by Evripidis (1 Submission)
Category: Windows API Call/Explanation
Difficulty: Intermediate
Date Added: Wed 3rd February 2021
Rating: 
(6 Votes)
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 DeclarationsPrivate 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
VBcoders'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
