Function name: SetWindowsHookEx

Defined in : User32

Requirements : Windows NT 3.1 or later; Windows 95 or later

Declaration:

Declare Function SetWindowsHookEx Lib "user32" Alias "SetWindowsHookExA" (ByVal idHook As Long, ByVal lpfn As Long, ByVal hmod As Long, ByVal dwThreadId As Long) As Long

Parameters:

* idHook Specifies the type of hook procedure to be installed. This parameter can be one of the following values: WH_CALLWNDPROC Installs a hook procedure that monitors messages before the system sends them to the destination window procedure. For more information, see the CallWndProc hook procedure. WH_CALLWNDPROCRET Installs a hook procedure that monitors messages after they have been processed by the destination window procedure. For more information, see the CallWndRetProc hook procedure. WH_CBT Installs a hook procedure that receives notifications useful to a computer-based training (CBT) application. For more information, see the CBTProc hook procedure. WH_DEBUG Installs a hook procedure useful for debugging other hook procedures. For more information, see the DebugProc hook procedure. WH_GETMESSAGE Installs a hook procedure that monitors messages posted to a message queue. For more information, see the GetMsgProc hook procedure. WH_JOURNALPLAYBACK Installs a hook procedure that posts messages previously recorded by a WH_JOURNALRECORD hook procedure. For more information, see the JournalPlaybackProc hook procedure. WH_JOURNALRECORD Installs a hook procedure that records input messages posted to the system message queue. This hook is useful for recording macros. For more information, see the JournalRecordProc hook procedure. WH_KEYBOARD Installs a hook procedure that monitors keystroke messages. For more information, see the KeyboardProc hook procedure. WH_MOUSE Installs a hook procedure that monitors mouse messages. For more information, see the MouseProc hook procedure. WH_MSGFILTER Installs a hook procedure that monitors messages generated as a result of an input event in a dialog box, message box, menu, or scroll bar. For more information, see the MessageProc hook procedure. WH_SHELL Installs a hook procedure that receives notifications useful to shell applications. For more information, see the ShellProc hook procedure. WH_SYSMSGFILTER Installs a hook procedure that monitors messages generated as a result of an input event in a dialog box, message box, menu, or scroll bar. The hook procedure monitors these messages for all applications in the system. For more information, see the SysMsgProc hook procedure. * lpfn Points to the hook procedure. If the dwThreadId parameter is zero or specifies the identifier of a thread created by a different process, the lpfn parameter must point to a hook procedure in a dynamic-link library (DLL). Otherwise, lpfn can point to a hook procedure in the code associated with the current process. * hMod Identifies the DLL containing the hook procedure pointed to by the lpfn parameter. The hMod parameter must be set to NULL if the dwThreadId parameter specifies a thread created by the current process and if the hook procedure is within the code associated with the current process. * dwThreadId Specifies the identifier of the thread with which the hook procedure is to be associated. If this parameter is zero, the hook procedure is associated with all existing threads.

Returns:

If the function succeeds, the return value is the handle of the hook procedure. If the function fails, the return value is NULL.

Related functions:

Examples:

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