Setting SystemJournal Hooks with VB

[ShepherdOfChaos]

Can anybody point me to an example of how to do this with Visual Basic code?

The best API book I have is Dan Appleman's Guide for VB5.0, and he doesn't even touch the subject of system hooks. There are some really powerful programming techniques to be mined here if some guru would be kind enough to throw up some example code in VB.

[ShepherdOfChaos]

Found some interesting material:


---------------------------------------------------------------------
The information in this article applies to:
- Microsoft Visual Basic Learning, Professional, and Enterprise Editions
for Windows, version 5.0
---------------------------------------------------------------------SUMMARY
=======This article demonstrates how to intercept input from the keyboard before
it reaches your Visual Basic application. Most keyboard input can be
readily intercepted by a Visual Basic application by using the KeyDown
event of the form or control. The technique shown here allows you how to
handle otherwise unavailable key combinations such as the TAB key or access
key combinations.MORE INFORMATION================
You can create a keyboard hook that intercepts all keyboard input directed
to a given thread. To create this hook, you must replace the default
KeyboardProc() function with a KeyboardProc() of your own. The AddressOf()
construct introduced in Visual Basic 5.0 makes this possible. Within your
KeyboardProc(), you must either pass along the keyboard input you receive
or delete it. You cannot change the contents of the message you receive.
Why would you want to do this? One purpose of the keyboard hook could be to
enforce data validation before the current control loses focus. Another
purpose is to work around the difference in event sequence when using an
access (or hot key) as opposed to a TAB character or mouse click.
For additional information on this problem, please see the following
article in the Microsoft Knowledge Base: ARTICLE-ID: Q74905
TITLE : PRB: Access Key Causes Different Event Order than Mouse
Click
The next section illustrates how to create a sample application that works
around this behavior by intercepting the access key, setting the focus, and
then causing a mouse-click event to occur. Please note that this does not
resolve all issues with the key order problems. For example, calling
Message boxes from an event affects the event order as well.
WARNING: Failure to unhook the keyboard hook before exiting your
application will result in errors, Invalid Page Faults, and data loss. This
is caused by the system pointing to the your KeyboardProc() function, which
no longer exists because it has not been notified of the change. Always
unhook the keyboard upon exiting the application. This is especially
important while debugging a program that uses this technique within the
Microsoft Visual Basic 5.0 Development Environment. Clicking the End button
or selecting End from the Run menu without unhooking will cause an Invalid
Page Fault and close Microsoft Visual Basic without giving you a chance to
save your code.Steps to Create Sample Project-----------------------------
1. Start a new Standard EXE project in Visual Basic. Form1 is created by
default.
2. Add a TextBox and a CommandButton to Form1. Set the TabIndex of the
TextBox to 0.
3. Add a module to the project. From the Project menu, click Add Module.
4. Copy the following code to the Code window of Module1:
Public Declare Function CallNextHookEx Lib "user32" _
(ByVal hHook As Long, _ ByVal nCode As Long, _
ByVal wParam As Long, _ ByVal lParam As Long) As Long
Public Declare Function UnhookWindowsHookEx Lib "user32" _
(ByVal hHook As Long) As Long
Public 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
Public Declare Function PostMessage Lib "user32" _
Alias "PostMessageA" _ (ByVal hwnd As Long, _
ByVal wMsg As Long, _ ByVal wParam As Long, _
ByVal lParam As Long) As Long Public Const WH_KEYBOARD = 2
Public Const KBH_MASK = &H20000000
Public Const WM_LBUTTONDOWN = &H201 Public Const WM_LBUTTONUP = &H202
Global hHook As Long
Public Function KeyboardProc(ByVal nCode As Long, _
ByVal wParam As Long, _
ByVal lParam As Long) As Long
If nCode >= 0 Then 'Process keys you want to filter
If wParam = Asc("C") And (lParam And KBH_MASK) <> 0 Then
If (lParam And &HC0000000) = 0 Then
Form1.Command1.SetFocus
Call PostMessage(Form1.Command1.hwnd, _
WM_LBUTTONDOWN, _
0, _
&H20002)
Call PostMessage(Form1.Command1.hwnd, _
WM_LBUTTONUP, _
0, _
&H20002)
KeyboardProc = 1 Exit Function
End If End If End If
KeyboardProc = CallNextHookEx(hHook, nCode, wParam, lParam)
End Function
5. Copy the following code to the Code window of the Form1 form:
Option Explicit Private Sub Command1_Click()
Debug.Print "Command1_Click" End Sub
Private Sub Command1_GotFocus() Debug.Print "Command1_GotFocus"
End Sub Private Sub Form_Load()
hHook = SetWindowsHookEx(WH_KEYBOARD, _
AddressOf KeyboardProc, _
0&, _
App.ThreadID) End Sub
Private Sub Form_Unload(Cancel As Integer)
Call UnhookWindowsHookEx(hHook) End Sub
Private Sub Text1_LostFocus() Debug.Print "Text1_LostFocus"
End Sub4. Press the F5 key to run the program.
The text box should have the focus. Click the CommandButton and note
the sequence of events that occur as show in the debug window:
Text1_LostFocus Command1_GotFocus Command1_Click
Set the focus to the text box and press the ALT+C keys and note that the
same events occur.Notes-----
Hooks do not always behave the same way in the IDE as they do in an EXE.
Make certain that you test your solution in an EXE before you move on to
other parts of your project.
It is possible to intercept all of the keyboard input on a system, but not
using "pure" Visual Basic. The hook must be placed in a standard DLL; while
Visual Basic 5.0 can create OLE DLLs, it cannot create standard DLLs.
(c) Microsoft Corporation 1997, All Rights Reserved.
Contributions by Arsenio Locsin, Microsoft Corporation
======================================================================
Keywords : vb5all vb5howto VBKBWinAPIVersion : WINDOWS:5.0
Platform : WINDOWSIssue type : kbhowto

This looks very interesting, but I think it only applies to local hooks within a single process. What I want to do is set a system wide journal hook so that I can tell whether another application has caused any keyboard or mouse events.

I have a C Windows Development book that says that in general it is true that you have to place remote hooks (meaning hooks that intercept messages intended for other processes) in a standard DLL (meaning you have to write your own in C++). However, it also says that system wide journal hooks are an exception; that they must occupy the same process address space as the process that set them. So it should be possible to do this with VB 5.0.

If anyone knows of an example in VB, please post it (or a link) here. In the meantime, I'll keep looking.

[Edited by ShepherdOfChaos on 03-29-2000 at 10:30 PM]