Sendmessage lvi_getitemtext not working on 64-BITS?

Question

Hello,

 

I am trying to get the position and text of all DeskTop icons, by sending a SendMessage to the desktop's listview, using LVI_GETITEMTEXT. Works oke on 32 bits, but on 64-bits I always get an empty string back. I also tried to do this using LVI_GET_ITEM< but the same result. No errors, but also no text string. (I do get the x,y position of the icon). What is wrong here?

 

Thanks in advance,

 

Option Explicit

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWndParent As Long, ByVal hWndChildAfter As Long, ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function IsWindow Lib "user32" (ByVal hWnd As Long) As Long
Private Declare Function CloseHandle Lib "Kernel32" (ByVal hObject As Long) As Long

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
                            (ByVal hWnd As Long, _
                             ByVal wMsg As Long, _
                             ByVal wParam As Long, _
                             lParam As Any) As Long
                            
Private Const LVM_FIRST = &H1000
Private Const LVM_SETIMAGELIST = (LVM_FIRST + 3)
Private Const LVM_GETITEMCOUNT = (LVM_FIRST + 4)
Private Const LVM_GETITEM = (LVM_FIRST + 5)
Private Const LVM_SETITEM = (LVM_FIRST + 6)
Private Const LVM_INSERTITEM = (LVM_FIRST + 7)
Private Const LVM_DELETEITEM = (LVM_FIRST + 8)
Private Const LVM_GETNEXTITEM = (LVM_FIRST + 12)
Private Const LVM_GETITEMRECT = (LVM_FIRST + 14)
Private Const LVM_SETITEMPOSITION = (LVM_FIRST + 15)
Private Const LVM_GETITEMPOSITION = (LVM_FIRST + 16)
Private Const LVM_HITTEST = (LVM_FIRST + 18)
Private Const LVM_ENSUREVISIBLE = (LVM_FIRST + 19)
Private Const LVM_SCROLL = (LVM_FIRST + 20)
Private Const LVM_ARRANGE = (LVM_FIRST + 22)
Private Const LVM_SETCOLUMNWIDTH = (LVM_FIRST + 30)
Private Const LVM_GETVIEWRECT = (LVM_FIRST + 34)
Private Const LVM_GETORIGIN = (LVM_FIRST + 41)
Private Const LVM_SETITEMSTATE = (LVM_FIRST + 43)
Private Const LVM_GETITEMTEXT = (LVM_FIRST + 45)
Private Const LVM_SETITEMPOSITION32 = (LVM_FIRST + 49)
Private Const LVM_GETWORKAREAS = (LVM_FIRST + 70)

Private Const CB_MAXLVITEMTEXT = 255    ' user-defined, exceptions will happen if not big enough...

Private Type lvItem   ' was LV_ITEM
  mask As Long
  iItem As Long
  iSubItem As Long
  state As Long
  stateMask As Long
  pszText As Long  ' if String, must be pre-allocated
  cchTextMax As Long
  iImage As Long
  lParam As Long
'#If (WIN32_IE >= &H300) Then
  iIndent As Long
'#End If
  iGroupid As Long
  cColumns As Long
  puColumns As Long
End Type

Private Const LVIF_TEXT = &H1
Private Const LVIF_IMAGE = &H2
Private Const LVIF_STATE = &H8

Type POINTAPI
    X As Long
    Y As Long
End Type

Private Enum AccessProtectionFlags
  PAGE_NOACCESS = &H1
'  PAGE_READONLY = &H2
  PAGE_READWRITE = &H4
'  PAGE_WRITECOPY = &H8
  PAGE_EXECUTE = &H10
  PAGE_EXECUTE_READ = &H20
  PAGE_EXECUTE_READWRITE = &H40
'  PAGE_EXECUTE_WRITECOPY = &H80
  PAGE_GUARD = &H100
  PAGE_NOCACHE = &H200
  PAGE_WRITECOMBINE = &H400
End Enum

Private Enum VirtualAllocExTypes   ' commented defs are for APIs other than VirtualAllocEx
  MEM_COMMIT = &H1000
  MEM_RESERVE = &H2000
  MEM_DECOMMIT = &H4000
  MEM_FREE = &H10000
  MEM_RELEASE = &H8000&
'  MEM_public = &H20000
'  MEM_MAPPED = &H40000
  MEM_RESET = &H80000   '  (Win2K oinly)
  MEM_TOP_DOWN = &H100000
'  MEM_WRITE_WATCH = &H200000   ' Win98 only
'  MEM_PHYSICAL = &H400000   ' Win2K only
'  MEM_4MB_PAGES = &H80000000   ' ??
'  SEC_IMAGE = &H1000000
'  MEM_IMAGE = SEC_IMAGE
'  WRITE_WATCH_FLAG_RESET = &H1   ' Win98 only
End Enum

