[RESOLVED] Problem with FindWindow API

[oprache]

I use ShellExecute to launch an application from VB6. I then use FindWindow to get the application's window handle. Using Spy++ I know the class and the window caption, which I input into the FindWindow call.
What happens is that FindWindow returns 0 and no window caption BUT, if I start a new instance of the application (by clicking on a launch button whose click procedure does the ShellExecute), then FindWindow returns a handle of the first instance. This is very reproducible but certainly not what I am after.
Below is the code I have in my command click procedure:

Private Sub Command1_Click()
Dim r As Long 'Variable to store the response string
Dim buffer As String
Dim numChars As Integer
Dim hwndPHD As Long

r = ShellExecute(0, "Open", "C:\Program Files\PHDGuiding\PHD.exe", 0, 0, SW_SHOWNORM)
lbltask_ID.Caption = Hex$(r)
hwndPHD = FindWindow("wxWindowClassNR", "PHD Guiding 1.10.0 - www.stark-labs.com (Log active)")

'Debug.Print Hex$(hwndPHD)
If hwndPHD <> 0 Then
' Init buffer
buffer = Space$(128)
' Get caption of window
numChars = GetWindowText(hwndPHD, buffer, Len(buffer))
lblhWnd.Caption = Hex$(hwndPHD)
' Display window's caption
lblWinCaption.Caption = Left$(buffer, numChars)
End If
End Sub


All the API declarations are done in a control module and I get no error when running the application in the IDE.
I do not understand what is going on and will welcome any insight
Thanks
Olivier

[Billy Conner]

well this probably isn't the problem, but i do see a programming situation to avoid.. GetWindowText API should return a LONG integer for any win32 OS, you dimmed numChars as integer.

also you may want to put some do of loop to wait so many seconds for the Shell'd app to load the window with a doevents before you attempt to find it.
simple example..

Dim st As Single
Dim numChars As Long

st = Timer
Do
    Doevents  <--- EDIT: placed the 'obvious' i mentioned above into my code
    numChars = GetWindowText(hwndPHD, buffer, Len(buffer))
Loop Until numChars Or (Timer - st >= 2)

[oprache]

Thanks.
I found my problem. I thought it was timing related and added a delay but that did not do it. The solution was to place a Do Events and a loop polling FindWindow until it returned a non zero value. It now works fine.
I also corrected the numChars formatting, thanks for the input
Olivier