[vba] Ways for improvement of MS Office window subclassing

Hi,

I know this is a bad idea to subclass Word / Excel windows (because many reasons, at least these), but anyway I want to have such one (e.g. for RegisterHotkey to have an opportunity to redefine some internal hotkeys to obtain a more convenient tools for editing text).

Enough words. I rewrote a little bit a code based on Jaafar Tribak source.
My edits related to simplify code. Also I added safe UnSubclass with help of 'The Trick'. But I don't very familiar with subclassing in general.

For people, who worked with subclassing (like fafalone project) and still intrested,
what do you think, how can we improve this code to be more safely?

For now, it's for MS Excel only:
Thisworkbook

Code:

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Option Explicit

Private Sub Workbook_BeforeClose(Cancel As Boolean)
    'unsubclass the window.
    'flag = False
    Call UnSubClassExcel(Application.hWnd)
End Sub

Private Sub Workbook_Open()
    'let's subclass the main
    'excel application window.
    Call Safe_Subclass(Application.hWnd)
End Sub


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Module1.bas

Code:

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'Forked by Alex Dragokas
'Thanks for safe UnSubclassing example goes to 'The Trick'.

'Copyrights:
'MS Excel Subclassing by Jaafar Tribak - http://www.mrexcel.com/forum/general-excel-discussion-other-questions/420673-challenging-problem-how-make-excel-subclassing-safe-stable.html#post2082195

Option Explicit

Private Declare Function SetWindowLong Lib "user32.dll" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function CallWindowProc Lib "user32.dll" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal MSG As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function ShowWindow Lib "user32.dll" (ByVal hWnd As Long, ByVal nCmdShow As Long) As Long
Private Declare Function PostMessage Lib "user32.dll" Alias "PostMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Declare Function RegisterHotKey Lib "user32.dll" (ByVal hWnd As Long, ByVal id As Long, ByVal fsModifiers As Long, ByVal vk As Long) As Long
Private Declare Function UnregisterHotKey Lib "user32.dll" (ByVal hWnd As Long, ByVal id As Long) As Long

Private Const GWL_WNDPROC As Long = -4&
Private Const WM_USER As Long = &H400&
'Classes
Private Const VBE_CLASS_NAME As String = "wndclass_desked_gsk"
'UnSubclassing
Private Const WM_SYSCOMMAND As Long = &H112&
Private Const SC_CLOSE As Long = &HF060&

Dim lOldWinProc As Long
Dim lVBEhwnd As Long


Sub Safe_Subclass(hWnd As Long)

    Static IsSubclassed As Boolean

    'don't subclass the window twice !
    If IsSubclassed Then
        Exit Sub
    Else
        IsSubclassed = True
    End If

    'retrieve the VBE hwnd.
    lVBEhwnd = FindWindow(VBE_CLASS_NAME, vbNullString)

    'stop and reset the VBE first to safely proceed with our subclassing
    PostMessage lVBEhwnd, ByVal WM_USER + &HC44&, ByVal &H30&, ByVal 0&
    PostMessage lVBEhwnd, ByVal WM_USER + &HC44&, ByVal &H33&, ByVal 0&
    PostMessage lVBEhwnd, ByVal WM_USER + &HC44&, ByVal &H83&, ByVal 0&

    'run a one time timer and subclass owr app
    'from the timer callback function.
    'if subclassing is not installed within
    'the timer callback, app. will crash !
    Application.OnTime Now + TimeValue("00:00:01"), "TimerProc"

End Sub

Sub UnSubClassExcel(hWnd As Long)
    'remove the subclass and cleanup.
    SetWindowLong hWnd, GWL_WNDPROC, lOldWinProc
    lOldWinProc = 0
    Release
End Sub

Public Sub TimerProc()
    'hide the VBE.
    ShowWindow lVBEhwnd, 0&

    'and at last we can now safely subclass our target window.
    lOldWinProc = SetWindowLong(Application.hWnd, GWL_WNDPROC, AddressOf WindowProc)

    RegHotKey
End Sub

Private Function WindowProc(ByVal hWnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

    Const WM_HOTKEY As Long = &H312&

    Select Case uMsg
        Case WM_SYSCOMMAND
            If wParam = SC_CLOSE Then
                Release
                WindowProc = 0
                Call UnSubClassExcel(Application.hWnd)
                PostMessage hWnd, WM_SYSCOMMAND, SC_CLOSE, lParam
            End If
        Case WM_HOTKEY
            If wParam = 1 Then
                Debug.Print "Key is pressed: " & wParam
            End If
  End Select
  WindowProc = CallWindowProc(lOldWinProc, hWnd, uMsg, wParam, lParam)
End Function

Sub RegHotKey()
    Const MOD_CONTROL As Long = 2&
    Const MOD_SHIFT As Long = 4&
    Const MOD_ALT As Long = 1&
    Const VK_RETURN As Long = &HD&
    Const VK_NUMPAD0 As Long = &H60&

    Dim lret&

    lret = RegisterHotKey(Application.hWnd, 1, MOD_SHIFT, VK_RETURN)

    Debug.Print "RegisterHotKey = " & lret
End Sub

Sub Release()
    UnregisterHotKey Application.hWnd, 1
End Sub


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To use, click Ctrl + Shift + Enter, and you'll get a msg in immediate window.

Thanks in advance,
Alex.

I've been playing with subclassing in Excel for the past few months. With a bit of machine code you can achieve quite save subclassing that can handle project resets and stuff like that.
Unfortunately it works only in version 2007 and below. In 2010+ it doesn't work at all, and I'm still trying to figure out why.

Here is very, very simple ASM code that in my opinion should not crash excel immediately but it does (in version 2010 and above)

Code:

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format binary
include 'macro/proc32.inc'
_patch1_        = 01BCCAABh    ;  previous WndProc
_patch2_        = 02BCCAABh    ; CallWindowProc

call WndProc

use32
proc WndProc hWnd:DWORD, uMsg:DWORD, wParam:DWORD, lParam:DWORD
_init:
    push    [lParam]
    push    [wParam]
    push    [uMsg]
    push    [hWnd]
    push    dword _patch1_
    call    dword _patch2_
    ret
endp

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What if create much complicated thing.
To subclass not VBE window, but create own hidden window and provide pointer to WindowProc function inside dynamically created shellcode, that will transmit data to main app. using pipes and calling user defined event, so, VBE will know when to receive next piece of data from the pipe.