PRB: Child CPropertySheet Hangs if Focus is Switched

ID: Q149501


The information in this article applies to:


SYMPTOMS

If a modeless CPropertySheet is a child of a CDialog or another CPropertySheet, the program will hang in the following situations:

The program hangs because the child CPropertySheet continuously receives a WM_GETDLGCODE message.


CAUSE

By default, CPropertyPages have a WS_EX_CONTROLPARENT style. However, CPropertySheets do not have this style. This style allows a user to press the TAB key to move from a control inside the page to one in the sheet.

When the focus is switched from the CPropertyPage, code that handles default command buttons loops through all the controls in the pages and the sheet. Cycling through controls is done using GetNextDlgTabItem(). The loop cycles through controls in the page in the child CPropertySheet and finds its way to controls in the parent page or parent dialog. At this point, GetNextDlgTabItem() is not able to find controls inside the child CPropertySheet because it doesn't have a WS_EX_CONTROLPARENT style. The loop never ends because it never finds the original control that had the focus.


RESOLUTION

Override OnInitDialog() for the child CPropertySheet, and add the WS_EX_CONTROLPARENT style.


STATUS

This is a problem with the implementation of the Property Sheet common control, and not MFC's CPropertySheet wrapper. The problem has been fixed in Windows NT 4.0.


MORE INFORMATION

Sample Code


   // CMySheet is derived from CPropertySheet
   BOOL CMySheet::OnInitDialog()
   {
             ModifyStyleEx (0, WS_EX_CONTROLPARENT);
             return CPropertySheet::OnInitDialog();
   }

   /* Compile options needed: default
   */  

Additional query words: WS_CHILD Property Sheet lock freeze page modal


Keywords          : kbprg kbMFC KbUIDesign kbVC 
Version           : WINDOWS:1.0; winnt:4.0a
Platform          : WINDOWS winnt 
Issue type        : kbprb 

Last Reviewed: June 22, 1999