GetWindow, FindWindow, EnumWindow, and EgtWindowX

[hatman]

So I have a solution that works (though it isn't quite as bullet-proof as I would like). What I am interested in is an explanation why NONE of the seemingly more bullet-proof solutions work.

In controlling Excel from a VB 6.0 application, at some point, the user can display the Format Axis dialog of the Excel instance, which is done programmatically using the Dialogs().Show method. The problem comes in where I need to halt the recalculation before the dialog is displayed, and resume recalc after it is manually closed. Oh, and the user may have other instances of the Excel Application open, not under of the VB 6.0 application. To do this, i need teh HWND of the Format Axis window, then periodically monitor it unil it is closed.

My first approach was to use the HWND of the XLMAIN window to find the appropriate child window. But after 3 different methods (some of which I later read in various articles actually call EnumWindows in teh background anyway, so perhaps they aren't as unique as I thought) I determined that the Format Axis window isn't visible as a child. WHY NOT???

The FindWindow function works to find the most recently created inistance of the window, which is probably fine, since it gets called immediately after the instance I am looking for is created, making it extremely unlikely to get stuck with the wrong instance.

Option Explicit
Private Declare Function EnumChildWindows _
    Lib "user32" _
    (ByVal hWndParent As Long, _
    ByVal lpEnumFunc As Long, _
    ByVal lParam As Long) As Long
    
Public Declare Function GetClassName _
    Lib "user32" Alias "GetClassNameA" _
    (ByVal hwnd As Long, _
    ByVal lpClassName As String, _
    ByVal nMaxCount As Long) As Long
    
Public Declare Function GetWindowText _
    Lib "user32" Alias "GetWindowTextA" _
    (ByVal hwnd As Long, _
    ByVal lpString As String, _
    ByVal cch As Long) As Long
    
Public Declare Function GetWindowTextLength _
    Lib "user32" Alias "GetWindowTextLengthA" _
    (ByVal hwnd As Long) As Long
    
Public Declare Function FindWindow _
    Lib "user32" Alias "FindWindowA" _
    (ByVal lpClassName As String, _
    ByVal lpWindowName As String) As Long
    
Public Declare Function GetParent _
    Lib "user32.dll" _
    (ByVal hwnd As Long) As Long
    
Public Declare Function FindWindowX _
    Lib "user32" Alias "FindWindowExA" _
    (ByVal hWnd1 As Long, _
    ByVal hWnd2 As Long, _
    ByVal lpsz1 As Long, _
    ByVal lpsz2 As Long) As Long
    
Public Declare Function GetWindow _
    Lib "user32" _
    (ByVal hwnd As Long, _
    ByVal wCmd As Long) As Long
Private Const GW_CHILD = 5
Private Const GW_HWNDNEXT = 2
Private Const GW_HWNDPREV = 3
Dim windows() As Long
Dim windowsCount As Long
Sub Compare_Them_All()
    Sheet3.Rows.Clear
    Chart4.Activate
    
    Chart4.Axes(xlPrimary).Select
    
    Application.Dialogs(xlDialogFormatLegend).Show
    Call EnumWindow_Method
    
    Call FindWindowX_Method
    
    Call FindWindow_Method
    
    Call GetWindow_Method
End Sub
Sub EnumWindow_Method()
    Dim a() As Long
    Dim cnt As Long
    Dim sClass As String
    Dim getwindowclass As String
    Dim ControlText As String
    
    sClass = Space$(256)
    GetClassName Application.hwnd, sClass, 255
    getwindowclass = Left$(sClass, InStr(sClass, vbNullChar) - 1)
    
    ControlText = String(GetWindowTextLength(Application.hwnd) + 1, Chr$(0))
    GetWindowText Application.hwnd, ControlText, Len(ControlText)
    
    Sheet3.Range("A1").Value = Application.hwnd
    Sheet3.Range("B1").Value = getwindowclass
    Sheet3.Range("C1").Value = ControlText
    
    
    a = ChildWindows(Application.hwnd)
    
