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Peter T Peter T is offline
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Default Why doesn't this recursive function return the right value?

Re your last 4 posts:

2/4
It looks you can indeed simplify by getting rid of 2 variables and just

keep
the extra
one nHolder (which I renamed to lHolder):


Exactly. But I'm surprised your tester() msgbox in this post (as quoted
below) shows a value, I would have expected you would need to do -

Dim n as long
call FindWindowHwndLike_B(0, "Static", "DOB", 0, n)
Msgbox n

To clarify what I should have done previously, in my demo altogether I
introduced 4 var's vs your original.

Passed to the function
bUsetmpVar : purely for testing two methods whereby the function returns a
value, or does not (like your original).
nHold : the ByRef arg

Declared in the function
nTmp & nResult

Simply the ByRef nHold arg works fine, though of course the function may not
return a value (depends on levels of recursions). With this method get rid
of nTmp & nResult and don't rely on the function returning a value.

However, if you want the function to consistently return a value, then use
nTmp & nResult and can dispense with the ByRef nHold arg.

With your recursive routine both methods work, I suspect the byRef arg
faster. However some routines may dictate one or other, or even both
methods.

nHolder (which I renamed to lHolder):


Guess I ought to get out of my "n" convention for longs, and adapt to the
rest of the world and use an l !

============

3/4 Text Compare etc
I want it case-sensitive, so that is OK.
Couldn't find anything for the ClassName comparison.


I don't quite follow. If you want case-sensitive nothing is required and NOT
Option Text (Option Compare Binary ?)

============

4/4
Actually it can be speeded up further by declaring everything ByRef:


Yes ByRef is always faster, though depending on the routine ByVal might be
required for some var's.

============

FWIW, for enumerating all windows this is probably faster (XL2K or later)

Public Declare Function EnumWindows Lib "user32" _
(ByVal lpEnumFunc As Long, ByVal lParam As Long) As Boolean

EnumWindows AddressOf MyFunc, ByVal 0&
then in MyFunc return value to a module/public variable

though probably not appropriate for your particular "get out when got
something" routine.

Regards,
Peter T

PS, not sure if you noticed but I posted a question minutes after your OP,
it's still looking very solitary !


"RB Smissaert" wrote in message
...
Actually it can be speeded up further by declaring everything ByRef:

Function FindWindowHwndLike(hWndStart As Long, _
ClassName As String, _
WindowTitle As String, _
level As Long, _
lHolder As Long) As Long

RBS

"Peter T" <peter_t@discussions wrote in message
...
How and where are nTmp and nResult declared?


Sorry, I should have stated within the FindWindowHwndLike function

Following attempts to demonstrate the two methods I mentioned earlier -
- an additional ByRef var to pass back to the calling routing
- re-assigning the value to the Function on each return back up the

stack

requires the same API's & Const's per your OP, maybe also Compare Text
(just
in case)

Option Compare Text

Sub tester2()
Dim s1 As String, s2 As String
Dim x As Long, y As Long

s1 = "EXCE": s2 = "Book" ' eg like EXCEL7 & Book1.xls

x = FindWindowHwndLike_B(0, s1, s2, 0, y, False)
MsgBox "Func-return " & x & vbCr & "ByRef Arg " & y

x = FindWindowHwndLike_B(0, s1, s2, 0, y, True)
MsgBox "Func-return " & x & vbCr & "ByRef Arg " & y

End Sub

Function FindWindowHwndLike_B(ByVal hWndStart As Long, _
ByVal ClassName As String, _
ByVal WindowTitle As String, _
ByVal level As Long, _
ByRef nHold As Long, _
bUseTmpVar As Boolean) As Long

'finds the first window where the class name start with ClassName
'and where the Window title starts with WindowTitle, returns Hwnd
'-----------------------------------------------------------------
Dim hwnd As Long
Dim sWindowTitle As String
Dim sClassName As String
Dim r As Long
Dim nTmp As Long
Dim nResult As Long