Private Const STANDARD_RIGHTS_REQUIRED = &HF0000
Private Const CB_LVITEM As Long = 36   ' user-defined

' CodePage
Private Const CP_ACP = 0        ' ANSI code page

Private Enum ProcessAccessTypes
  PROCESS_TERMINATE = (&H1)
  PROCESS_CREATE_THREAD = (&H2)
  PROCESS_SET_SESSIONID = (&H4)
  PROCESS_VM_OPERATION = (&H8)
  PROCESS_VM_READ = (&H10)
  PROCESS_VM_WRITE = (&H20)
  PROCESS_DUP_HANDLE = (&H40)
  PROCESS_CREATE_PROCESS = (&H80)
  PROCESS_SET_QUOTA = (&H100)
  PROCESS_SET_INFORMATION = (&H200)
  PROCESS_QUERY_INFORMATION = (&H400)
'  STANDARD_RIGHTS_REQUIRED = &HF0000
  SYNCHRONIZE = &H100000
  PROCESS_ALL_ACCESS = (STANDARD_RIGHTS_REQUIRED Or SYNCHRONIZE Or &HFFF)
End Enum

Private Declare Function GetWindowThreadProcessId Lib "user32" _
                              (ByVal hWnd As Long, _
                               lpdwProcessId As Long) As Long
                              
Private Declare Function OpenProcess Lib "Kernel32" _
                              (ByVal dwDesiredAccess As ProcessAccessTypes, _
                              ByVal bInheritHandle As Long, _
                              ByVal dwProcessId As Long) As Long
                            
Private Declare Function GetCurrentProcessId Lib "Kernel32" () As Long

Private Declare Function VirtualAllocEx Lib "Kernel32" _
                              (ByVal hProcess As Long, _
                              ByVal lpAddress As Long, _
                              ByVal dwSize As Long, _
                              ByVal flAllocationType As VirtualAllocExTypes, _
                              ByVal flProtect As AccessProtectionFlags) As Long
                             
Private Declare Function VirtualFreeEx Lib "Kernel32" _
                              (ByVal hProcess As Long, _
                              ByVal lpAddress As Long, _
                              ByVal dwSize As Long, _
                              ByVal dwFreeType As Long) As Long

                             
Private Declare Function ReadProcessMemory Lib "Kernel32" _
                              (ByVal hProcess As Long, _
                              ByVal lpBaseAddress As Long, _
                              lpBuffer As Any, _
                              ByVal nSize As Long, _
                              lpNumberOfBytesRead As Long) As Long

Private Declare Function WriteProcessMemory Lib "Kernel32" _
                              (ByVal hProcess As Long, _
                              ByVal lpBaseAddress As Long, _
                              lpBuffer As Any, _
                              ByVal nSize As Long, _
                              lpNumberOfBytesWritten As Long) As Long
                             
Private Declare Function lstrlenA Lib "Kernel32" (ByRef lpstring As Long) As Long
                           
Private Declare Function MultiByteToWideChar Lib "Kernel32" _
                           (ByVal CodePage As Long, _
                            ByVal dwFlags As Long, _
                            lpMultiByteStr As Any, _
                            ByVal cchMultiByte As Long, _
                            lpWideCharStr As Any, _
                            ByVal cchWideChar As Long) As Long
                           
Sub modStart()
    Dim lngHandle As Long
    Dim mlngDeskTopItemsCount As Long
    Dim nItems As Long
    Dim i As Long
    Dim ptItem As POINTAPI
    Dim strItemName As String
    Dim itmX As ListItem
   
    lngHandle = FindWindow("Progman", vbNullString)
    lngHandle = FindWindowEx(lngHandle, 0, "SHELLDLL_defVIEW", vbNullString)
    lngHandle = FindWindowEx(lngHandle, 0, "SysListView32", "FolderView")

    If lngHandle = 0 Then
        MsgBox "No handle for desktop"
        Exit Sub
    End If
   
