GetMsgProc callback function
An application-defined or library-defined callback function used with the SetWindowsHookEx function. The system calls this function whenever the GetMessage or PeekMessage function has retrieved a message from an application message queue. Before returning the retrieved message to the caller, the system passes the message to the hook procedure.
The HOOKPROC type defines a pointer to this callback function. GetMsgProc is a placeholder for the application-defined or library-defined function name.
LRESULT CALLBACK GetMsgProc( _In_ int code, _In_ WPARAM wParam, _In_ LPARAM lParam );
Specifies whether the hook procedure must process the message. If code is HC_ACTION, the hook procedure must process the message. If code is less than zero, the hook procedure must pass the message to the CallNextHookEx function without further processing and should return the value returned by CallNextHookEx.
Specifies whether the message has been removed from the queue. This parameter can be one of the following values.
Value Meaning PM_NOREMOVE 0x0000
The message has not been removed from the queue. (An application called the PeekMessage function, specifying the PM_NOREMOVE flag.)
A pointer to an MSG structure that contains details about the message.
If code is less than zero, the hook procedure must return the value returned by CallNextHookEx.
If code is greater than or equal to zero, it is highly recommended that you call CallNextHookEx and return the value it returns; otherwise, other applications that have installed WH_GETMESSAGE hooks will not receive hook notifications and may behave incorrectly as a result. If the hook procedure does not call CallNextHookEx, the return value should be zero.
The GetMsgProc hook procedure can examine or modify the message. After the hook procedure returns control to the system, the GetMessage or PeekMessage function returns the message, along with any modifications, to the application that originally called it.
Minimum supported client
Windows 2000 Professional [desktop apps only]
Minimum supported server
Windows 2000 Server [desktop apps only]
|Winuser.h (include Windows.h)|