Detecting a Keypress outside Vb6 - vb6

Question

I am currently modifying a really old system running Windows Server 2k. One of the requirements I am working on is to block off keyboard presses at a certain window of another program which we can't modify.
Generally my process was fine as I detect keypresses and then terminate the window if they occur, However the only working code that I have found and worked with causes many issues when sometimes Control/Windows Key/etc gets stuck and the entire system tends to act out weird. This is the Code I am using for the Hook:
Public Declare Function CallNextHookEx Lib "user32" (ByVal hHook As Long, ByVal nCode As Long, ByVal wParam As Long, lParam As Any) As Long
Public Declare Function UnhookWindowsHookEx Lib "user32" (ByVal hHook As Long) As Long
Public Declare Function SetWindowsHook Lib "user32" Alias "SetWindowsHookA" (ByVal nFilterType As Long, ByVal pfnFilterProc 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 Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Global Const WH_KEYBOARD_LL = 13
Public hook As Long
Public Const HC_ACTION = 0
Type HookStruct
vkCode As Long
scancode As Long
FLAGS As Long
time As Long
dwExtraInfo As Long
End Type
Public active As Boolean
Public value As String
Public Function myfunc(ByVal code As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Dim kybd As HookStruct
myfunc = True
If code = HC_ACTION And wParam <> 257 Then
If active Then
'SendKeys "{ESC}"
'MsgBox ("keypressed")
End If
myfunc = CallNextHookEx(hook, code, wParam, lParam)
ElseIf code < 0 Then
myfunc = CallNextHookEx(hook, code, wParam, lParam)
End If
End Function
Generally the code IS working, However if you press Control, Alt or Windows key then the entire system tends to go haywire.
Is there a better method to detect those key presses outside the system/in a specific window even possibly, Or am I doing something wrong here?

Answer 1

See the following thread: Detect keypress outside your application
You can try these two other approaches to see if they are more stable:
RegisterHotKey, a function that defines a system-wide hot key:
Declare Function RegisterHotKey Lib "user32" Alias "RegisterHotKey" (ByVal hwnd As Long, ByVal id As Long, ByVal fsModifiers As Long, ByVal vk As Long) As Long
or GetAsyncKeyState, a function that determines whether a key is up or down at the time the function is called, and whether the key was pressed after a previous call to GetAsyncKeyState:
Declare Function GetAsyncKeyState Lib "user32" Alias "GetAsyncKeyState" (ByVal vKey As Long) As Integer
You could run a timer and continuously check GetAsyncKeyState to see if the key(s) you are looking for have been pressed:
Private Sub tmrKeyPressCheck_Timer()
Dim iCounter As Integer
For iCounter = 64 To 90
If CheckKey(iCounter) Then
txtKeyPressLog.Text = Hour(Now) & ":" & Minute(Now) & ":" & Second(Now) & ": " & Chr(iCounter) & vbCrLf & txtKeyPressLog.Text
End If
Next
End Sub
Private Function CheckKey(ByVal p_lngKey As Long) As Boolean
Dim iReturn As Integer
iReturn = GetAsyncKeyState(p_lngKey)
CheckKey = (iReturn <> 0)
End Function

Answer 2

This is the code that ended up working without the issues:
Private Const WH_KEYBOARD_LL = 13&
Private Const HC_ACTION = 0&
Private Const LLKHF_EXTENDED = &H1&
Private Const LLKHF_INJECTED = &H10&
Private Const LLKHF_ALTDOWN = &H20&
Private Const LLKHF_UP = &H80&
Private Const VK_RIGHT = &H27
Private Const VK_LEFT = &H25
Private Const VK_RSHIFT = &HA1
Private Type KBDLLHOOKSTRUCT
vkCode As Long
scanCode As Long
FLAGS As Long
time As Long
dwExtraInfo As Long
End Type
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
Private Declare Function UnhookWindowsHookEx Lib "user32" (ByVal hHook As Long) As Long
Private Declare Function CallNextHookEx Lib "user32" (ByVal hHook As Long, ByVal nCode As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDest As Any, pSource As Any, ByVal cb As Long)
Private Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Long) As Integer
Public value As String
Public active As Boolean
Public Function HookKeyboard() As Long
On Error GoTo ErrorHookKeyboard
m_hDllKbdHook = SetWindowsHookEx(WH_KEYBOARD_LL, AddressOf LowLevelKeyboardProc, App.hInstance, 0&)
HookKeyboard = m_hDllKbdHook
Exit Function
ErrorHookKeyboard:
MsgBox Err & ":Error in call to HookKeyboard()." _
& vbCrLf & vbCrLf & "Error Description: " & Err.Description, vbCritical, "Warning"
Exit Function
End Function
Public Sub UnHookKeyboard()
On Error GoTo ErrorUnHookKeyboard
UnhookWindowsHookEx (m_hDllKbdHook)
Exit Sub
ErrorUnHookKeyboard:
MsgBox Err & ":Error in call to UnHookKeyboard()." _
& vbCrLf & vbCrLf & "Error Description: " & Err.Description, vbCritical, "Warning"
Exit Sub
End Sub
Public Function LowLevelKeyboardProc(ByVal nCode As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Static kbdllhs As KBDLLHOOKSTRUCT
If nCode = HC_ACTION Then
Call CopyMemory(kbdllhs, ByVal lParam, Len(kbdllhs))
If active Then
MsgBox ("keypressed")
End If
End If
I just need to call HookKeyboard/UnhookKeyboard in the main form