CallMsgFilter function

Passes the specified message and hook code to the hook procedures associated with the WH_SYSMSGFILTER and WH_MSGFILTER hooks. A WH_SYSMSGFILTER or WH_MSGFILTER hook procedure is an application-defined callback function that examines and, optionally, modifies messages for a dialog box, message box, menu, or scroll bar.

Syntax

BOOL WINAPI CallMsgFilter(
  _In_ LPMSG lpMsg,
  _In_ int   nCode
);

Parameters

lpMsg [in]

Type: LPMSG

A pointer to an MSG structure that contains the message to be passed to the hook procedures.

nCode [in]

Type: int

An application-defined code used by the hook procedure to determine how to process the message. The code must not have the same value as system-defined hook codes (MSGF_ and HC_) associated with the WH_SYSMSGFILTER and WH_MSGFILTER hooks.

Return value

Type:

Type: BOOL

If the application should process the message further, the return value is zero.

If the application should not process the message further, the return value is nonzero.

Remarks

The system calls CallMsgFilter to enable applications to examine and control the flow of messages during internal processing of dialog boxes, message boxes, menus, and scroll bars, or when the user activates a different window by pressing the ALT+TAB key combination.

Install this hook procedure by using the SetWindowsHookEx function.

Examples

For an example, see WH_MSGFILTER and WH_SYSMSGFILTER Hooks.

Requirements

See also

Reference

MessageProc

MSG

SetWindowsHookEx

SysMsgProc

Conceptual

Hooks