DOCUMENT:Q190523  07-AUG-1998  [vbwin]
TITLE   :PRB: Automation Error (-2147417843) Using the System Tray
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:
OPER/SYS:WINDOWS
KEYWORDS:

======================================================================
---------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Visual Basic Learning, Professional, and Enterprise Editions
   for Windows, versions 5.0, 6.0
---------------------------------------------------------------------

SYMPTOMS
========

When using the Shell_NotifyIcon API or the SysTray control sample from the
Visual Basic CD-ROM, you may receive the following error message:

   Run-time error: -2147417843 (8001010d)
   Automation Error

CAUSE
=====

The run-time error occurs because you are trying to make an Automation call
to an out-of-process (ActiveX) EXE from within the event notification of
the system tray callback. The value -2147417843 translates to the following
error message:

   An outgoing call cannot be made since the application is dispatching
   an input-synchronous call.

Automation clients are required by COM to process input-synchronous calls
without interruption, and therefore are prevented from making outgoing
Automation calls while processing such messages.

RESOLUTION
==========

Avoid making outgoing Automation calls during the System Tray callback. If
an Automation method needs to be called in response to a user event
involving the System Tray, use a simple Timer to post yourself a message,
and then let the callback function complete. When the Timer event fires,
you can safely call your Automation method.

STATUS
======

This behavior is by design.

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

Steps to Reproduce Behavior
---------------------------

1. Copy the SysTray control sample from the Tools\Unsupprt directory of the
   Visual Basic 5.0 CD-ROM, or the Common\Tools\VB\Unsupprt directory of
   the Visual Basic 6.0 CD-ROM, to your hard drive.

2. Open the project and compile the control. When complete, close the
   project.

3. Create a new Standard EXE project. Form1 is created by default.

4. From the Project menu, click Components and check "System Tray Icon
   Control". Click OK.

5. Select the SysTray control in the toolbox and add an instance to Form1.

6. Add the following code into Form1's code window:

      Option Explicit
      Private oWord As Object

      Private Sub Form_Load()
         Set oWord = CreateObject("Word.Application")
         Set cSysTray1.TrayIcon = Me.Icon
         cSysTray1.InTray = True
      End Sub

      Private Sub Form_Unload(Cancel As Integer)
         cSysTray1.InTray = False
         Set oWord = Nothing
      End Sub

      Private Sub cSysTray1_MouseDblClick(Button As Integer, Id As Long)
         oWord.Visible = True
      End Sub

7. Run the application by pressing the F5 key. The error will occur when
   you double-click the application's icon in the System Tray. Press END to
   stop the debugger.

8. To avoid the error, add a Timer to Form1.

9. Replace the code in Form1 with the following:

      Option Explicit
      Private oWord As Object

      Private Sub Form_Load()
         Set oWord = CreateObject("Word.Application")
         Set cSysTray1.TrayIcon = Me.Icon
         cSysTray1.InTray = True
         Timer1.Enabled = False
         Timer1.Interval = 10
      End Sub

      Private Sub Form_Unload(Cancel As Integer)
         cSysTray1.InTray = False
         Set oWord = Nothing
      End Sub

      Private Sub cSysTray1_MouseDblClick(Button As Integer, Id As Long)
         Timer1.Enabled = True
      End Sub

      Private Sub Timer1_Timer()
         Timer1.Enabled = False
         oWord.Visible = True
      End Sub

10. Re-run the application by pressing the F5 key. This time no error
   should occur.

REFERENCES
==========

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

   ARTICLE-ID: Q176085
   TITLE     : HOWTO: Use the System Tray Directly from Visual Basic 5.0

Additional query words: kbVBp kbdsd kbDSupport kbVBp500 kbVBp600
kbAutomation
======================================================================
Platform          : WINDOWS
Issue type        : kbprb

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

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