    For cnt = 1 To UBound(a, 1)
    
        sClass = Space$(256)
        GetClassName a(cnt), sClass, 255
        getwindowclass = Left$(sClass, InStr(sClass, vbNullChar) - 1)
        
        ControlText = String(GetWindowTextLength(a(cnt)) + 1, Chr$(0))
        GetWindowText a(cnt), ControlText, Len(ControlText)
        
        Sheet3.Range("A" & cnt + 1).Value = a(cnt)
        Sheet3.Range("B" & cnt + 1).Value = getwindowclass
        Sheet3.Range("C" & cnt + 1).Value = ControlText
        
    Next cnt
End Sub
Function ChildWindows(ByVal hwnd As Long) As Long()
    windowsCount = 0
    
    EnumChildWindows hwnd, AddressOf EnumWindows_CBK, 1
    
    ReDim Preserve windows(windowsCount) As Long
    
    ChildWindows = windows()
    
End Function

Private Function EnumWindows_CBK(ByVal hwnd As Long, ByVal lParam As Long) As Long
    
    If windowsCount = 0 Then
    
        ReDim windows(100) As Long
        
    ElseIf windowsCount >= UBound(windows) Then
    
        ReDim Preserve windows(windowsCount + 100) As Long
        
    End If
    
    
    windowsCount = windowsCount + 1
    
    windows(windowsCount) = hwnd
    
    EnumWindows_CBK = 1
    
End Function
Sub FindWindowX_Method()
    Dim hChild As Long
    Dim cnt As Long
    Dim sClass As String
    Dim getwindowclass As String
    Dim ControlText As String
    
    hChild = FindWindowX(Application.hwnd, 0, 0, 0)
    
    cnt = 2
    
    Do
       
        sClass = Space$(256)
        GetClassName hChild, sClass, 255
        getwindowclass = Left$(sClass, InStr(sClass, vbNullChar) - 1)
        
        ControlText = String(GetWindowTextLength(hChild) + 1, Chr$(0))
        GetWindowText hChild, ControlText, Len(ControlText)
        
        Sheet3.Range("E" & cnt).Value = hChild
        Sheet3.Range("F" & cnt).Value = getwindowclass
        Sheet3.Range("G" & cnt).Value = ControlText
        
        hChild = FindWindowX(Application.hwnd, hChild, 0, 0)
       
       cnt = cnt + 1
       
    Loop Until hChild = 0
End Sub
Sub FindWindow_Method()
    Dim DialogHwnd As Long
    Dim parent_h As Long
    Dim sClass As String
    Dim getwindowclass As String
    Dim ControlText As String
    
    'this one only gets the MOST RECENT instance.
    
    DialogHwnd = FindWindow("NUIDialog", "Format Axis")
    
    parent_h = GetParent(DialogHwnd)
    
    sClass = Space$(256)
    GetClassName DialogHwnd, sClass, 255
    getwindowclass = Left$(sClass, InStr(sClass, vbNullChar) - 1)
    
    ControlText = String(GetWindowTextLength(DialogHwnd) + 1, Chr$(0))
    GetWindowText DialogHwnd, ControlText, Len(ControlText)
    
    Sheet3.Range("M2").Value = DialogHwnd
    Sheet3.Range("N2").Value = getwindowclass
    Sheet3.Range("O2").Value = ControlText
    
    sClass = Space$(256)
    GetClassName parent_h, sClass, 255
    getwindowclass = Left$(sClass, InStr(sClass, vbNullChar) - 1)
    
    ControlText = String(GetWindowTextLength(parent_h) + 1, Chr$(0))
    GetWindowText parent_h, ControlText, Len(ControlText)
    
