Microsoft KB Archive/152542

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DOCERR: WM_DEVICECHANGE Message Replaces WM_STARTSESSION

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Q152542

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The information in this article applies to:


 * Microsoft Win32 Device Driver Kit (DDK) Windows 95

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SUMMARY
The Windows 95 documentation erroneously contains references to the WM_STARTSESSION notification message, stating that this message informs VxDs that the Windows user interface component is now active and that the SHELL_CallAtAppyTime services will now work.

The WM_STARTSESSION message does not actually exist. Instead, you can use the WM_DEVICECHANGE message as listed in the \ddk\inc32\dbt.h header file. The following is an excerpt from dbt.h:

  /* * Message = WM_DEVICECHANGE * wParam = DBT_APPYBEGIN * lParam = (not used) *   * 'Appy-time is now available. This message is itself sent * at 'Appy-time. *   * Message = WM_DEVICECHANGE * wParam = DBT_APPYEND * lParam = (not used) *   * 'Appy-time is no longer available. This message is *NOT* sent * at 'Appy-time. (It cannot be, because 'Appy-time is gone.) *   * NOTE! It is possible for DBT_APPYBEGIN and DBT_APPYEND to be sent * multiple times during a single Windows session. Each appearance of   * 'Appy-time is bracketed by these two messages, but 'Appy-time may * momentarily become unavailable during otherwise normal Windows * processing. The current status of 'Appy-time availability can always * be obtained from a call to _SHELL_QueryAppyTimeAvailable. */