Microsoft KB Archive/185451

= How To Display Descriptions of Menu Items When Highlighted =

Article ID: 185451

Article Last Modified on 3/11/2005

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APPLIES TO


 * Microsoft Visual Basic 6.0 Learning Edition
 * Microsoft Visual Basic 6.0 Professional Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition
 * Microsoft Visual Basic 5.0 Control Creation Edition
 * Microsoft Visual Basic 5.0 Learning Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition

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This article was previously published under Q185451



SUMMARY
Some applications, such as the Windows Explorer, provide a description of each menu item in the status bar when the menu item is highlighted. This functionality provides the user more information about what each menu command does before it is activated.

This article shows you how to use several of the Windows API functions to include this functionality in your Visual Basic application.



MORE INFORMATION
The following steps demonstrate how to create a sample application that provides descriptions for menu items when the menu items are highlighted. To achieve this functionality, you must use a concept known as subclassing to allow you to detect when the WM_MENUSELECT message occurs. This message occurs whenever a menu selection is either highlighted or not highlighted.

For more information on subclassing, please see the following article in the Microsoft Knowledge Base:

168795 How To Hook Into a Window's Messages Using AddressOf

NOTE: Failure to unhook a window before its destruction results in application errors, Invalid Page Faults, or data loss. This occurs because the new WindowProc function that is being pointed to no longer exists, but the window has not been notified of the change. Always unhook the subclassed window upon unloading the subclassed form or exiting the application.

This is especially important when you use Visual Basic to debug an application that includes subclassing. Pressing the End button or selecting End from the Run menu without unhooking causes an Invalid Page Fault and closes Microsoft Visual Basic.

Steps to Create Sample Application
 Create a new Standard EXE project.  Create the following menu on Form1 using the Menu Editor: Menu Caption       Menu Name ---       -

File              mnuFile New             mnuNew Open            mnuOpen Close           mnuClose

Edit              mnuEdit Cut             mnuCut Copy            mnuCopy Paste           mnuPaste Normal       mnuPasteNormal Special      mnuPasteSpecial NOTE: You should create the menu captions exactly as shown. If you choose to add accelerators, you need to modify the following code to reflect these changes to your captions.   Paste the following code into the code window for Form1: Option Explicit

Private Sub Form_Load 'Store a handle to this form. gHW = Me.hwnd

'Call this Sub procedure to begin hooking into messages. Hook End Sub

Private Sub Form_Unload(Cancel As Integer) 'Call this Sub procedure to cease hooking into messages. Unhook End Sub  Add a standard module to the project.  Paste the following code into the module: Option Explicit

Private 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

Private Declare Function SetWindowLong Lib "user32" _ Alias "SetWindowLongA" (ByVal hwnd As Long, _  ByVal nIndex As Long, ByVal dwNewLong As Long) As Long

Private Declare Function GetMenu Lib "user32" _ (ByVal hwnd As Long) As Long

Private Declare Function GetSubMenu Lib "user32" _ (ByVal hMenu As Long, ByVal nPos As Long) As Long

Private Declare Function GetMenuItemCount Lib "user32" _ (ByVal hMenu As Long) As Long

Private Declare Function GetMenuState Lib "user32" _ (ByVal hMenu As Long, ByVal wID As Long, _  ByVal wFlags As Long) As Long

Private Declare Function GetMenuString Lib "user32" _ Alias "GetMenuStringA" (ByVal hMenu As Long, _  ByVal wIDItem As Long, ByVal lpString As String, _   ByVal nMaxCount As Long, ByVal wFlag As Long) As Long

Private Const MF_BYPOSITION = &H400& Private Const MF_HILITE = &H80& Private Const WM_MENUSELECT = &H11F Private Const GWL_WNDPROC = -4

Public lpPrevWndProc As Long Public gHW As Long

Public Sub Hook 'Begin hooking into messages. lpPrevWndProc = SetWindowLong(gHW, GWL_WNDPROC, _   AddressOf WindowProc) End Sub