    Send.lvwRes.ListItems.Clear
   
    If IsWindow(lngHandle) Then
        mlngDeskTopItemsCount = 0
               
        'Number of desktop items
        nItems = ListView_GetItemCount(lngHandle)
        If nItems = 0 Then
            MsgBox "0 Items found on desktop"
            Exit Sub
        End If
       
        For i = 0 To nItems - 1
           
            strItemName = GetLVItemTextEx(lngHandle, i)
            Set itmX = Send.lvwRes.ListItems.Add(, , strItemName, , 0)
           
            If SendMessageRemote(lngHandle, LVM_GETITEMPOSITION, i, VarPtr(ptItem), Len(ptItem)) Then
                itmX.SubItems(1) = ptItem.X
                itmX.SubItems(2) = ptItem.Y
            Else
                MsgBox "No position found for item " & CStr(i)
            End If
            DoEvents
        Next
    End If

End Sub

Private Function ListView_GetItemCount(hWnd As Long) As Long
On Local Error Resume Next

    ListView_GetItemCount = SendMessage(hWnd, LVM_GETITEMCOUNT, ByVal 0&, ByVal 0&)

End Function

Private Function SendMessageRemote(hWnd As Long, uMsg As Long, wParam As Long, lParam As Long, cbLParam As Long) As Long
On Local Error Resume Next
   
    Dim dwProcessId As Long
    Dim hProcess As Long
    Dim lpMem As Long
    Dim lp As Long
    Dim hFile As Long
 
    If GetWindowThreadProcessId(hWnd, dwProcessId) Then
        hProcess = OpenProcess(PROCESS_VM_OPERATION Or PROCESS_VM_READ Or PROCESS_VM_WRITE, _
                                                 0, dwProcessId)
        If hProcess Then
         
          ' Allocate memory in the remote process's address space
          lpMem = VirtualAllocEx(hProcess, 0, cbLParam, MEM_RESERVE Or MEM_COMMIT, PAGE_READWRITE)
          If lpMem Then
           
            ' Write the local lParam to the remote memory block
            If WriteProcessMemory(hProcess, lpMem, ByVal lParam, cbLParam, lp) = 0 Then
                MsgBox "WriteProcessMemory failed: " & CStr(Err.LastDllError)
            End If
           
            SendMessageRemote = SendMessage(hWnd, uMsg, wParam, ByVal lpMem)
           
            ' Read the remote memory back into lParam
            If ReadProcessMemory(hProcess, lpMem, ByVal lParam, cbLParam, lp) = 0 Then
                MsgBox "ReadProcessmemory failed: " & CStr(Err.LastDllError)
            End If
           
            ' Free the memory in the remote process's address space
            Call VirtualFreeEx(hProcess, lpMem, 0, MEM_RELEASE)
          Else
            MsgBox "lpMem invalid (NULL)"
          End If  ' lpMem
         
          Call CloseHandle(hProcess)
        End If   ' hProcess
       
    End If   ' GetWindowThreadProcessId
 
End Function

Private Function GetLVItemTextEx(hwndLV As Long, iItem As Long) As String
On Local Error Resume Next
 
  Dim lvi As lvItem
  Dim dwProcessId As Long
  Dim abText(CB_MAXLVITEMTEXT) As Byte
  Dim hProcess As Long
  Dim cbMem As Long
  Dim lpMem As Long
  Dim lp As Long
  Dim hFile As Long
 
  ' initialize the local LVITEM struct
  'lvi.mask = LVIF_TEXT
  lvi.iItem = 0
  lvi.iSubItem = 0
  lvi.cchTextMax = CB_MAXLVITEMTEXT
  lvi.iImage = 0
  lvi.iIndent = 0
  lvi.lParam = 0
  lvi.state = 0
  lvi.stateMask = 0
 
  ' get the process ID of hwndLV
  If GetWindowThreadProcessId(hwndLV, dwProcessId) Then

        ' =============================================================================
        ' WinNT, Win2K: read and write memory we allocate in the remote process, see:
        ' http://msdn.microsoft.com/library/periodic/period97/win32qa997.htm
       
        ' open a handle to the remote process
        hProcess = OpenProcess(PROCESS_VM_OPERATION Or PROCESS_VM_READ Or PROCESS_VM_WRITE, _
                                                 0, dwProcessId)
        If hProcess Then
         
