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SetWindowsHookEx The SetWindowsHookEx function installs an application-defined hook procedure into a hook chain. You would install a hook procedure to monitor the system for certain types of events. These events are associated either with a specific thread or with all threads in the system.
VB4-32,5,6
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 |
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Operating Systems Supported |
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Requires Windows NT 3.1 or later; Requires Windows 95 or later |
- 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. |
If the function succeeds, the return value is the handle of the hook procedure.
If the function fails, the return value is NULL. |
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