DOCUMENT:Q177674  05-DEC-1997  [vbwin]
TITLE   :HOWTO: Toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK Keys
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:WINDOWS:4.0,5.0
OPER/SYS:WINDOWS
KEYWORDS:vb432 VB4WIN vb5all vb5howto

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The information in this article applies to:

 - Microsoft Visual Basic Learning, Professional, and Enterprise Editions
   for Windows, version 5.0
 - Microsoft Visual Basic Standard, Professional, and Enterprise Editions,
   32-bit only, for Windows, version 4.0
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SUMMARY
=======

This article demonstrates how to toggle the NUM LOCK, CAPS LOCK, AND SCROLL
LOCK keys under both Windows 95 and Windows NT.

MORE INFORMATION
================

To toggle the NUM LOCK, CAPS LOCK, or SCROLL LOCK keys, you can use the
following logic:

- Use the GetKeyboardState function to determine the state of the key.

- Determine which operating system is being used with the GetVersionEx API.
  (Windows 95 and Windows NT require different methods for toggling these
  keys.)

- Under Windows 95, use the SetKeyboardState API function to set the state
  of the key. Under Windows NT, use the keybd_event function to simulate a
  key press.

This example shows how to toggle these three keys to "on" if they are
"off." This sample may be easily modified to toggle them off or just to
check their state.

Sample Project
--------------

1. Start a new Standard EXE project in Visual Basic. Form1 is created by
   default.

2. Add a CommandButton to Form1.

3. Add the following code to the General Declarations section of Form1:

      ' Declare Type for API call:
      Private Type OSVERSIONINFO
        dwOSVersionInfoSize As Long
        dwMajorVersion As Long
        dwMinorVersion As Long
        dwBuildNumber As Long
        dwPlatformId As Long
        szCSDVersion As String * 128   '  Maintenance string for PSS usage
      End Type

      ' API declarations:
      Private Declare Function GetVersionEx Lib "kernel32" _
         Alias "GetVersionExA" _
         (lpVersionInformation As OSVERSIONINFO) As Long

      Private Declare Sub keybd_event Lib "user32" _
         (ByVal bVk As Byte, _
          ByVal bScan As Byte, _
          ByVal dwFlags As Long, ByVal dwExtraInfo As Long)

      Private Declare Function GetKeyboardState Lib "user32" _
         (pbKeyState As Byte) As Long

      Private Declare Function SetKeyboardState Lib "user32" _
         (lppbKeyState As Byte) As Long

      ' Constant declarations:
      Const VK_NUMLOCK = &H90
      Const VK_SCROLL = &H91
      Const VK_CAPITAL = &H14
      Const KEYEVENTF_EXTENDEDKEY = &H1
      Const KEYEVENTF_KEYUP = &H2
      Const VER_PLATFORM_WIN32_NT = 2
      Const VER_PLATFORM_WIN32_WINDOWS = 1

4. Add the following code to the Click event of the CommandButton:

      Private Sub Command1_Click()
        Dim o As OSVERSIONINFO
        Dim NumLockState As Boolean
        Dim ScrollLockState As Boolean
        Dim CapsLockState As Boolean

        o.dwOSVersionInfoSize = Len(o)
        GetVersionEx o
        Dim keys(0 To 255) As Byte
        GetKeyboardState keys(0)

        ' NumLock handling:
        NumLockState = keys(VK_NUMLOCK)
        If NumLockState <> True Then    'Turn numlock on
          If o.dwPlatformId = VER_PLATFORM_WIN32_WINDOWS Then  '===== Win95
            keys(VK_NUMLOCK) = 1
            SetKeyboardState keys(0)
          ElseIf o.dwPlatformId = VER_PLATFORM_WIN32_NT Then   '===== WinNT
          'Simulate Key Press
            keybd_event VK_NUMLOCK, &H45, KEYEVENTF_EXTENDEDKEY Or 0, 0
          'Simulate Key Release
            keybd_event VK_NUMLOCK, &H45, KEYEVENTF_EXTENDEDKEY _
               Or KEYEVENTF_KEYUP, 0
          End If
        End If

        ' CapsLock handling:
        CapsLockState = keys(VK_CAPITAL)
        If CapsLockState <> True Then    'Turn capslock on
          If o.dwPlatformId = VER_PLATFORM_WIN32_WINDOWS Then  '===== Win95
            keys(VK_CAPITAL) = 1
            SetKeyboardState keys(0)
          ElseIf o.dwPlatformId = VER_PLATFORM_WIN32_NT Then   '===== WinNT
          'Simulate Key Press
            keybd_event VK_CAPITAL, &H45, KEYEVENTF_EXTENDEDKEY Or 0, 0
          'Simulate Key Release
            keybd_event VK_CAPITAL, &H45, KEYEVENTF_EXTENDEDKEY _
               Or KEYEVENTF_KEYUP, 0
          End If
        End If

        ' ScrollLock handling:
        ScrollLockState = keys(VK_SCROLL)
        If ScrollLockState <> True Then    'Turn Scroll lock on
          If o.dwPlatformId = VER_PLATFORM_WIN32_WINDOWS Then  '===== Win95
            keys(VK_SCROLL) = 1
            SetKeyboardState keys(0)
          ElseIf o.dwPlatformId = VER_PLATFORM_WIN32_NT Then   '===== WinNT
          'Simulate Key Press
            keybd_event VK_SCROLL, &H45, KEYEVENTF_EXTENDEDKEY Or 0, 0
          'Simulate Key Release
            keybd_event VK_SCROLL, &H45, KEYEVENTF_EXTENDEDKEY _
              Or KEYEVENTF_KEYUP, 0
          End If
        End If
      End Sub

5. Press the F5 key to run the program. Click the CommandButton. The state
   of the CAPS LOCK, the NUM LOCK, and the SCROLL LOCK keys should all be
   "on."

REFERENCES
==========

For additional information, please see the following articles in the
Microsoft Knowledge Base:

   ARTICLE-ID: Q127190
   TITLE     : HOWTO: Toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK Keys

Additional query words: numlock capslock scrolllock key state
======================================================================
Keywords          : vb432 VB4WIN vb5all vb5howto
Version           : WINDOWS:4.0,5.0
Platform          : WINDOWS
Issue type        : kbhowto

=============================================================================

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Copyright Microsoft Corporation 1997.