          ' Allocate memory in the remote process's address space
          lpMem = VirtualAllocEx(hProcess, 0, Len(lvi), MEM_COMMIT, PAGE_READWRITE)
          If lpMem Then
            ' Allocate space for the result string
            lvi.pszText = VirtualAllocEx(hProcess, 0, CB_MAXLVITEMTEXT, MEM_COMMIT, PAGE_READWRITE)
            If lvi.pszText = 0 Then
                MsgBox "Failed to allocate space for textbuffer " & CStr(Err.LastDllError)
            End If
           
            ' Write the local LVITEM to the remote memory block
            If WriteProcessMemory(hProcess, lpMem, lvi, LenB(lvi), lp) = 0 Then
                MsgBox "WriteProcessmemory failed for CB_LVITEM"
            End If
            Call WriteProcessMemory(hProcess, lvi.pszText, abText(0), CB_MAXLVITEMTEXT, 0)
            
            If SendMessage(hwndLV, LVM_GETITEMTEXT, iItem, ByVal lpMem) > -1 Then
              ' Read the remote text string into our local array buffer and convert it to a VB string
              If ReadProcessMemory(hProcess, lvi.pszText, ByVal VarPtr(abText(0)), CB_MAXLVITEMTEXT, lp) > 0 Then
                 GetLVItemTextEx = GetStrFromPtrA(VarPtr(abText(0)))
              Else
                 MsgBox "ReadProcessmemory failed: " & CStr(Err.LastDllError)
              End If
            Else
              MsgBox "Sendmessage failed: " & CStr(Err.LastDllError)
            End If  ' SendMessage
         
            ' Free the memory in the remote process's address space
            Call VirtualFreeEx(hProcess, lpMem, 0, MEM_RELEASE)
            Call VirtualFreeEx(hProcess, lvi.pszText, 0, MEM_RELEASE)
          Else
            MsgBox "lpMem = NULL"
          End If   ' lpMem
         
          Call CloseHandle(hProcess)
        Else
            MsgBox "OpenProcess Failed (LvItemText)"
        End If   ' hProcess
   
  End If   ' GetWindowThreadProcessId

End Function

Private Function GetStrFromPtrA(lpszA As Long) As String
On Local Error Resume Next
 
  Dim nChars As Long
 
  nChars = lstrlenA(ByVal lpszA)
  If nChars Then
    GetStrFromPtrA = Space$(nChars)
    Call MultiByteToWideChar(CP_ACP, 0, ByVal lpszA, nChars, ByVal StrPtr(GetStrFromPtrA), nChars)
  End If
 
End Function

 

Answer 1

This forum is for VB.NET programming questions only.

 

Please read this about VB6 questions

http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=551512&SiteID=1

Answer 2

Same Problem here, is there already a solution to this?

Answer 3

In the meantime I have find out what the issue is. The problem is that a VB program operates in 32-bit mode, but the explorer in 64 bits mode. Therefore the adresses used by the LVI_GETITEMTEXT call to the explorer must be in 64 bits mode. This can't be done in VB6.

 

I accomplished this by writing the 'kernel'of that program in C++ using the 64-bits SDK from Microsoft. So effectively this is a 64 bits native program performing the LVI_GETITEMTEXT call.

This does the job perfectly.

 

Regards, Ton

Answer 4

I found out what the problem is. VB6 operates in 32 bits mode, but the explorer in 64 bits mode. So the address mappings used in the call to LVI_GETITEMTEXT must be 64 bits, which can't be done in VB6.

 

I solved this by writing the 'kernel'(that is the calls to LVI_GETITEMTEXT and the memory mapings) in VC++ using Microsoft's 64-bit SDK. This works perfectly.

 

Regards,

 

Ton

Answer 5

First of all many thanks for the quick response! Thats indeed an obvious solution but I never thought about the pointer issue I'm using C++ anyway so using a x64 compiler solves that problem as you said Thanks again and have a nice weekend!

Answer 6

Hello Ton Dorland,

I am facing the same problem, I am unable to get text with LVM_GETITEMTEXT on 64-bit machine.  You said "In the meantime I have find out what the issue is. The problem is that a VB program operates in 32-bit mode, but the explorer in 64 bits mode. Therefore the adresses used by the LVI_GETITEMTEXT call to the explorer must be in 64 bits mode. This can't be done in VB6."  What is the solution to this problem for VB.NET?

Regards,
Adjutor

Answer 7

This only applies for .NET but:

I also had LVM_GETITEMTEXT problems.  I got around them by compiling as x86 instead of x64 or "anycpu".