HOWTO: Subclass a Dialog Item in ATL

• The Microsoft Active Template Library (ATL), versions 2.0, 2.1, 3.0, used with:
  • Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1, 4.2, 5.0, 6.0

SUMMARY

This article describes how to subclass a control on the dialog box resource template using ATL.

MORE INFORMATION

You need to perform the following steps to subclass a control, such as the ComboBox, on the dialog template in an ATL project:

1. Declare a member of type CContainedWindow in the CDialogImpl-derived class for the Dialog Template as:

   
         CContainedWindow   m_ComboBox; 




2. Initialize the CContainedWindow member in the constructor of the CDialogImpl-derived class (CMyDialog class) with the appropriate class name as:

   
         CMyDialog::CMyDialog() : m_ComboBox(_T("COMBOBOX"), this, 1) 




3. Add WM_INITDIALOG and WM_DESTROY message handlers, and an Altered Message Map (ALT_MSG_MAP), to the default Message Map of the CDialogImpl-derived class. The Altered Message Map is used to trap messages that are sent to the subclassed control, as in the following example:

   Sample Code

   
   BEGIN_MSG_MAP(CMyDialog)
      MESSAGE_HANDLER(WM_INITDIALOG, OnInitDialog)
      MESSAGE_HANDLER(WM_DESTROY, OnDestroy)
   
   ALT_MSG_MAP(1)   // Handlers for the subclassed combo box.
      MESSAGE_HANDLER(WM_RBUTTONDOWN, OnRBtnDown) // Trap a right[ASCII 150]click.
   END_MSG_MAP() 




4. In the WM_INITDIALOG handler of the CDialogImpl-derived class, subclass the ComboBox as:

   
         m_ComboBox.SubclassWindow(::GetDlgItem(m_hWnd,IDC_SUB_COMBOBOX)); 




5. In the WM_DESTROY handler of the CDialogImpl derived class unsubclass the ComboBox as:

   
         m_ComboBox.UnsubclassWindow(); 

Additional query words: ocx kbATL200 kbATL210 kbATL300 kbvc400 kbvc410 kbvc420 kbvc500 kbvc600 kbserver kbctrl

Keywords : kbATL200 kbATL210 kbCtrl kbDlg kbVC420 kbVC500 kbVC600 kbATL300 kbGrpMFCATL kbArchitecture
Version : WINDOWS:2.0,2.1,3.0
Platform : WINDOWS
Issue type : kbhowto