Microsoft KB Archive/228448

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PRB: TAPI Callback Function Not Called When Using a Hidden Window for Notification

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Q228448

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The information in this article applies to:


 * Microsoft Win32 Application Programming Interface (API), included with:
 * Microsoft Windows NT Server version 4.0
 * Microsoft Windows NT Workstation version 4.0
 * Microsoft Windows 98
 * Microsoft Windows 95
 * the operating system: Microsoft Windows 2000

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SYMPTOMS
The TAPI callback function does not get called if you use the hidden window method of event notification in a TAPI application by calling lineInitializeEx with the dwOptions field in the LINEINITIALIZEEXPARAMS structure set to LINEINITIALIZEEXOPTION_USEHIDDENWINDOW, or by calling lineInitialize.

CAUSE
When the hidden window method of notification is used in a TAPI application, TAPI creates a hidden window for the application in the context of the thread that called lineInitializeEx. If the thread that calls lineInitializeEx does not retrieve and dispatch windows messages, the hidden window does not receive Windows messages, and in turn, the callback function registered by the TAPI application is not called.

NOTE: Calling lineInitialize is equivalent to calling lineInitializeEx with the LINEINITIALIZEEXOPTION_USEHIDDENWINDOW option, so using lineInitialize instead of lineInitializeEx results in the same behavior.

RESOLUTION
Make sure the thread that calls lineInitializeEx or lineInitialize contains a message loop that retrieves and dispatches messages for the hidden window.

STATUS
This behavior is by design.

Additional query words:

Keywords : kbAPI kbKernBase kbOSWinNT400 kbOSWin2000 kbTAPI kbOSWin95 kbOSWin98 kbDSupport kbGrpDSKernBase

Issue type : kbprb

Technology : kbAudDeveloper kbWin32sSearch kbWin32API