HOWTO: Determine if Windows 95/98 Taskbar Is Visible/Hidden

ID: Q143117

The information in this article applies to:

Microsoft Visual Basic Professional and Enterprise Editions for Windows, versions 5.0, 6.0
Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0

SUMMARY

Both the Windows 95 and Windows 98 taskbar allow you to easily launch Windows application programs and to determine which applications are currently executing. The taskbar can also display status information, such as the current time. This article will explain how you can determine, from within a Visual Basic program, if the taskbar is visible or hidden.

MORE INFORMATION

Windows 95/98 Taskbar

The taskbar in Windows 95 and Windows 98 is an area of the screen that contains icons that let you easily switch from one application to another, launch new applications, or display status information.

You can customize certain aspects of the taskbar. From the Start menu, select Settings/Taskbar. Windows 95 or Windows 98 will display the current settings for the taskbar. For example, if you set the AutoHide option, the taskbar is always hidden from view. To see the taskbar, you simply move the mouse pointer over that area of the screen where the taskbar is located. The taskbar immediately pops into view.

In a Visual Basic program, you can use the SHAppBarMessage function to determine if the taskbar is visible or hidden. To use the SHAppBarMessage function in your program, you must include the following declare statement in the general declarations section of your program:


   Private Declare Function SHAppBarMessage Lib "shell32.dll" (ByVal
   dwMessage As Long, pData As APPBARDATA) As Long

The SHAppBarMessage function requires two arguments. The first argument identifies the appbar message you want to send. The dwMessage argument may be set to one of the following values:


Value                 Description
------------------------------------------------------------------
ABM_ACTIVATE          Notifies the system that an appbar has been
                      activated.

ABM_GETAUTOHIDEBAR    Retrieves the handle of the autohide appbar
                      associated with a particular edge of the screen

ABM_GETSTATE          Retrieves the autohide and always-on-top states of
                      the windows taskbar

ABM_GETTASKBARPOS     Retrieves the bounding rectangle of the Windows
                      taskbar.

ABM_NEW               Registers a new appbar and specifies the message
                      identifier that the system should use to send
                      notification messages to the appbar.

ABM_QUERYPOS          Requests a size and screen position for an appbar
ABM_REMOVE            Unregisters an appbar, removing bar from the
                      system's internal list

ABM_SETAUOTOHIDEBAR   Registers or unregisters an autohide appbar for an
                      edge of the screen

ABM_SETPOS            Sets the size and screen position of an appbar
ABM_WINDOWPOSCHANGED  Notifies the system when an appbar's position has
                      changed

The second argument required by the SHAppBarMessage function is a pointer to an APPBARDATA structure. The actual contents of this structure depends on the message you send to the system. Because you are retrieving the state of the taskbar, you do not need set any of the fields in the APPBARDATA structure. Just set the dwMessage argument to the constant value ABM_GETSTATE to retrieve the current state of the taskbar.

After you call the SHAppBarMessage function, a value is returned indicating the state of the taskbar. If this value is zero, you know the taskbar is not in auto-hide or always-on-top mode. If the value returned is &H1, the taskbar is in auto-hide mode and if the value returned is &H2, the taskbar is in always-on-top mode.

How to Create the Demonstration Program

The demonstration program below shows how to determine if the taskbar in Windows 95 or Windows 98 is visible or hidden.

Create a new project in Visual Basic. Form1 is created by default.

Add the following constant and declare statements to the general declarations section of Form1:


      Private Declare Function SHAppBarMessage Lib "shell32.dll" (ByVal _
      dwMessage As Long, pData As APPBARDATA) As Long
      Const ABS_ALWAYSONTOP = &H2
      Const ABS_AUTOHIDE = &H1
      Const ABM_GETSTATE = &H4

Add a CommandButton control to Form1.

Add the following code to the Click event for Command1:


      Private Sub Command1_Click()
          Dim IsThere As Integer

          IsThere = BarExists()
          If IsThere = 0 Then
              Text1.Text = "TaskBar not in auto-hide or always-on-top mode"
          End If
          If IsThere = ABS_ALWAYSONTOP Then
              Text1.Text = "TaskBar always-on-top"
          End If
          If IsThere = ABS_AUTOHIDE Then
              Text1.Text = "TaskBar in auto-hide"
          End If
      End Sub

Create a new function called BarExists. Add the following code to the General Declarations section of Form1.


      Public Function BarExists() As Integer
          Dim Bardata As APPBARDATA
          BarExists = SHAppBarMessage(ABM_GETSTATE, Bardata)
      End Function

Add a Text Box control to Form1. Set its MultiLine property to True.

Add a new Module to the project.

Add the following Type structures to Module1.Bas:


      Type RECT
              Left As Long
              Top As Long
              Right As Long
              Bottom As Long
      End Type
      Type APPBARDATA
              cbSize As Long
              hwnd As Long
              uCallbackMessage As Long
              uEdge As Long
              rc As RECT
              lParam As Long '  message specific
      End Type

Execute the demonstration program by pressing the F5 key. Click on the Command Button. If the Windows 95 or Windows 98 taskbar is visible on the screen, a message to that effect is displayed in the Text Box. On the other hand, if the taskbar is currently hidden, the Text Box will display the text "Taskbar is auto-hide." If both the Auto-Hide and Always-on-Top properties of the taskbar are not set, then the Text Box will display the message "Taskbar is not in auto-hide or always-on-top mode."

REFERENCES

Product Documentation, SDKs, Win32 SDK, Win32, Reference, Messages. ABM_GETSTATE.

Product Documentation, SDKs, Win32 SDK, Win32, Reference, Structures, ABC to CWPRETSTRUCT. APPBARDATA.

Product Documentation, SDKs, Win32 SDK, Guides, Programmer's Guide to Windows 95.

Additional query words: kbVBp400 kbVBp500 kbVBp kbDSupport kbdsd kbSDKWin32 kbVBp600 KBWIN32SDK KBAPI

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Platform : NT WINDOWS
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