VB6 WH_GETMESSAGE message hook - vb6

Question

hello friends，i want to monitor an IP address control's（created by CreateWindowEx） input events which is on a form.i have used the API SetWindowsHookEx to hook WH_GETMESSAGE message ,but now i cannt eat the input message as (MSG)lParam->message = WM_NULL like in C,So i need your help,friends. can you give me the solution?
here is the code:
Private Function GetMsgProc(ByVal nCode As Long, ByVal wParam As Long, ByRef lParam As Long) As Long
CopyMemory p, ByVal lParam, LenB(p)
If p.message = WM_RBUTTONDOWN And GetParent(p.hWnd) = lngHWNDCtl Then
GetMsgProc = 0
Else
GetMsgProc = CallNextHookEx(hHook, nCode, wParam, ByVal lParam)
End If
End Function
Public Sub SetHook(ByVal lngThread As Long, lngHWND As Long, bFlag As Boolean)
If bFlag Then
lngHWNDCtl = lngHWND
hHook = SetWindowsHookEx(WH_GETMESSAGE, AddressOf GetMsgProc, 0, lngThread)
Else
If hHook Then UnhookWindowsHookEx hHook
End If
End Sub

Answer 1

Skipping the call to CallNextHookEx in GetMsgProc filter function is generally a bad idea. If you do this then other filter functions in the chain will not be called. Maybe, there are none on a dev machine, but 'in the wild' there will be other applications that installed hooks. Those applications will misbehave if you prevent their filter functions from being called.
You probably wouldn't want to analyze messages that have been merely peeked from the queue, but not removed from it. GetMsgProc is called with wParam = PM_REMOVE for messages that have been removed from queue.
VB6 or C++ or whatever, it is a deadly practice to ignore MSDN specification for API. This is how GetMsgProc filter function should make a decision based on a value of its first argument:
code [in]
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.
http://msdn.microsoft.com/en-us/library/windows/desktop/ms644981%28v=vs.85%29.aspx
Although CopyMemory should work (assuming you declare it correctly), I wouldn't bother with it here. It's perfectly OK to declare 3rd parameter of filter function as ByRef lParam As MSG.
Here is the code that should be placed in a standard module (as any other code that installs hooks). It works for me if I use it to sniff WM_RBUTTONDOWN messages to, say, TextBox control placed on a main form.
Option Explicit
'http://msdn.microsoft.com/en-us/library/windows/desktop/dd162805%28v=vs.85%29.aspx
Private Type tagPOINT
x As Long
y As Long
End Type
'http://msdn.microsoft.com/en-us/library/windows/desktop/ms644958%28v=vs.85%29.aspx
Private Type MSG
hWnd As Long
message As Long
wParam As Long
lParam As Long
time As Long
pt As tagPOINT
End Type
Private bHooked As Boolean
Private hHook As Long
Private hHwndToSniff As Long
Private Const HC_Action As Long = &H0
Private Const PM_NOREMOVE As Long = &H0
Private Const PM_REMOVE As Long = &H1
Private Const WH_GETMESSAGE As Long = &H3
Private Const WM_RBUTTONDOWN As Long = &H204
'http://msdn.microsoft.com/en-us/library/windows/desktop/ms644974%28v=vs.85%29.aspx
Private Declare Function CallNextHookEx Lib "user32" _
(ByVal hHook As Long, ByVal ncode As Long, ByVal wParam As Long, lParam As Any) As Long
'http://msdn.microsoft.com/en-us/library/windows/desktop/ms644990%28v=vs.85%29.aspx
Private 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
'http://msdn.microsoft.com/en-us/library/windows/desktop/ms644993%28v=vs.85%29.aspx
Private Declare Function UnhookWindowsHookEx Lib "user32" _
(ByVal hHook As Long) As Long
Public Sub RemoveHook()
If bHooked Then
UnhookWindowsHookEx hHook
bHooked = False
End If
End Sub
Public Sub SetHook(ByVal hThreadToHook As Long, hHwndFilter As Long)
If Not bHooked Then
hHook = SetWindowsHookEx(WH_GETMESSAGE, AddressOf GetMsgProc, 0, hThreadToHook)
If hHook > 0 Then
bHooked = True
hHwndToSniff = hHwndFilter
Else
Debug.Assert False
End If
End If
End Sub
'http://msdn.microsoft.com/en-us/library/windows/desktop/ms644981%28v=vs.85%29.aspx
Private Function GetMsgProc(ByVal uCode As Long _
, ByVal wParam As Long _
, ByRef lParam As MSG) As Long
If uCode = 0 Then
If wParam = PM_REMOVE Then
If lParam.message = WM_RBUTTONDOWN Then
If lParam.hWnd = hHwndToSniff Then
MsgBox "You right-clicked a text box!"
End If
End If
End If
End If
GetMsgProc = CallNextHookEx(hHook, uCode, wParam, lParam)
End Function
The hook is installed in a form module in the following fashion:
SetHook App.ThreadID, Me.Text1.hWnd