Past Tips of the Week

You can't increment a vertical scroll bar's value -- a fact that can become annoying. For example, start a new project and place a text box and a vertical scroll bar on the form. Place the vertical scroll bar to the right of the text box and assign their Height and Top properties the same values. Assign the vertical scroll bar a Min property value of 1 and a Max value of 10. Place the following code in the vertical scroll bar's Change event:

Text1.Text = VScroll1.Value

Now press [F5] to run the project. Notice that if you click on the bottom arrow of the vertical scroll bar, the value increases; if you click on the top arrow, the value decreases. From my perspective, it should be the other way around.

To correct this, change the values of the Max and Min properties to negative values. For example, end the program and return to the design environment. Change the vertical scroll bar's Max value to -1 and its Min value to -10. In its Change event, replace the line you entered earlier with the following:

Text1.Text = Abs(Vscroll1.Value)

Now press [F5] to run the project. When you click on the top arrow of the vertical scroll bar, the value now increases. Adjust the Height properties of the text box and the scroll bar so you can't see the position indicator, and your number box is ready to go.

It's very simple to determine the extent of a string in VB. You can do so with WinAPI functions, but there's an easier way: Use the AutoSize property of a Label component. First, insert a label on a form (labMeasure) and set its AutoSize property to True and Visible property to False. Then write this simple routine:

Private Function TextExtent(txt as String) as Integer
   labMeasure.Caption = txt
   TextExtent = labMeasure.Width
End Function When you want to find out the extent of some text, simply call this function with the string as a parameter.

In my case it turned out that the measure was too short. I just added some blanks to the string. For example:

You can use just a few lines of code to import Registry settings. If you have an application called myapp.exe and a Registry file called myapp.reg, the following code will put those settings into the Registry without bothering the user.

Both Access and VB let you hard code the file numbers when using the File Open statement. For example:

     Open "myfile.txt" for Append as #1
     Print #1,"a line of text"
     Close #1

The problem with this method of coding is that you never know which file numbers may be in use somewhere else in your program. If you attempt to use a file number already occupied, you'll get a file error. To prevent this problem, you should always use the FreeFile function. This function will return the next available file number for your use. For example:

     IntFile=FreeFile()
     Open "myfile.txt" for Append as #intFile
     Print #intFile,"a line of text"
     Close #intFile

Here's a great way to stop the user from running your application in the wrong screen resolution. First, create a function called CheckRez:

Public Function CheckRez(pixelWidth As Long, pixelHeight As Long) As Boolean
    '
    Dim lngTwipsX As Long
    Dim lngTwipsY As Long
    '
    ' convert pixels to twips
    lngTwipsX = pixelWidth * 15
    lngTwipsY = pixelHeight * 15
    '
    ' check against current settings
    If lngTwipsX <> Screen.Width Then
        CheckRez = False
    Else
        If lngTwipsY <> Screen.Height Then
            CheckRez = False
        Else
            CheckRez = True
        End If
    End If
    '
End Function

Next, run the following code at the start of the program:

    If CheckRez(640, 480) = False Then
        MsgBox "Incorrect screen size!"
    Else
        MsgBox "Screen Resolution Matches!"
    End If

When working with data entry controls, the current value in the control often needs to be selected when the control received focus. This allows the user to immediately begin typing over any previous value. Here's a quick subroutine to do just that:

Public Sub FocusMe(ctlName As Control)
    '
    With ctlName
        .SelStart = 0
        .SelLength = Len(ctlName)
    End With
    '
End Sub

Now add a call to this subroutine in the GotFocus event of the input controls:

Private Sub txtFocusMe_GotFocus()
    Call FocusMe(txtFocusMe)
End Sub

To add fully functional drag and drop to your forms, all you need to do is set the OLEDragMode property and OLEDropMode property of the input controls to "Automatic." This works across forms and even across applications on the same workstation. To test this, add two text boxes to a form. Use the Property Window to set the OLEDragMode and OLEDropMode properties to "Automatic." Now run the app and enter text in one text box and drag and drop it into the other text box.

Hint: Some controls only support OLEDrag. A few others do not support OLEDrag or OLEDrop. To determine what a control supports, check for the OLEDragMode and OLEDropMode properties. If their missing the control does not support OLEDrag and/or OLEDrop.

You can use the ParamArray keyword in the declaration line of a method to create a subroutine or function that accepts an arbitrary number of parameters at runtime. For example, you can create a method that will fill a list box with some number of items even if you do not know the number of items you will be sent. Add the method below to a form:

Public Sub FillList(ListControl As ListBox, ParamArray Items())
    '
    Dim i As Variant
    '
    With ListControl
        .Clear
        For Each i In Items
            .AddItem i
        Next
    End With
    '
End Sub

Note that the ParamArray keyword comes BEFORE the parameter in the declaration line. Now add a list box to your form and a command button. Add the code below in the "Click" event of the command button.

Private Sub Command1_Click()
    '
    FillList List1, "TiffanyT", "MikeS", "RochesterNY"
    '
End Sub

If you're using an ODBC connection to your database, you can ease the process of installing the application on workstations by using the FileDSN (data source name) instead of the more-common UserDSN. You define your ODBC connection as you normally would with UserDSNs. However, the resulting definition is not stored in the workstation registry. Instead it gets stored in a text file with the name of the DSN followed by ".dsn" (i.e. "MyFileDSN.dsn"). The default folder for all FileDSNs is "c:\program files\common files\Odbc\data sources". Now, when you want to install the VB application that uses the FileDSN, all you need to do is add the FileDSN to the Install package and run the install as usual. No more setting up DSNs manually!

NOTE: FileDSNs are available with ODBC 3.0 and higher.

You can create your own VB Templates quickly and easily. If you find that you are adding the same routines to your forms, classes, BAS modules, etc. you can build generic versions and place them in the Templates folder tree of VB5. By placing the coding module (frm, bas.cls, etc.) in the proper subfolder of the Templates folder, you'll see the new item appear whenever you select the Add... dialog box. You can add as many controls, library references, and lines of code as you wish to the templates.

CAUTION: If you uninstall VB5, you may loose your Templates folder and all its contents. Be sure to keep a secured copy of all your template files in a safe location.

Ever wonder how the SETUP.EXE screen gets its cool shaded background coloring? This color shading is called dithering, and you can easily incorporate it into your forms. Add the following routine to a form:

   Sub Dither(vForm As Form)
   Dim intLoop As Integer
      vForm.DrawStyle = vbInsideSolid
      vForm.DrawMode = vbCopyPen
      vForm.ScaleMode = vbPixels
      vForm.DrawWidth = 2
      vForm.ScaleHeight = 256
      For intLoop = 0 To 255
         vForm.Line (0, intLoop)-(Screen.Width, intLoop - 1), RGB(0, 0, 255 -intLoop), B
      Next intLoop
   End Sub

Now, add to the Form_Activate event the line

   Dither ME

This version creates a fading blue background by adjusting the blue value in the RGB function. (RGB stands for Red-Green-Blue.) You can create a fading red background by changing the RGB call to

   RGB(255 - intLoop, 0, 0).

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