sample creates an SDI application and creates a splitter window with four panes. The panes contain a view, a generic CWnd derived window, a listbox, and a dialog.
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GENSPLIT is an MFC SDI application in which CMainFrame::OnCreateClient has been overridden to create a static splitter with two rows and two columns. For more information on splitter windows and how to create them, please see Online Help or the REFERENCES section in this article.
To create windows in the splitter panes, MFC uses CRuntime class information. This information is passed to the CSplitterWnd::CreateView call using the RUNTIME_CLASS macro. This API creates the panes in the splitter. It first calls CreateObject to create the MFC object and then calls the virtual function CWnd::Create to create the window. Any MFC class willing to implement creation using runtime class information must be tagged DECLARE_DYNCREATE. The corresponding macro, IMPLEMENT_DYNCREATE, must be added to the implementation file for the class. Also, CWnd::PostNcDestroy needs to be overridden for the class and it should make a call to delete this pointer. This brings about cleanup of the dynamically created MFC object.
In the GENSPLIT sample, the first pane is a simple view. This view is the one associated with the document template registered in the application's InitInstance.
The second pane is a window represented by an MFC class that is derived directly from CWnd. The window shows a bouncing ball. To create this pane, CreateView was passed the Runtime class information for the class.
The third pane is a listbox. Besides using the call to CreateView, there is an extra step necessary here. As mentioned above, the pane window is created by making the virtual call CWnd::Create. The CListBox class does not have a Create function whose parameter list matches that of the virtual function CWnd::Create. As a consequence, CreateView's call to Create gets resolved to CWnd::Create rather than to CListBox::Create.
All CListBox::Create does is set the WINDOW class to "LISTBOX" and then call CWnd::Create. Since setting the WINDOW class is the only step missing in the pane creation, CWnd::PreCreateWindow has been overridden for the Listbox class to set the lpszClass member of CREATESTRUCT to "LISTBOX". In this function, listbox-specific window styles have also been set.
The process to place new Common controls in splitter panes is similar to the one discussed above for Listbox controls. However, there is one important difference: Before setting the WINDOW class, you may need to call InitCommonControls(). This SDK API is necessary to load the Common control DLL into memory. It is this DLL that is responsible for registering the WINDOW classes for the Common controls. You need to call this API only if you haven't already loaded this DLL. This can be done indirectly by creating a Common control elsewhere in your application.
The fourth pane is a dialog. Creating a dialog in a pane is slightly tricky. All the windows created in the panes of a splitter are child windows of the splitter. Dialog windows are usually pop-up windows. They can be created as child windows but there is no way to specify the child ID for them. The splitter window architecture dictates which panes get which IDs. Also, as in the case of CListBox, CDialog::Create does not have the same argument list as CWnd::Create.
Since dialog creation does not go through CWnd::Create, PreCreateWindow never gets called for CDialog-derived classes. As a consequence, CWnd::Create was overridden in the CDialog-derived class. Here the base class call CDialog::Create was made that creates the modeless dialog. Immediately after this ::SetWindowLong was called to set the child ID of the dialog to whatever the splitter window architecture demands.
NOTE: The easiest way to provide dialog-like functionality in a pane is to work with the CFormView class.