Windows Message-Processing Caveats

 Last reviewed: July 22, 1997
Article ID: Q64329
3.00 3.10 WINDOWS kbprg

The information in this article applies to:

  • Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0 and 3.1

Do not call any function that may cause control to yield to another application during the processing of any of the following messages: 

   WM_ACTIVATE
   WM_ACTIVATEAPP
   WM_CREATE
   WM_INITDIALOG
   WM_NCCREATE
Certain messages are used to notify applications of some change in Windows's internal status. While processing one of these messages, an application cannot call any function that may result in control being yielded to another application. Forbidden functions include message-processing functions such as MessageBox(), DialogBox(), GetMessage(), and PeekMessage().

Violating this caveat may cause Windows to exhibit strange visual behavior.

Additional reference words: 3.00 3.10
KBCategory: kbprg
KBSubcategory: UsrCtl
Keywords : kb16bitonly

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Last reviewed: July 22, 1997
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