DOCUMENT:Q175907  29-OCT-1997  [vbwin]
TITLE   :BUG: Hide Event Doesn't Fire Correctly in Internet Explorer 4.0
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:WINDOWS:4.0,5.0
OPER/SYS:WINDOWS
KEYWORDS:vb5all

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

 - Microsoft Visual Basic Control Creation, Professional, and Enterprise
   Editions for Windows, version 5.0
 - Microsoft Internet Explorer (Programming), version 4.0
---------------------------------------------------------------------

SYMPTOMS
========

Code placed in the Hide event of a UserDocument or a UserControl does not
execute under Internet Explorer 4.0. The Hide event does not fire correctly
for the following:

 - ActiveX DLL UserDocument with Apartment-threading

 - ActiveX DLL UserDocument with Single-threading and absence of Active
   Desktop

 - ActiveX Control OCX with Apartment-threading

 - ActiveX Control OCX with Single-threading and absence of Active
   Desktop

CAUSE
=====

The Hide event is not getting fired for UserControl and UserDocument
objects because these objects are being released before receiving the Hide
event. Internet Explorer 3.0 does not have this problem because it
maintains a four-page cache. Internet Explorer 4.0 does not have a four-
page cache.

RESOLUTION
==========

Resolution for UserDocuments
----------------------------

Make your project an ActiveX EXE. Out-of-process (EXE) projects do not have
this problem. Following are the steps to convert an existing ActiveX DLL
project into an ActiveX EXE project:

1. Unregister the ActiveX DLL from your development machine. Use the
   REGSVR32.EXE utility with /U parameter. For example, to unregister an
   DLL called MYPROJ.DLL, navigate to the directory where the DLL is loaded
   and type REGSVR32 /U MYPROJ.DLL.

2. Rename the ActiveX DLL. Use another file name that will only be used for
   providing Binary compatibility. For example, Comp_OLDNAME.DLL where
   OLDNAME is the name of your original DLL.

3. From the Project properties General Tab, change Project Type from
   ActiveX DLL to ActiveX EXE.

4. From the Project properties Component Tab, specify Binary Compatibility
   on the Comp_OLDNAME.DLL

5. Compile your project to create an ActiveX EXE.

Resolution for UserControls
---------------------------

Make your project Single-threaded and make sure that Internet Explorer 4.0
Active Desktop is enabled on machines where your control is going to be
used.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed
at the beginning of this article. We are researching this bug and will post
new information here in the Microsoft Knowledge Base as it becomes
available.

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

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

1. Create a new ActiveX DLL project.

2. From the Project properties, General, change threading model to be
   "Apartment Threaded."

3. Create a procedure to write debug messages to a file in your project
   directory. Cut and paste the following code into your userdocument:

      Sub OutputDebug(iStr As String)
          Dim H As Integer

          H = FreeFile
          Open App.Path + "\" + App.EXEName + "_Debug.TXT" For Append As #H
          Print #H, iStr
          Close #H
      End Sub

4. Add the following code to the Show and Hide events of your UserDocument:

      Private Sub UserDocument_Hide()
          OutputDebug "UserDocument_Hide"
      End Sub

      Private Sub UserDocument_Show()
          OutputDebug "UserDocument_Show"
      End Sub

5. Save your project.

6. Compile the ActiveX DLL. Go into the Project Properties, Component and
   set Binary Compatibility to your ActiveX DLL.

7. Save your project again.

8. From Internet Explorer 4.0, navigate to .VBD file for your project. Wait
   for your userdocument to display.

9. From Internet Explorer 4.0, navigate to a new location such as
   www.microsoft.com.

10. Exit Internet Explorer 4.0.

11. Examine the PROJNAME_debug.txt file in your project directory. Note
   that there is no Hide event message in the file. This indicates that the
   Hide event was never fired.

Additional query words: VBD Hide OCX
======================================================================
Keywords          : vb5all
Technology        : kbInetDev
Version           : WINDOWS:4.0,5.0
Platform          : WINDOWS
Issue type        : kbbug

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

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Copyright Microsoft Corporation 1997.