Global (system wide) keyboard hooks - resolved

Hi, I'm developing a global high level keyboard hook, low level is of no use in this case because it doesn't trap the shift key fast enough.

Unfortunately I have a problem with the high level hook, explorer crashes everytime a key is depressed - of course this is not good. Does anyone know why this happens? And is there a possible work around for this?

Cheers.
-adehh

Show some code.

In module:

VB Code:

Option Explicit
 
Private Const WM_KEYDOWN As Long = &H100
Private Const WM_KEYUP As Long = &H101
Private Const VK_SHIFT = &H10
Private Const HC_ACTION As Integer = 0
 
Public Const WH_KEYBOARD As Long = 2
 
Private Declare Function CallNextHookEx Lib "user32" _
    (ByVal hHook As Long, _
    ByVal ncode As Long, _
    ByVal wParam As Long, _
    lParam As Any) As Long
    
Private Declare Function GetKeyState Lib "user32" _
    (ByVal nVirtKey As Long) As Integer
    
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 UnhookWindowsHookEx Lib "user32" _
    (ByVal hHook As Long) As Long
    
Public hHook As Long
 
Public Function KeyboardProc(ByVal code As Integer, ByVal wParam As Long, ByVal lParam As Long) As Long
    
    If code >= 0 Then
        Open "c:\weeeee.txt" For Append As #1
            Print #1, wParam
        Close #1
        
        KeyboardProc = CallNextHookEx(code, hHook, wParam, ByVal lParam)
    Else: KeyboardProc = CallNextHookEx(code, hHook, wParam, ByVal lParam)
    End If
End Function

In form:

VB Code:

Option Explicit
 
Private Sub Form_Load()
    hHook = SetWindowsHookEx(WH_KEYBOARD, AddressOf KeyboardProc, App.hInstance, 0&)
End Sub
 
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    UnhookWindowsHookEx hHook
End Sub

The above code works fine when I'm in the form but if I lose the focus of the form and then go back to it, it stops working.
-adehh

You can't do global hooks in VB -- they must be in a DLL (and I don't think an ActiveX dll will work, but don't quote me on that).

No, you're quite right, it is stated all over that it cannot be done in 'pure' VB. It's just the fact that it works to the point where explorer.exe always crashes out and I don't understand why.

Looks like I'm going to be learning C or whatnot, do you know if you can compile standard DLLs in C? - I'm clueless. :D
-adehh

Visual C++ for Visual Basic Developers, by Bill Locke

It tells you how to do hooks and controls and lots of good stuff. Yes, you can do a dll in C.

Heh, cheers. I've always wanted to get into C\++ but for now I think I'll just go for the low level approach as I had that working globally.
-adehh

Quote:

---

Hi, I'm developing a global high level keyboard hook, low level is of no use in this case because it doesn't trap the shift key fast enough.

---

Since the low level hook (WH_KEYBOARD_LL) gets called before the standard keyboard hook (WH_KEYBOARD) I don't know how it can not be 'fast enough'....could you explain what the problem is?

Hi, It's actually gone alright now and the low level hook works fine globally.
My previous problem was that when using GetKeyState(VK_SHIFT) to find out if the shift key is depressed and then using that value to determine if input is capitol or another alternative key etc, was sometimes not registering that the key entered was 'shifted' - so I would be left with a lowercase key whereas the thread the input was 'sent' to actually got an upercase key.
I've got round it now by using my own boolean shift variable and declaring it true or false as the shift key is pressed up/down. Maybe it was my PC being silly the other night, I'm not sure. :)
Cheers all the same!
-adehh