getting hWnd from a window by name

[Thomas Halsvik]

How do I get the hWnd for a window that i know the name of?
I.e. to activate the Calculator window.

[Yonatan]

First of ALL put this in the general declarations area:

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Next.
If you know a window by its caption (for example, Calculator's caption is "Calculator"), use this:

hWndOfTheWindow = FindWindow(vbNullstring, "Calculator")

If you know a window by its ClassName (for example, Calculator's ClassName is "SciCalc"), use this:

hWndOfTheWindow = FindWindow("SciCalc", vbNullString)

Finding the window by the ClassName is better, because on non-English computers, the caption of Calculator can be different (the word "Calculator" in another language).
The ClassName is always "SciCalc" regardless of the operating system language.

To find ClassNames, use Microsoft's program Spy++ (comes with Visual Studio).

Of course you can just guess random numbers for the hWnd but it's not quite as efficient.

[Thomas Halsvik]

Thanks. It worked. A sub-question. If one only knows the windows name starts with "Calcu" is there a way to get the 1st matching window without doing a enumeration of all the windows?

[Yonatan]

I always complain that Microsoft could have made this thing (finding windows by the beginning of the caption) easier.
Well, they could!

Anyways, put this code in a Module and nowhere else:

Option Explicit

Declare Function EnumWindows Lib "user32" (ByVal lpEnumFunc As Long, ByVal lParam As Long) As Long
Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hWnd As Long, ByVal lpString As String, ByVal cch As Long) As Long

Dim sStart As String
Dim hWndResult As Long
Dim bSensitive As Boolean

Sub TrimNulls(sString As String)
    Dim lPos As Long
    
    lPos = InStr(sString, vbNullChar)
    If lPos > 0 Then sString = Left(sString, lPos - 1)
End Sub

Function EnumWindowsProc(ByVal hWnd As Long, ByVal lParam As Long) As Long
    Dim sCaption As String
    
    sCaption = String(256, vbNullChar)
    Call GetWindowText(hWnd, sCaption, 256)
    Call TrimNulls(sCaption)
    
    If (bSensitive And (sCaption Like sStart & "*")) Or (Not bSensitive And (LCase(sCaption) Like LCase(sStart) & "*")) Then
        hWndResult = hWnd
        Exit Function
    End If
    
    EnumWindowsProc = True
End Function

Function FindWindowByBeginning(ByVal sBeginning As String, Optional ByVal bCaseSensitive As Boolean = False) As Long
    sStart = sBeginning
    bSensitive = bCaseSensitive
    Call EnumWindows(AddressOf EnumWindowsProc, 0)
    FindWindowByBeginning = hWndResult
End Function

Then: (The following code can go anywhere, not just in a module)

' This performs a Case-Insensitive search:
' (Will also find things beginning with CALCU and cAlCu, etc.)
hWndTheWindow = FindWindowByBeginning("Calcu")
' This performs a Case-Sensitive search:
' (Will only find things beginning with Calcu in the exact case)
hWndTheWindow = FindWindowByBeginning("Calcu", True)