Subclassing Needed??

[WadeD]

Hi, I want to take a menu that's presented on a main window, and bring it down into its child windows. I know how to capture and insert menus. Would I then have to subclass the child windows and then pass that to the menus that reside on the parent window? If I subclass, would I be responsible for passing every message or could I just subclass the menu? Or is there a better way not involving subclassing?

This is all new to me, so I could be way off on the strategy. Any help's greatly appreciated.

Thanks,
Wade

[WadeD]

Ok, after I append menus to a child window, I then test for those IDs in my callback procedure to call the corresponding menu item in the parent window.

Can I assign different IDs to each menu within a child, but use the same constants across the set of child windows? For example, Change Business Date may be given an ID of 1008 and Close may be given an ID of 1034. In every child window, could I always use the 1008 for Change Business Date and 1034 for Close and then test for this constant (and the active window) in my callback procedure??

Thanks in advance,
Wade

[Aaron Young]

I'm not quite sure why you'd want to replicate the MDIForms Menu on Child Forms, but here's how you can do it:

You can't add a Menu to an MDI Child, so you'll have to use Standard Forms, if you want to, then there's an extra line I've remarked out in the Code, that will use the SetParent API to make the Normal Form a Child of the MDIForm, (not a True Child, but as good as it gets):

Add a Standard Module..

'---[Duplicate Menu]---
'Written by Aaron Young, March 9th 2000
'
Public Type MENUITEMINFO
    cbSize As Long
    fMask As Long
    fType As Long
    fState As Long
    wID As Long
    hSubMenu As Long
    hbmpChecked As Long
    hbmpUnchecked As Long
    dwItemData As Long
    dwTypeData As String
    cch As Long
End Type

'---[Menu API's]---
Public Declare Function GetMenu Lib "user32" (ByVal Hwnd As Long) As Long
Public Declare Function SetMenu Lib "user32" (ByVal Hwnd As Long, ByVal hMenu As Long) As Long
Public Declare Function GetMenuItemInfo Lib "user32" Alias "GetMenuItemInfoA" (ByVal hMenu As Long, ByVal un As Long, ByVal b As Long, lpMenuItemInfo As MENUITEMINFO) As Long
Public Declare Function CreateMenu Lib "user32" () As Long
Public Declare Function InsertMenuItem Lib "user32" Alias "InsertMenuItemA" (ByVal hMenu As Long, ByVal un As Long, ByVal bool As Boolean, ByRef lpcMenuItemInfo As MENUITEMINFO) As Long
Public Declare Function GetMenuItemCount Lib "user32" (ByVal hMenu As Long) As Long

'---[Window & Messaging API's]---
Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal Hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Public Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal Hwnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal Hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Public Declare Function SetParent Lib "user32" (ByVal hWndChild As Long, ByVal hWndNewParent As Long) As Long
Public Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long

'---[API Constants]---
Public Const GWL_WNDPROC = (-4)
Public Const WM_QUIT = &H12
Public Const WM_CLOSE = &H10
Public Const WM_DESTROY = &H2
Public Const WM_COMMAND = &H111

Public Const MIIM_STATE = &H1
Public Const MIIM_ID = &H2
Public Const MIIM_SUBMENU = &H4
Public Const MIIM_CHECKMARKS = &H8
Public Const MIIM_TYPE = &H10
Public Const MIIM_DATA = &H20
Public Const MIIM_ALL = MIIM_STATE Or MIIM_ID Or MIIM_SUBMENU Or MIIM_CHECKMARKS Or MIIM_TYPE Or MIIM_DATA

Public Const MFT_STRING = &H0&

'---[UDT - Used to Store Subclassing Info for Multiple Forms]---
Private Type PrevFunc
    Hwnd As Long
    PrevWndFunc As Long
End Type

