How to Hide a VB App from the Task List and ALT+TAB Order

• Microsoft Visual Basic Standard and Professional Editions for Windows, versions 2.0, 3.0

SUMMARY

This article demonstrates how to create an application that is invisible to the Windows Task List and to the fast ALT+TAB switching order.

MORE INFORMATION

All Visual Basic applications have a background window that handles all messages for the application and all calls to the VBRUN300.DLL. This background window is also the owner and parent of all non-MDI child forms. You can use the GetWindow and ShowWindow Windows API functions to hide this background window.

To be eligible for removal from the ALT+TAB order, an application cannot have any visible forms. The background window is visible, but you can use GetWindow to return the background or owner window's handle, and then use the handle and ShowWindow to make the window invisible.

Step-by-Step Example

1. Start a New Project in Visual Basic. Form1 is created by default.



2. Add a timer control (Timer1) to the form.



3. Add the following declarations to the general declarations section:

   
      ' Enter each of the following Declare statements as one, single line:
   
      Declare Function ShowWindow Lib "User" (ByVal hWnd As Integer,
         ByVal nCmdShow As Integer) As Integer
      Declare Function GetWindow Lib "User" (ByVal hWnd As Integer,
         ByVal wCmd As Integer) As Integer
      Const SW_HIDE = 0
      Const GW_OWNER = 4
    




4. Add the following code to the load event of Form1:

   
      Sub Form_Load ()
   
         Dim OwnerhWnd As Integer
         Dim ret As Integer
   
         ' Make sure the form is invisible:
         form1.Visible = False
   
         ' Set interval for timer for 5 seconds, and make sure it is enabled:
         timer1.Interval = 5000
         timer1.Enabled = True
   
         ' Grab the background or owner window:
         OwnerhWnd = GetWindow(Me.hWnd, GW_OWNER)
         ' Hide from task list:
         ret = ShowWindow(OwnerhWnd, SW_HIDE)
   
      End Sub
    




5. Add the following code to the Timer event of the Timer1 control to verify that the program is running and to allow you to exit the program:

   
      Sub Timer1_Timer ()
   
         Dim ret As Integer
   
         ' Display a message box:
       ret = MsgBox("Visible by Alt+Tab. Cancel to Quit", 1, "Invisible Form")
         ' If cancel clicked, end the program:
         If ret = 2 Then
            timer1.Enabled = False
            Unload Me
            End
         End If
   
      End Sub
    




6. Save the project as INVIS.MAK and create an executable entitled INVIS.EXE.



7. Run the program by double-clicking INVIS.EXE in File Manager or by using the Run option in Program Manager. When you run the program, there should be no visible forms and the program title should not appear in the Task List or in the ALT+TAB order. After five seconds, the application should display the message box. Then the program should be visible to the ALT+TAB order, but not the Task List. Click the Cancel button to exit the application, or click OK to allow it to continue to run.

Additional query words: 2.00 3.00 hide invisable

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Last Reviewed: June 2, 1999