How To Implement "What's This?" Help in ActiveX Control

MORE INFORMATION

An ActiveX control can have its own helpfile and help information for the contained controls. As per encapsulation rules of COM, it is recommended to have separate help system for a UserControl. However, in some cases, it is appropriate to inherit the help from the client form in which the ActiveX control is sited. This article describes both of these methods.

Method 1: Using Separate Help System for the UserControl

If the UserControl has its own helpfile, then this method is well suited.

Step-by-Step Example

1. Start a new ActiveX Control project. UserControl1 is created by default.
2. Place three controls onto the UserControl.
3. Select Project1 Properties from the Project menu. On the General tab, specify the help file in the Help File Name field.
4. For each control on UserControl1, change the WhatsThisHelpId to a valid value for your help file. Close all open windows.
5. Select Add Project from the Project menu to add a new Standard EXE project. Project2 is created by default.
6. Place UserControl1 onto Form1. Change the BorderStyle property of Form1 to Fixed Single. Set the WhatsThisButton property to True.
7. Run the project. Click on the "?" button in the title bar, and then click on any control in the UserControl. The appropriate help is shown.
   
   NOTE: When you click on the "?" button and then click on the UserControl in the area not covered by contained controls, no help is shown. This is because the UserControl does not have a WhatsThisHelpId in design-mode. However, WhatsThisHelpId property is available when it is sited, and the client form can assign a value to it. If you want to assign a WhatThisHelpId at design-time itself, cover the UserControl with a Frame or PictureBox and assign the WhatsThisHelpId to that control.
8. Stop the project. Go to Project Properties of Project2 and specify a helpfile for it.
9. Set the WhatsThisHelpId of UserControl1 to a valid value. Add necessary controls and set their WhatsThisHelpId.
10. Run the project. Click on "?," and then click on the UserControl in the area not covered by contained controls. Note that the correct Help is shown. Note that the help information shown comes from Project2's helpfile and not from UserControl1's helpfile. If this behavior is not desired, apply the "Note" from step 7.

Method 2: Inheriting Help from the Client Application

In some cases, such as when the UserControl is simple, it may not have its own help file. In this case it is desirable to inherit the help system provided by the client application.

Step-by-Step Example

1. Start a new ActiveX Control project. UserControl1 is created by default.
2. Place three controls onto the UserControl.
3. Select Add Project from the Project menu to add a new Standard EXE project. Project2 is created by default.
4. Place UserControl1 onto Form1. Change the BorderStyle property of Form1 to Fixed Single. Set the WhatsThisButton property to True.
5. Select Project2 Properties from the Project menu. On the General tab, specify the help file in the Help File Name field.
6. Set the WhatsThisHelpId of UserControl11 to a valid value. Add necessary controls to Form1 and set their WhatsThisHelpId.
7. Run Project2. Click on "?" and click on UserControl11 in the area not covered by contained controls. The specified help topic is displayed. If any contained control is clicked, no help topic will be displayed. To achieve this effect implement the following steps:
   
   
   1. In the General Declarations section of UserControl1, add the following code:

               Public Property Get HelpFile() As String
                 HelpFile = App.HelpFile
               End Property
      
               Public Property Let HelpFile(ByVal vNewValue As String)
                 If Dir(vNewValue) = "" Then
                     Err.Raise 53  ' File not found
                 Else
                     App.HelpFile = vNewValue
                 End If
               End Property
      
               Public Sub InheritHelp(Optional nWhatsThisHelpId As Integer)
      
                 Dim cTemp As Control
                 If nWhatsThisHelpId = 0 Then
                     nWhatsThisHelpId = UserControl.Extender.WhatsThisHelpID
                 End If
      
                 For Each cTemp In Controls
                     On Error Resume Next  ' Ignore errors in next statement
                     cTemp.WhatsThisHelpID = nWhatsThisHelpId  ' some controls
                                      ' may not have WhatsThisHelpid property
                     On Error GoTo 0  ' Turn off error handling
                 Next
      
               End Sub
         
      								

   2. In the client Form's General Declaration section, add the following code:

               Private Sub Form_Load()
                 UserControl11.HelpFile = App.HelpFile
                 UserControl11.InheritHelp  ' Pass WhatsThisHelpId if different
                       ' help Id is desired for contained controls
                       ' By default, the HelpId of usercontrol will be inherited
               End Sub
         
      								

8. Run the project. Click on "?" and click anywhere on the UserControl. Note that the specified Help Topic is displayed.