Windows API in a Sub Function [VBA]

Question

I am new to VBA therefore please excuse me in advance if my question is silly. That said, I have the following Windows API:

Private Declare PtrSafe Function IsIconic Lib "user32" (ByVal hWnd As LongPtr) As Integer

and inside the module where we have declared the API I have the following function:

Function IsMinimized(hWndAccessApp As Long) As Boolean
    IsMinimized = IsIconic(hWndAccessApp) * -1
End Function

In addition to that I also have a form that has a button and a click event on that button that looks like:

Private Sub btn_one_Click()
    Dim test As Boolean
    test = IsMinimized(hWndAccessApp)
    MsgBox test
End Sub

And everything is working perfectly. However, I was wondering if there is a way to skip the function inside the module and call the "IsIconic" API directly from the Private Sub associated with the button inside the form?

If it works the why you wrote (using a wrapper function, I see no reason why it shouldn't work when calling it directly - have you tried? Personally, I think using a wrapper Function is a good idea. — FunThomas, Jan 19 '22 at 17:03
@FunThomas - Whenever I try with `Dim test As Boolean` and `test = IsIconic(hWndAccessApp) * -1` it gives me that `IsIconic Sub or Function is not defined` and I am not sure how to define it further than adding `Private Declare PtrSafe Function IsIconic...` inside a module. To be completely honest I agree with you, but there is not really a real case behind this. I am just playing around with functions and subs as an exercise more than anything else. — George Smith, Jan 19 '22 at 17:37

score 1 · Accepted Answer · answered Jan 19 '22 at 17:58

a) There is no way to avoid the Declare-Statement for an API function.

b) You have defined your IsIconic-declaration as Private, therefore it is known only in that module. If the code of btn_one_Click is not in that module, it cannot access the function - but that has nothing to do with being an API function. Just remove the Private-keyword, and you can access it from "everywhere".

c) As already mentioned in the comments, I think it is a good idea to use a wrapper function that hides the details of the API-call (and the conversion of the integer value that is returned into an boolean).

d) Using IsIconic(hWndAccessApp) * -1 to convert an Integer-Value 1 to a boolean looks dirty to me. To avoid a calculation to get a boolean, I would suggest to use

IsMinimized = (IsIconic(hWndAccessApp) <> 0)     ' Or = 1

In almost all cases, you should forget about the fact that a boolean is stored as 0 and -1 for False and True. Let VBA do the conversion from 1 to True for you.

Oh, I am not seeing where my mistake was. Thank you for pointing it out, I really appreciate it. In addition, I have moved away from `* - 1` and instead picked what you have suggested. Once again, thank you for the help! — George Smith, Jan 19 '22 at 20:17

Windows API in a Sub Function [VBA]

1 Answers1