BUG: Hide Event Doesn't Fire Correctly in Internet Explorer 4.0

• 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.