Public Sub Unhook 'Cease hooking into messages. SetWindowLong gHW, GWL_WNDPROC, lpPrevWndProc End Sub

Function AnyLit(hSubSubMenu As Long) As Long Dim i As Long Dim MenuCount As Long

'Get the number of items in the menu. MenuCount = GetMenuItemCount(hSubSubMenu)

'Loop through the menu items. For i = 0 To MenuCount - 1 'Check whether this item is highlighted. If GetMenuState(hSubSubMenu, i, MF_BYPOSITION) And _ MF_HILITE Then AnyLit = True Exit Function End If   Next i

'Return FALSE, no items highlighted. AnyLit = False End Function

Private Sub WalkSubMenu(hSubMenu As Long) Dim i As Long Dim MenuItems As Long Dim hSubSubMenu As Long Dim buffer As String Dim result As Long

'Get the count of menu items in this menu. MenuItems = GetMenuItemCount(hSubMenu)

'Loop through all the items on the menu. For i = 0 To MenuItems - 1 'Determine whether this item is highlighted. If GetMenuState(hSubMenu, i, MF_BYPOSITION) And _ MF_HILITE Then 'Attempt to get a submenu for each menu item. hSubSubMenu = GetSubMenu(hSubMenu, i)

'Check for a submenu with something selected on it. If hSubSubMenu And AnyLit(hSubSubMenu) Then 'There is a submenu with a selection so walk it. WalkSubMenu hSubSubMenu Else   'This is it. 'Set buffer size. buffer = Space(255)

'Call the API to get the caption for the menu item. result = GetMenuString(hSubMenu, i, buffer, _                  Len(buffer), MF_BYPOSITION)

'Trim the buffer of extra characters. buffer = Left$(buffer, result)

'Set the caption of the form to a description of the 'menu item. Form1.Caption = GetDescription(buffer)

'Exit this Sub procedure. Exit Sub End If       End If    Next i End Sub

Public Sub FindHilite(TheForm As Form) Dim hMenu As Long Dim hSubMenu As Long Dim i As Long Dim MenuCount As Long

'Clear any previous description. Form1.Caption = ""

'Get the menu handle. hMenu = GetMenu(TheForm.hwnd)

'Check to see if there is no menu. If hMenu <> 0 Then 'Get the number of top-level menus. MenuCount = GetMenuItemCount(hMenu)

'Enumerate through all top-level menus. For i = 0 To MenuCount - 1 'Ignore top-level menus not currently selected. If GetMenuState(hMenu, i, MF_BYPOSITION) And _ MF_HILITE Then 'Get a handle to the submenu. hSubMenu = GetSubMenu(hMenu, i)

'Walk the submenu. WalkSubMenu hSubMenu End If       Next i    End If End Sub

Private Function GetDescription(MenuCaption As String) As String 'Determine the description of the menu item. Select Case MenuCaption Case "New" GetDescription = "Creates a new document" Case "Open" GetDescription = "Opens a Document" Case "Close" GetDescription = "Closes Document" Case "Cut" GetDescription = "Cuts Selection to Clipboard" Case "Copy" GetDescription = "Copies Selection to Clipboard" Case "Paste" GetDescription = "Pastes Contents of Clipboard" Case "Normal" GetDescription = "Regular Paste" Case "Special" GetDescription = "Special Paste" Case Else GetDescription = "" End Select End Function

Function WindowProc(ByVal hw As Long, ByVal uMsg As Long, _      ByVal wParam As Long, ByVal lParam As Long) As Long

'Check for a menu selection message. If uMsg = WM_MENUSELECT Then FindHilite Form1 End If

'Pass the message to Windows for processing. WindowProc = CallWindowProc(lpPrevWndProc, hw, uMsg, _      wParam, lParam) End Function  Click Start or click the F5 key to start the program. Open various menu items and observe the changes that occur to the form's caption.</li></ol>

Additional query words: Hook Subclass

Keywords: kbhowto kbmenu kbapi KB185451

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