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Get window handlle (hWnd) from process ID

A module for retrieving the handle number (hWnd) of a window providing only the process id number (PID). This code is seeking handles that match the given PID and returns the hanlde that refers to a visible window. But, since not all the processes running are windowed or some processes may have multiple windows, may not work for every case.

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

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 GetWindowTextLength Lib "user32" Alias "GetWindowTextLengthA" _
(ByVal Hwnd As Long) As Long

Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
(ByVal Hwnd As Long, ByVal wIndx As Long) As Long

Private Declare Function GetWindowThreadProcessId Lib "user32" _
(ByVal Hwnd As Long, lpdwProcessId As Long) As Long

Rate Get window handlle (hWnd) from process ID

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'EVRIS JAN 2006
'[email protected]
Option Explicit
Private Const GWL_STYLE = (-16)
Private Const GWL_EXSTYLE = (-20)
Private Const WS_VISIBLE = &H10000000
Private Const WS_EX_APPWINDOW = &H40000
Private Type HWND_TEXT
 Window_Handle As Long
 Window_Title As String
End Type
Private ColCounter As Long
Private HandleTextCollection() As HWND_TEXT
Private Declare Function EnumWindows Lib "user32" _
  (ByVal lpEnumFunc As Long, ByVal lParam As Long) As Boolean
  
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 GetWindowTextLength Lib "user32" Alias "GetWindowTextLengthA" _
  (ByVal Hwnd As Long) As Long
  
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
    (ByVal Hwnd As Long, ByVal wIndx As Long) As Long
    
Private Declare Function GetWindowThreadProcessId Lib "user32" _
  (ByVal Hwnd As Long, lpdwProcessId As Long) As Long
Private Function EnumWindowsProc(ByVal Hwnd As Long, ByVal lParam As Long) As Boolean
 Dim Title As String
 Dim r As Long
 
 r = GetWindowTextLength(Hwnd)
 Title = Space(r)
 GetWindowText Hwnd, Title, r + 1
 
 'Add to type array
 ColCounter = ColCounter + 1
 ReDim Preserve HandleTextCollection(ColCounter)
 HandleTextCollection(ColCounter).Window_Handle = Hwnd
 HandleTextCollection(ColCounter).Window_Title = Title
 
 EnumWindowsProc = True
 
End Function
Private Sub EnumAllWindows()
 
 ColCounter = 0
 ReDim HandleTextCollection(0)
 
 EnumWindows AddressOf EnumWindowsProc, ByVal 0&
 
 'At this point, HandleTextCollection() array holds the handles and window titles
 'of all windows enumerated
 
End Sub
Public Function GetWindowHandleFromPID(ByVal AppPID As Long) As Long
 
 Dim AppPID_HWND() As HWND_TEXT   'Will store only handles related to AppPID
 Dim CNT As Long
 Dim HND As Long
 Dim n As Long
 Dim r As Long
 Dim i As Long
 Dim TaskID As Long
 Dim TheHandle As Long
 
 'STEP 1: Find all window handles currently running
 'and put them into HandleTextCollection() array
 Call EnumAllWindows
 
 'STEP 2: Filter handles and keep only theese tha match with AppPID pid number
 'and put them into AppPID_HWND() array
 'GetWindowThreadProcessId returns by reference the PID for each handle given
 CNT = 0
 ReDim AppPID_HWND(0)
 For i = 1 To UBound(HandleTextCollection())
  HND = HandleTextCollection(i).Window_Handle
  n = GetWindowThreadProcessId(HND, TaskID)
  If TaskID = AppPID Then
   'Handle matches AppPID
   CNT = CNT + 1
   ReDim Preserve AppPID_HWND(CNT)
   AppPID_HWND(CNT).Window_Handle = HND
   AppPID_HWND(CNT).Window_Title = HandleTextCollection(i).Window_Title
  End If
 Next i
 
 'STEP 3: From all the handles related to AppPID, search for the handle
 'that refers to a window that is visible.
 For i = 1 To UBound(AppPID_HWND())
  'Must be a visible window
  n = GetWindowLong(AppPID_HWND(i).Window_Handle, GWL_STYLE)
  'And a top-level window onto the taskbar since the window is visible
  r = GetWindowLong(AppPID_HWND(i).Window_Handle, GWL_EXSTYLE)
  If (n) And (WS_VISIBLE) Then
   If (r) And (WS_EX_APPWINDOW) Then
    'Is it the right hWnd ?
    'TODO: GetTitleBarInfo
    TheHandle = AppPID_HWND(i).Window_Handle
    Exit For
   End If
  End If
 Next i
 
 GetWindowHandleFromPID = TheHandle
 
End Function