The GetMessageExtraInfo function gets the extra message information for the current thread. Extra message information is an application- or driver-defined 32-bit value associated with the current thread's message queue. You can use the SetMessageExtraInfo function to set a thread's extra message information, which will remain until the next call to GetMessage or PeekMessage.
LONG GetMessageExtraInfo(VOID)
This function has no parameters.
The return value specifies the extra information. The meaning of the extra information is device specific.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in winuser.h.
Import Library: Use user32.lib.
Messages and Message Queues Overview, Message and Message Queue Functions, GetMessage, PeekMessage, SetMessageExtraInfo