'Initialize if necessary. This is only executed
'when level = 0 and hWndStart = 0, normally
'only on the first call to the routine.
If level = 0 Then
If hWndStart = 0 Then
hWndStart = GetDesktopWindow()
End If
End If

'Increase recursion counter
level = level + 1

'Get first child window
hwnd = GetWindow(hWndStart, GW_CHILD)

Do Until hwnd = 0

'Search children by recursion

If bUseTmpVar Then
nTmp = FindWindowHwndLike_B(hwnd, ClassName, WindowTitle, _
level, nHold, bUseTmpVar)
If nTmp Then nResult = nTmp
Else
Call FindWindowHwndLike_B(hwnd, ClassName, WindowTitle, _
level, nHold, bUseTmpVar)
End If

'Get the window text
sWindowTitle = Space$(255)
r = GetWindowText(hwnd, sWindowTitle, 255)
sWindowTitle = Left$(sWindowTitle, r)

'get the class name
sClassName = Space$(255)
r = GetClassName(hwnd, sClassName, 255)
sClassName = Left$(sClassName, r)

'Check if the window matches the search parameters
If (sWindowTitle Like "*" & WindowTitle & "*") And _
(sClassName Like ClassName & "*") Then
FindWindowHwndLike_B = hwnd
nHold = hwnd
Exit Function
End If

'Get next child window
hwnd = GetWindow(hwnd, GW_HWNDNEXT)

Loop
If bUseTmpVar Then
FindWindowHwndLike_B = nResult
End If
End Function

Regards,
Peter T


"RB Smissaert" wrote in message
...
Hi Peter,


Sorry, but I don't understand this bit at all:

'recursive
nTmp = FindWindowHwndLike(hwnd, ClassName, WindowTitle, level)
If nTmp Then nResult = nTmp

'then finally -
FindWindowHwndLike = nResult
Exit function

How and where are nTmp and nResult declared?
Why would it make a difference?
I tried something like you suggested, but still get zero.

What I don't understand is this: It finds the right window, with the
right
hwnd, but it returns zero.
Where does the variable hwnd change from the right value to zero?
I put messageboxes in the recursive function that could show after the

right
window was found, but nil of these show, so no code runs after the

window
was found:


Function FindWindowHwndLike(ByVal hWndStart As Long, _
ByVal ClassName As String, _
ByVal WindowTitle As String, _
ByVal level As Long) As Long

'finds the first window where the class name start with ClassName
'and where the Window title starts with WindowTitle, returns Hwnd
'-----------------------------------------------------------------
Dim hwnd As Long
Dim sWindowTitle As String
Dim sClassName As String
Dim r As Long
Dim bFound As Boolean

If bFound Then
MsgBox "test1"
End If

'Initialize if necessary. This is only executed
'when level = 0 and hWndStart = 0, normally
'only on the first call to the routine.
If level = 0 Then
If hWndStart = 0 Then
hWndStart = GetDesktopWindow()
End If
End If

'Increase recursion counter
level = level + 1

'Get first child window
hwnd = GetWindow(hWndStart, GW_CHILD)

If bFound Then
MsgBox "test2"
End If

Do Until hwnd = 0

If bFound Then
MsgBox "test3"
End If

'Search children by recursion
FindWindowHwndLike hwnd, ClassName, WindowTitle, level

'Get the window text
sWindowTitle = Space$(255)
r = GetWindowText(hwnd, sWindowTitle, 255)
sWindowTitle = Left$(sWindowTitle, r)

'get the class name
sClassName = Space$(255)
r = GetClassName(hwnd, sClassName, 255)
sClassName = Left$(sClassName, r)

'Check if the window matches the search parameters
If (sWindowTitle Like "*" & WindowTitle & "*") And _
(sClassName Like ClassName & "*") Then

If bFound Then
MsgBox "test4"
End If

bFound = True
MsgBox hwnd
FindWindowHwndLike = hwnd
Exit Function
If bFound Then
MsgBox "test5"
End If

End If

If bFound Then
MsgBox "test6"
End If

'Get next child window
hwnd = GetWindow(hwnd, GW_HWNDNEXT)

If bFound Then
MsgBox "test7"
End If

Loop

If bFound Then
MsgBox "test8"
End If

End Function


The trouble probably is that recursive function are bit mind-boggling

in
any
case and I might be overlooking something simple here.
I just know that in my particular situation I don't have to worry about

more
than one qualifying windows.
Thanks in any case for your suggestions.