Private lHwndFunc() As PrevFunc
Private iFuncs As Long

'--[Source Window Handle, (MDIForm)]---
Public lSrcHwnd As Long

Public Sub SubClassForm(ByVal Hwnd As Long)
    'Subclass the Form
    ReDim Preserve lHwndFunc(iFuncs)
    lHwndFunc(iFuncs).Hwnd = Hwnd
    lHwndFunc(iFuncs).PrevWndFunc = SetWindowLong(Hwnd, GWL_WNDPROC, AddressOf WindowProc)
    iFuncs = iFuncs + 1
End Sub

Private Function WindowProc(ByVal Hwnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    '---[WindowProc Callback Function used by ALL Subclassed Windows]---
    Dim lPrevFunc As Long
    'Get the Original WindowProc Address for this Window
    lPrevFunc = GetPrevFunc(Hwnd)
    Select Case Msg
    Case WM_COMMAND
        'Send the Menu Selection to the Source Window, (MDIForm)
        Call SendMessage(lSrcHwnd, Msg, wParam, ByVal lParam)
    Case WM_CLOSE, WM_QUIT, WM_DESTROY
        'Automatically Remove Window Subclassing when the Window is unloaded
        Call SetWindowLong(Hwnd, GWL_WNDPROC, lPrevFunc)
        Call RemoveFunc(Hwnd)
    End Select
    'Pass Messages to Original Window Proc
    WindowProc = CallWindowProc(lPrevFunc, Hwnd, Msg, wParam, lParam)
End Function

Private Function GetPrevFunc(ByVal Hwnd As Long) As Long
    'Function to find the Previous Window Proc of a Specified Window Handle
    Dim iIndex As Long
    For iIndex = 0 To UBound(lHwndFunc)
        If lHwndFunc(iIndex).Hwnd = Hwnd Then Exit For
    Next
    GetPrevFunc = lHwndFunc(iIndex).PrevWndFunc
End Function

Private Sub RemoveFunc(ByVal Hwnd As Long)
    'Sub to Tidy up the Array of Subclassing Info after Removing an Element
    Dim iIndex As Long
    Dim iNewIndex As Long
    For iIndex = 0 To UBound(lHwndFunc)
        If lHwndFunc(iIndex).Hwnd <> Hwnd Then
            With lHwndFunc(iNewIndex)
                .Hwnd = lHwndFunc(iIndex).Hwnd
                .PrevWndFunc = lHwndFunc(iIndex).PrevWndFunc
                iNewIndex = iNewIndex + 1
            End With
        End If
    Next
    If iNewIndex Then ReDim Preserve lHwndFunc(iNewIndex - 1)
    iFuncs = iNewIndex
End Sub

Add a Class Module and Name it Subclass..

'---[Class Module: Subclass]---
Private lDestMenu As Long

Public Function DuplicateMenu(ByVal SrcHwnd As Long, ByVal DestHwnd As Long) As Boolean
    '---[Enumerate all Items in the Source windows Menu and Duplicate it]---
    Dim lSrcMenu As Long
    lSrcHwnd = SrcHwnd
    lSrcMenu = GetMenu(SrcHwnd)
    If lSrcMenu Then
        lDestMenu = CreateMenu
        EnumerateMenuItems lSrcMenu, lDestMenu
        'Assign the Duplicate Menu to the Destination Window
        Call SetMenu(DestHwnd, lDestMenu)
        'Subclass the Window to Capture the Menu Messages
        Call SubClassForm(DestHwnd)
        'Include this next line to make the Form a Child of the MDI Client
        'Call SetParent(DestHwnd, FindWindowEx(SrcHwnd, 0, "MDIClient", vbNullString))
        DuplicateMenu = True
    End If
End Function

Private Sub EnumerateMenuItems(ByVal lMainMenu As Long, ByVal DstMenu As Long, Optional ByVal Level As Long)
    '---[Recursive Sub Enumerates a Menu's Items at ALL Levels]---
    Dim iItems As Long
    Dim iItem As Long
    Dim tMENUITEMINFO As MENUITEMINFO
    Dim lSubMenu As Long
    
