Q185451: HOWTO: Display Descriptions of Menu Items When Highlighted
Article: Q185451
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0
Operating System(s):
Keyword(s): kbAPI kbMenu kbVBp500 kbVBp600 kbOSWin32s
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, version 6.0
- Microsoft Visual Basic Professional Edition for Windows, version 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0
- Microsoft Visual Basic Control Creation Edition for Windows, version 5.0
- Microsoft Visual Basic Learning Edition for Windows, version 5.0
- Microsoft Visual Basic Professional Edition for Windows, version 5.0
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0
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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:
Q168795 HOWTO: 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
----------------------------------
1. Create a new Standard EXE project.
2. 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.
3. 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
4. Add a standard module to the project.
5. 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
6. 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.
Additional query words: Hook Subclass
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Keywords : kbAPI kbMenu kbVBp500 kbVBp600 kbOSWin32s
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbZNotKeyword3
Version : WINDOWS:5.0,6.0
Issue type : kbhowto
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