RBS


"Peter T" <peter_t@discussions wrote in message
...
Hi Bart,

My take is the function return value persists only in the calling
stack.

So two solutions, the first as you've described and include an

additional
ByRef arg to return the value all the way back to the original

calling
routine. Or something like this:

'recursive
nTmp = FindWindowHwndLike(hwnd, ClassName, WindowTitle, level)
If nTmp Then nResult = nTmp

'then finally -
FindWindowHwndLike = nResult
Exit function

I think passing the additional ByRef arg would be faster.

Just a thought, maybe build an array of all the "like" window

captions,
just
in case more than one.

Regards,
Peter T



"RB Smissaert" wrote in message
...
Have a recursive function that returns the window handle of a

particular
window, based on the window type and text.
It works fine and it finds the right window, but it just doesn't
return
the
right value. It returns zero.
When I do a msgbox before the Exit function it shows fine, or when I
retrieve the value with a private variable I get the right value as

well.
It
is not a problem, but just wondering why this happens.

Option Explicit
Private Declare Function GetDesktopWindow Lib "user32" () As Long
Private Declare Function GetWindow Lib "user32" _
(ByVal hwnd As Long, _
ByVal wCmd As Long) As Long
Private Declare Function GetWindowText Lib "user32" _
Alias "GetWindowTextA" _
(ByVal hwnd As Long, _
ByVal lpString As String, _
ByVal cch As Long) As Long
Private Declare Function GetClassName Lib "user32" _
Alias "GetClassNameA" _
(ByVal hwnd As Long, _
ByVal lpClassName As String, _
ByVal nMaxCount As Long) As

Long
Private Const GW_HWNDFIRST = 0
Private Const GW_HWNDLAST = 1
Private Const GW_HWNDNEXT = 2
Private Const GW_HWNDPREV = 3
Private Const GW_OWNER = 4
Private Const GW_CHILD = 5

Sub tester()
MsgBox FindWindowHwndLike(0, "Static", "DOB", 0)
End Sub


Function FindWindowHwndLike(ByVal hWndStart As Long, _
ByVal ClassName As String, _
ByVal WindowTitle As String, _
ByVal level As Long) As Long

'finds the first window where the class name start with

ClassName
'and where the Window title starts with WindowTitle, returns

Hwnd

'-----------------------------------------------------------------
Dim hwnd As Long
Dim sWindowTitle As String
Dim sClassName As String
Dim r As Long

'Initialize if necessary. This is only executed
'when level = 0 and hWndStart = 0, normally
'only on the first call to the routine.
If level = 0 Then
If hWndStart = 0 Then
hWndStart = GetDesktopWindow()
End If
End If

'Increase recursion counter
level = level + 1

'Get first child window
hwnd = GetWindow(hWndStart, GW_CHILD)

Do Until hwnd = 0

'Search children by recursion
Call FindWindowHwndLike(hwnd, ClassName, WindowTitle, level)

'Get the window text
sWindowTitle = Space$(255)
r = GetWindowText(hwnd, sWindowTitle, 255)
sWindowTitle = Left$(sWindowTitle, r)

'get the class name
sClassName = Space$(255)
r = GetClassName(hwnd, sClassName, 255)
sClassName = Left$(sClassName, r)

'Check if the window matches the search parameters
If (sWindowTitle Like "*" & WindowTitle & "*") And _
(sClassName Like ClassName & "*") Then
FindWindowHwndLike = hwnd
Exit Function
End If

'Get next child window
hwnd = GetWindow(hwnd, GW_HWNDNEXT)

Loop

End Function


Thanks for any advice.


RBS