* VB-CODE (1)
Tip 67: Returning Focus to a Specific Control After Executing WinHelp
Created: April 24, 1995
You can add online Help to your Visual Basic® application by using the
Windows® application programming interface (API) WinHelp function.
However, you need to keep the focus on the control that had the focus
just before you executed the WinHelp function. This article explains
how a control can retain the focus after calling WinHelp.
Using Form-Level Variables to Retain Focus
Almost every application developed for Windows® includes a Help
command. In a Visual Basic® application, you can attach a Help command
to a Command Button control. When the user clicks on the Command
Button, your program calls the Windows application programming
interface (API) WinHelp function to display the actual Help file.
After the user exits the Help program, however, the Command Button
control now has the focus. It would be preferable to have the focus
set to the control (such as a Text Box control) that had the focus
before WinHelp was executed.
You can force your application to automatically retain a control's
focus by defining a Form-level variable as a control. When the focus
is moved to a different control, such as a Text Box, the Form-level
variable should be set to the control that is getting the focus. Then,
after displaying the Help file, the focus can be set back to the
control by using the Form-level variable.
In the example program below, the focus returns to the Text Box
control each time the Help Command Button is clicked. In other words,
the Command Button never retains the focus.
1. Create a new project in Visual Basic. Form1 is created by default.
2. Add the following statements to the General Declarations section
of Form1 (note that the Declare statement should be typed as a
single line of code):
Const HELP_CONTENTS = &H3
Declare Function WinHelp Lib "User" (ByVal hWnd As Integer,
ByVal lpHelpFile As String, ByVal wCommand As Integer,
dwData As Any) As Integer
Dim ControlWithFocus As Control
3. Add a Text Box control to Form1. Text1 is created by default.
4. Add the following code to the GotFocus event for Text1:
Set ControlWithFocus = Text1
5. Add a second Text Box control to Form1. Text2 is created by
6. Add the following code to the GotFocus event for Text2:
Set ControlWithFocus = Text2
7. Add a Command Button control to Form1. Command1 is created by
default. Set its Caption property to "Help".
8. Add the following code to the Click event for Command1:
Dim RVal As Integer
RVal = WinHelp(Form1.hWnd, "c:\vb\vb.hlp", HELP_CONTENTS, 0)
Run the program. There are two Text Box controls and one Command
Button control shown on the form. Notice that Text1 currently has the
focus. Click the Command Button to display the Contents window in
Help. Exit Help. The Text1 control should still have the focus. Move
the focus to the second Text Box control, Text2. Click the Help
command button a second time and exit Help. The second Text Box
control should have the focus. The Command Button control never
retains the focus.