VBA & API - Strange problem using

[Philip]

Hi all,

I have a 'Please wait' form that shows a progress bar, and messages to the
user. I am using the below code to hide the title-bar on window Initialise:

>>> CODE>>>>
Private Sub UserForm_Initialize()

lFrmHdl = FindWindowA(vbNullString, Me.Caption)
ShowTitleBar False

Me.Show vbModeless

End Sub

Public Function ShowTitleBar(ByVal bState As Boolean)
Dim lStyle As Long
Dim tR As RECT

'// Get the window's position:
GetWindowRect lFrmHdl, tR

'// Modify whether title bar will be visible:
lStyle = GetWindowLong(lFrmHdl, GWL_STYLE)
'
If Not bState Then
lStyle = lStyle And Not WS_SYSMENU
lStyle = lStyle And Not WS_MAXIMIZEBOX
lStyle = lStyle And Not WS_MINIMIZEBOX
lStyle = lStyle And Not WS_CAPTION
blnTitleVisible = True
Else
lStyle = lStyle Or WS_SYSMENU
lStyle = lStyle Or WS_MAXIMIZEBOX
lStyle = lStyle Or WS_MINIMIZEBOX
lStyle = lStyle Or WS_CAPTION
blnTitleVisible = False
End If

SetWindowLong lFrmHdl, GWL_STYLE, lStyle

'// Ensure the style takes and make the window the
'// same size, regardless that the title bar
'// is now a different size:
SetWindowPos lFrmHdl, 0, tR.Left, tR.Top, tR.Right - tR.Left, tR.Bottom -
tR.Top, _
SWP_NOREPOSITION Or SWP_NOZORDER Or SWP_FRAMECHANGED

End Function

<<< END CODE <<<<

My problem is, somewhere there must be a memory leak or something because I
get an 'The object invoked has disconnected from it's clients' error followed
by a crash of Excel...

The strange thing is, this all works fine with my splash form, it's just
with the wait form that runs during the macro that there is a problem.

Is there anyway to ignore that error?

thanks

Philip

[Leith Ross]

Hello Phillip,

You have violated one of the most basic API rules - Never Store A Window Handle in a Variable!!!

The reason is window handles are recycled as threads and processes are created and destroyed. To use the API sucessfully requires dilligence to detail. This is a very powerful platform and not VB or VBA which is designed to protect you from yourself. The API has virtually no safeguards, which can lead to major system corruption when it fails.

The VBA in Office 2000 and later provide you with the window handle property for the UserForm, no API call needed.

To Get the Window Handle of a Form:
UserForm1.Hwnd or Me.Hwnd

The best advice about using the API is, If you don't know what it does and what it effects DON"T USE IT.

Sincerely,
Leith Ross