Visual Basic Programming Code Examples

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Returning the parent windows owned by a process



Returning the parent windows owned by a process

The following code demonstrates how to return all the top level (parent) window handles owned by a specific process ID.

Option Explicit

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As Long, ByVal lpWindowName As Long) As Long
Private Declare Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long
Private Declare Function GetWindowThreadProcessId Lib "user32" (ByVal hwnd As Long, lpdwProcessId As Long) As Long
Private Declare Function GetParent Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function GetCurrentProcessId Lib "kernel32" () As Long
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long


'Purpose     :  Returns a top level (parent) window handle for a specified process ID
'Inputs      :  lProcID             The process ID to return a parent window handle of.
'                                   Note, can be called recursively to retrieve all the
'                                   parent windows owned by a process.
'               [bReturnVisible]    If True only returns top level windows which have the WS_VISIBLE style bit set.
'Outputs     :  Returns the handle of parent window owned by the specified process


Function ProcessToParentWnd(ByVal lProcID As Long, Optional bReturnVisible As Boolean = True) As Long
    Const GW_HWNDNEXT = 2, WS_VISIBLE = &H10000000, GWL_STYLE = (-16)
    Static ssPreviousParents As String, slLastProcID As Long
    
    Dim lTestHwnd As Long, lTestPID As Long, lStyle As Long
    
    If lProcID = 0 Then
        'Reset statics
        ssPreviousParents = ""
        slLastProcID = 0
        Exit Function
    End If
    
    'Find the first window
    lTestHwnd = FindWindow(ByVal 0&, ByVal 0&)
    Do While lTestHwnd <> 0
        'Check if the window isn't a child
        If GetParent(lTestHwnd) = 0 Then
            'Get the window's ProcessID
            Call GetWindowThreadProcessId(lTestHwnd, lTestPID)
            
            If lTestPID = lProcID Then
                If bReturnVisible Then
                    'Do not return hidden windows
                    lStyle = GetWindowLong(lTestHwnd, GWL_STYLE)
                    If (lStyle And WS_VISIBLE) = False Then
                        'Not a visible window
                        lTestPID = -1
                    End If
                End If
            End If
            
            If lTestPID = lProcID Then
                If slLastProcID = lProcID Then
                    'Called with the same proc ID twice
                    If InStr(1, ssPreviousParents, CStr(lTestHwnd) & "|") = 0 Then
                        'Return the next parent handle for this process
                        ProcessToParentWnd = lTestHwnd
                        ssPreviousParents = ssPreviousParents & ProcessToParentWnd & "|"
                        slLastProcID = lProcID
                        Exit Do
                    End If
                Else
                    'New Proc ID
                    ProcessToParentWnd = lTestHwnd
                    ssPreviousParents = ProcessToParentWnd & "|"
                    slLastProcID = lProcID
                    Exit Do
                End If
            End If
        End If
        'retrieve the next window
        lTestHwnd = GetWindow(lTestHwnd, GW_HWNDNEXT)
    Loop
End Function

'Demonstration
Sub Test()
    Dim lParent As Long
    'Retrieve all the parent (top level) window handles owned by this process
    lParent = ProcessToParentWnd(GetCurrentProcessId)
    Debug.Print "Parent window handles owned by this process"
    Do While lParent
        Debug.Print lParent
        lParent = ProcessToParentWnd(GetCurrentProcessId)
    Loop
    'Reset internal statics in function
    ProcessToParentWnd 0
End Sub