Using MSLU with ATL/WTL

by Michael S. Kaplan, published on 2004/11/13 17:29 -05:00, original URI: http://blogs.msdn.com/b/michkap/archive/2004/11/13/257049.aspx

If you are using the Microsoft Layer for Unicode on Windows 95/98/Me Systems in a project that uses ATL or WTL, there are some things you need to do to make it work.

• Avoid the _ATL_MIN_CRT macro -- this macro appears to be incompatible with MSLU.

• Problems with garbage text in window title bars -- It is a problem with the usage of ::DefWindowProc and ::CallWindowProc in ATL and WTL.  The way to correct this problem is to at the very start of your program add the following code:

  // Resolve UNICOWS's thunk (required) 
  ::DefWindowProc (NULL, 0, 0, 0); 

• Tim Smith explained it best:
  "The problem is that if you create an ATL window prior to ::DefWindowProc being called, then m_pfnSuperWindowProc points to the thunk [in the loader] and not the resolved address.  Then when ATL passes m_pfnSuperWindowProc into ::CallWindowProc as part of the WM_SETTEXT message, MSLU doesn't realize that it is being passed [its own] ::DefWindowProc and thus does an extra level of text conversion.  By invoking ::DefWindowProc at the start of the program, then when ATL creates a window and stores the address of ::DefWindowProc in m_pfnSuperWindowProc, it is storing the address of the MSLU routine that the MSLU ::CallWindowProc realizes does not need conversion.  In general, if you are using ATL/WTL, just add that line of code at the start of your program and be done with it.  It also should be added to any DLL that uses ATL windows [which have the same issue].

  Please note that the abvove issue has been addressed in WTL 7.0 and thus only applies to earlier versions of WTL.

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