VB Forum / COM / November 2008

Hello!
I hope I am in the right newsgroup.
I have a code that relies on the user32.dll.
It uses the SendInput function. I am no SendInput newbie.

This happens quite often (for about 1 of 50 customers):

They use my application for some time, then they suddenly say "It
doesn't work anymore!".
I then send them some test applications to dig down to the problem.
And I found out that the problem is always based on the fact that
SendInput doesn't do what I want.

Yesterday I had a customer who swore to me that he didn't do anything...
he didn't install any software... nothing.

What would you do if this function doesn't do what it should?
Err.LastDLLError is 0.
Oh god, this is so stupid... I don't understand why it always worked,
and then suddenly not.
For me this problem means if I can pay my rent or not.

Public Const KEYEVENTF_KEYUP As Long = &H2
Const KEYEVENTF_KEYDOWN = &H0
Const KEYEVENTF_EXTENDEDKEY = &H1
Const KEYEVENTF_UNICODE = &H4
Const INPUT_KEYBOARD = 1

Private Type KEYBDINPUT
      wVK As Integer
      wScan As Integer
      dwFlags As Long
      Time As Long
      dwExtraInfo As Long
End Type

Public Type INPUT_Type
      dwType As Long
      xi(0 To 23) As Byte
End Type

Public Declare Function SendInput Lib "user32.dll" (ByVal nInputs As
Long, pInputs As INPUT_Type, ByVal cbSize As Long) As Long

Public Sub SendKey(ByVal lKey As Long)
On Error Goto ErrHandler

    Dim inputevents(0 To 1) As INPUT_TYPE
    Dim keyevent As KEYBDINPUT

    With keyevent
        .wVk = 0 '/ wVK must be 0 if dwFlags contains the
KEYEVENTF_UNICODE flag
        .wScan = lKey
        .dwFlags = KEYEVENTF_KEYDOWN Or KEYEVENTF_UNICODE
        .time = 0
        .dwExtraInfo = 0
    End With
    inputevents(0).dwType = INPUT_KEYBOARD
    CopyMemory inputevents(0).xi(0), keyevent, Len(keyevent)

    With keyevent
        .wVk = 0
        .wScan = lKey
        .dwFlags = KEYEVENTF_KEYUP Or KEYEVENTF_UNICODE
        .time = 0
        .dwExtraInfo = 0
    End With
    inputevents(1).dwType = INPUT_KEYBOARD
    CopyMemory inputevents(1).xi(0), keyevent, Len(keyevent)

    Dim l&
    l = SendInput(2, inputevents(0), Len(inputevents(0)))

ErrHandler:
MsgBox "An error occured in function #392347"
End Sub

I don't understand it, and I am afraid it's killing my business if it
don't find the error.
What would you do to find the error?