    'Get the Number of Items in this Menu/Submenu
    iItems = GetMenuItemCount(lMainMenu)
    For iItem = 0 To iItems - 1
        'Prepare the UTD to Retrieve all Menu Item Info
        With tMENUITEMINFO
            .fMask = MIIM_ALL
            .fType = MFT_STRING
            .dwTypeData = Space(256)
            .cch = 256
            .cbSize = Len(tMENUITEMINFO)
        End With
        Call GetMenuItemInfo(lMainMenu, iItem, True, tMENUITEMINFO)
        With tMENUITEMINFO
            If .hSubMenu Then
                'Menu Item has a SubMenu
                'Replicate and Enumerate it
                lSubMenu = CreateMenu
                EnumerateMenuItems .hSubMenu, lSubMenu, Level + 1
                .hSubMenu = lSubMenu
            End If
            'Add this Menu Item to the Duplicate Copy
            Call InsertMenuItem(DstMenu, iItem, True, tMENUITEMINFO)
        End With
    Next
End Sub

Public Sub ReDrawMenu(ByVal Hwnd As Long)
    'The Menu needs to be reassign and redrawn when
    'the Window Gets/Loses Focus
    Call SetMenu(Hwnd, lDestMenu)
End Sub

In Each Form that is to Duplicate the MDIForms Menu..

Private DupMenu As New Subclass

Private Sub Form_Activate()
    Static bSet As Boolean
    If Not bSet Then bSet = DupMenu.DuplicateMenu(MDIForm1.Hwnd, Hwnd)
    DupMenu.ReDrawMenu Hwnd
End Sub

[WadeD]

Aaron,

The reason I'm bringing the parent menu down into child windows is because I'm working
with an external accounting app that has dozens of windows in each module and the windows
do not stay within a central container, so users could become confused.

Can this work for an external app?

Thanks,
Wade

[Aaron Young]

Yes, this can work for an External Application, as you're not Subclassing the External App, you're Subclassing your Own Form(s) and Forwarding Messages to the External App.

Just Replace MDIForm.hwnd with the Window Handle of the External Application.

I've tried it and it does work.

[WadeD]

Thanks for the awesome code, Aaron. But both the parent and child windows are external
apps. If I make the destination window an external app, the menu copies over, but doesn't send
its messages to the parent. I want the child to have the parent's menu and my app to be the go-
between that detects the user's menu selection and sends it to the parent.

Can I use LoadLibraryEx to map the child into the same process as my app or
AttachThreadInput to attach the threads? Then the child could have the menu, but I could
subclass it so that my app could read its messages.

Thanks,
Wade

Edited by WadeD on 03-13-2000 at 02:45 PM

[Aaron Young]

I'm afraid not, now you're talking about subclassing
something that doesn't belong to your thread,
which you can only do going through a Windows DLL which you can't create with VB.

Here's an idea that just forced its way to the surface of
my dried up little grey cells..

What if you made the Child App's Window a Child of your own
Applications Main Form, then Add the Parent Apps Menu to your Form, this would at least group the Parent Apps Menu
with the Child App on the Same Form and the subclassing
principle would be the same as that demonstrated in my example.

You should just need to locate the Window Handle on the 3rd
Party Child App and use the SetParent API to put it
inside your own Form or a Picturebox on your own Form.

Otherwise dust off that C++ Manual and enjoy

[WadeD]

Thanks for all the help. 2 questions. If I don't pass the message in WindowProc, it locks up. Do I
have to pass every message?

The menu seems to be deleted every time the window loses focus. So if the user clicks on the
picture box (containing the external child app) and then the window, they see a menu disappear
and reappear each time. Is there a way to keep the menu from being deleted?

Thanks again,
Wade

Edited by WadeD on 03-15-2000 at 11:03 AM