    Sheet3.Range("M1").Value = parent_h
    Sheet3.Range("N1").Value = getwindowclass
    Sheet3.Range("O1").Value = ControlText
End Sub
Sub GetWindow_Method()
    Dim lngSrch As Long
    Dim ControlText As String
    Dim sClass As String
    Dim getwindowclass As String
    Dim cnt As Integer
    
    lngSrch = Application.hwnd
    
    lngSrch = GetWindow(lngSrch, GW_CHILD)
    
    cnt = 2
    
    Do
        lngSrch = GetWindow(lngSrch, GW_HWNDNEXT)
        
        If lngSrch = 0 Then
        
            Exit Do
            
        End If
        
        ControlText = String(GetWindowTextLength(lngSrch) + 1, Chr$(0))
        GetWindowText lngSrch, ControlText, Len(ControlText)
        
        sClass = Space$(256)
        GetClassName lngSrch, sClass, 255
        getwindowclass = Left$(sClass, InStr(sClass, vbNullChar) - 1)
        
        Sheet3.Range("I" & cnt).Value = lngSrch
        Sheet3.Range("J" & cnt).Value = getwindowclass
        Sheet3.Range("K" & cnt).Value = ControlText
        
        cnt = cnt + 1
        
    Loop
End Sub

 

[RoryA]

As far as I can tell the parent of the dialog window is actually the VBE window, so once you have the dialog handle you can use GetParent to test if the parent is the VBE for your application.
For some reason, using FindWindowEx (or FindWindowX in your case) and specifying the VBE handle as the first argument does not work.

 

[hatman]

Can you explain why you say that the parent of the Format Axis dialog is the VBE? When I use GetParent on the Dialog, it returns the XLMain Window.

: getwindowclass_parent : "XLMAIN" : String
: ControlText_parent : "Microsoft Excel - Book2
" : String

 

[RoryA]

It might be because I was stepping through the code in the VBE. If you know the parent is always XLMAIN, then you don't have a problem.

 

[hatman]

I agree in part. Using FindWindow, only the most recently created instance is returned. I can take the HWND returned (as you suggest), get the parent, and validate it against the XLMain, to verify that I have the correct instance of the dialog. As far as I can tell, that works fine. And as I stated in the origonal post: I can live with that solution, for all cases where the most recently created instance is in fact the one I am interested in. But what if it is not? I can't forsee a scenario where this would be an issue, but just because I can't forsee it does not mean it can't happen. In that case, FindWindow won't locate the "next" instance. While I'd like a more bullet-proof solution for this case, I think I can probably live without it.

Though I am still curious why, if XLMain is the parent of the dialog, none of the other three methods detect the dialog as a child of XLMain.

I guess I was trying to start a discussion (albeit extremely geeky), not necessarily elicit a solution to a particular problem (hence a Lounge post, rather than in the Questions forum).

I'd be interested in any other thoughts/theories...

 

[RoryA]

You should be able to use FindWindowEx to find the next instance of the dialog, should one exist, then check its parent handle.

As to why it is the way it is, I suspect they ****ed something up when they made the dialogs modeless in 2007.

 

[hatman]

You should be able to use FindWindowEx to find the next instance of the dialog, should one exist, then check its parent handle.

That's what I thought. Passing the XLMain HWND as the argument for the parent window does not yield the Format Axis dialog (as shown in the code I posted). When the parent window is omitted, of course, the function searches within windows that are children of the desktop, which the Format Axis dialog is not, so again, it is not found.

As to why it is the way it is, I suspect they ****ed something up when they made the dialogs modeless in 2007.

That's probably the best answer I'm liable to get... I hadn't thought of that.

 

[RoryA]

When the parent window is omitted, of course, the function searches within windows that are children of the desktop, which the Format Axis dialog is not, so again, it is not found.

that's how I found it. Used 0& as the first two arguments.

 

[hatman]

Interesting. When I tried FindWindowEx before, I passed the Desktop HWND as retrieved using the GetDesktopWindow API (cause that's teh usage/example I found on teh net). That caused it to parse only the top level windows. At which point, I changed to pass in the XLMain as the parent window, which failed to yield the dialog. But leaving the argument as a null causes it to parse the lower level windows also, as I now see.

