Q143117: HOWTO: Determine if Windows 95/98/Me Taskbar Is Visible/Hidden
Article: Q143117
Product(s): Microsoft Visual Basic for Windows
Version(s): 4.0,5.0,6.0
Operating System(s):
Keyword(s): kbAPI kbSDKWin32 kbVBp kbVBp400 kbVBp500 kbVBp600 kbGrpDSVB kbDSupport
Last Modified: 28-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0
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SUMMARY
=======
The Windows 95, Windows 98, Windows Me, Windows NT 4.0, and Windows 2000 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/Me Taskbar
------------------------
The taskbar in Windows 95, Windows 98, Windows Me, Windows NT 4.0, and Windows
2000 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 and Start menu. Windows 95, Windows 98, Windows Me, Windows NT
4.0, or Windows 2000 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 to 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. If the value returned is &H2, the taskbar is in
always-on-top mode. If the value returned is &H3, the taskbar is both in
auto-hide mode and always-on-top.
How to Create the Demonstration Program
---------------------------------------
The demonstration program below shows how to determine if the taskbar in Windows
95, Windows 98, Windows Me, Windows NT 4.0, or Windows 2000 is visible or
hidden.
1. Create a new project in Visual Basic. Form1 is created by default.
2. 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 ABS_BOTH = &H3
Const ABM_GETSTATE = &H4
3. Add a CommandButton control to Form1.
4. 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
If IsThere = ABS_BOTH Then
Text1.Text = "TaskBar is always-on-top and auto-hide"
End If
End Sub
5. 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
6. Add a Text Box control to Form1. Set its MultiLine property to True.
7. Add a new Module to the project.
8. 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, Windows 98, Windows Me, Windows NT 4.0 or Windows
2000 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 set, then the Text Box will display
the message "TaskBar is always-on-top and auto-hide." If neither the Auto-Hide
and Always-on-Top properties of the taskbar are 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:
======================================================================
Keywords : kbAPI kbSDKWin32 kbVBp kbVBp400 kbVBp500 kbVBp600 kbGrpDSVB kbDSupport
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400
Version : :4.0,5.0,6.0
Issue type : kbhowto
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