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Requirements of an IViewHelper Clone-View COM Object

Last Updated: 2/14/2017

A hardware vendor's clone-view IViewHelper COM interface object must meet the following requirements:

  • The COM object must reside within a dynamic-link library (DLL), which is a COM in-process (in-proc) server.

  • The implementation of the COM object must be opaque to the operating system.

  • The IViewHelper interface must provide methods for getting and setting the topology data, which includes clone view.

  • The hardware vendor must find a display mode for clone view so that the display is shown on two or more monitors.

  • If a call to the COM object's IViewHelper::Commit method does not generate a mode change, Commit must call the Win32 BroadcastSystemMessage function and must always post (using the BSF_POSTMESSAGE broadcast option) a WM_DISPLAYCHANGE message. For more information about BroadcastSystemMessage, see the Microsoft Windows SDK documentation.

  • The IViewHelper::Commit method must not be used in place of a call to the Win32 ChangeDisplaySettingsEx(NULL, NULL, NULL, 0, NULL) function with the indicated arguments. For more information about ChangeDisplaySettingsEx, see the Windows SDK documentation.

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