Thanx Rory! My new code looks more like this:

Function Get_Format_Axis_HWND(XLMAin_hwnd As Long) As Long
    Dim hChild As Long
    
    hChild = FindWindowX(0&, 0&, "NUIDialog", "Format Axis")
    
    Do Until GetParent(hChild) = XLMAin_hwnd Or hChild = 0
       
        hChild = FindWindowX(0&, hChild, "NUIDialog", "Format Axis")
       
    Loop
    
    Get_Format_Axis_HWND = hChild
End Function

 

[Jaafar Tribak]

Hi hatman.

I don't have Excel 2007 so I couldn't test the code. However I would take a different approach specially if there is a scenario where different instances could be open simultaniously.

I would install a CBT hook immediately before calling the Format Axis Dialogue window and watch for the HCBT_DESTROYWND hook ID which indicates that the Axis Format window has been closed.

This approach avoids the need to loop through endless windows plus will always return the desired instance.

Something like this :

Option Explicit
 
Private Declare Function FindWindow Lib "user32.dll" _
Alias "FindWindowA" (ByVal lpClassName As String, _
ByVal lpWindowName As String) As Long
 
Private Declare Function GetWindowLong Lib "user32" _
Alias "GetWindowLongA" ( _
ByVal hwnd As Long, _
ByVal nIndex As Long) As Long
 
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 CallNextHookEx Lib "user32" _
(ByVal hHook As Long, _
ByVal nCode As Long, _
ByVal wParam As Long, _
lParam As Any) As Long
 
Private Declare Function UnhookWindowsHookEx Lib "user32" _
(ByVal hHook As Long) As Long
 
Private Declare Function GetCurrentThreadId Lib "kernel32" _
() As Long
 
Private Declare Function GetClassName Lib "user32.dll" _
Alias "GetClassNameA" _
(ByVal hwnd As Long, _
ByVal lpClassName As String, _
ByVal nMaxCount As Long) As Long
 
Private Const WH_CBT As Long = 5
Private Const HCBT_DESTROYWND = 4
Private Const GWL_HINSTANCE As Long = (-6)
 
Private lCBTHook  As Long
 
Sub Test()
 
    Sheet3.Rows.Clear

    Chart4.Activate
    
    Chart4.Axes(xlPrimary).Select
 
    lCBTHook = SetWindowsHookEx(WH_CBT, AddressOf CBTProc, _
    GetAppInstance, GetCurrentThreadId)
 
    Application.Dialogs(xlDialogFormatLegend).Show
 
End Sub
 
 
Private Function CBTProc _
(ByVal idHook As Long, ByVal wParam As Long, _
ByVal lParam As Long) As Long
 
    Dim sBuffer As String
    Dim lRetVal As Long
 
 
    Select Case idHook
 
        Case Is = HCBT_DESTROYWND 'a Wnd has been closed.
 
            'if so, is it our Format Axis wnd ?
            sBuffer = Space(256)
            lRetVal = GetClassName(wParam, sBuffer, 256)
 
            If Left(sBuffer, lRetVal) = "NUIDialog" Then
 
                'it's our Format Axis wnd. Remove the CBT hook now.
                UnhookWindowsHookEx lCBTHook
 
                MsgBox "The Format Axis Window has been close." & _
                vbNewLine & "You can resume calculation now."
 
            End If
 
    End Select
 
    CBTProc = CallNextHookEx _
    (lCBTHook, idHook, ByVal wParam, ByVal lParam)
 
End Function
 
 
Private Function GetAppInstance() As Long
 
    GetAppInstance = GetWindowLong _
    (FindWindow("XLMAIN", Application.Caption), GWL_HINSTANCE)
 
End Function

Note that the hook is immediatly removed upon closing the Format Axis Dialogue so it won't have a bad impact on performance or code stability.