Microsoft KB Archive/198649

= ACC2000: How to Limit Number of Characters to Size of Text Box =

Article ID: 198649

Article Last Modified on 6/23/2005

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APPLIES TO


 * Microsoft Access 2000 Standard Edition

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This article was previously published under Q198649



Advanced: Requires expert coding, interoperability, and multiuser skills.

For a Microsoft Access 2002 version of this article, see 324584.

For a Microsoft Access 97 version of this article, see 152475.



SUMMARY
This article shows you how to limit the amount of text a user can type into a text box so that the width of the text does not exceed the width of the text box.

NOTE: This article explains a technique demonstrated in the sample file, FrmSmp00.mdb. For information about how to obtain this sample file, please see the following article in the Microsoft Knowledge Base:

233324 Microsoft Access 2000 Sample Forms Database Available in Download Center

Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements.



MORE INFORMATION
What follows is a Visual Basic for Applications procedure, LimitTextToControlWidth, that you can call from the KeyPress event of a text box to limit the amount of text a user can enter.

This procedure is ideal for developers who want to use a non- proportionally spaced font to print text into a fixed location on a pre- printed form. The LimitTextToControlWidth procedure ensures that a user will not be able to type more text than can fit in the defined area on the form.

A number of factors affect the width of text. The larger the font size, the fewer the characters that you can type. The font that you select also affects the width of characters in the text. Characters in a non-proportionally spaced font, such as Arial or Times New Roman, have different widths. The letter "i" is narrower in width than the letter "X." In addition, the letter "i" in one font may have a different width in another font. For example, the "i" in Arial font is much narrower than the "i" in Courier New font.

The following steps provide both 16-bit and 32-bit versions of the procedure, followed by an example of how to apply the procedure to controls on a form.

NOTE: The following code uses the GetTextExtentPoint Windows application programming interface (API) function. You can call this API function only from the control that has focus on an Access form.

  Create a new module and type the following in the Declarations section: Option Explicit

Const LOGPIXELSX = 88 Const LOGPIXELSY = 90 Const TWIPSPERINCH = 1440

Type Size cx As Long cy As Long End Type

Declare Function GetDC Lib "user32" (ByVal hWnd As Long) As Long Declare Function GetDeviceCaps Lib "gdi32" (ByVal hDC As Long, _  ByVal nIndex As Long) As Long Declare Function GetFocus Lib "user32" As Long Declare Function GetTextExtentPoint Lib "gdi32" Alias _ "GetTextExtentPointA" (ByVal hDC As Long, ByVal lpsz As String, _  ByVal cbString As Long, lpSIZE As Size) As Long Declare Function ReleaseDC Lib "user32" (ByVal hWnd As Long, _  ByVal hDC As Long) As Long

  Type the following procedures: Sub ConvertPixelsToTwips(X As Long, Y As Long) Dim hDC As Long, hWnd As Long, RetVal As Long Dim XPIXELSPERINCH As Long, YPIXELSPERINCH As Long

 Retrieve the current number of pixels per inch, which is   resolution-dependent. hDC = GetDC(0) XPIXELSPERINCH = GetDeviceCaps(hDC, LOGPIXELSX) YPIXELSPERINCH = GetDeviceCaps(hDC, LOGPIXELSY) RetVal = ReleaseDC(0, hDC)

'' Compute and return the measurements in twips. X = (X / XPIXELSPERINCH) * TWIPSPERINCH Y = (Y / YPIXELSPERINCH) * TWIPSPERINCH End Sub

Sub LimitTextToControlWidth(KeyAscii As Integer) Dim AC As Control Dim Txt As String Dim TxtWidth As Long, SpaceWidth As Long Dim hWnd As Long, hDC As Long Dim lpSIZE As Size Dim RetVal As Long

'' Exit if a non-printable character is typed. If KeyAscii < 32 Then Exit Sub

'' Record active control. Set AC = Screen.ActiveControl

'' Get the control text. Txt = AC.Text & ""

'' Append typed character into the text. If KeyAscii > 32 Then Txt = Left(Txt, AC.SelStart) Txt = Txt & Chr$(KeyAscii) Txt = Txt & Mid(Txt, AC.SelStart + 1 + AC.SelLength) End If

hWnd = GetFocus hDC = GetDC(hWnd)

'' Compute the width of the text. RetVal = GetTextExtentPoint(hDC, Txt, Len(Txt), lpSIZE) ConvertPixelsToTwips lpSIZE.cx, lpSIZE.cy  TxtWidth = lpSIZE.cx

'' Compute width of a space. RetVal = GetTextExtentPoint(hDC, " ", 1, lpSIZE) ConvertPixelsToTwips lpSIZE.cx, lpSIZE.cy  SpaceWidth = lpSIZE.cx

'' Are there trailing spaces to contend with? If AC.SelStart + 1 > Len(Txt) Then '' Add number of spaces * SpaceWidth to width of string. TxtWidth = TxtWidth + ((AC.SelStart + 1 - Len(Txt)) * _         SpaceWidth) End If

If TxtWidth + (SpaceWidth / 2) > AC.Width Then Beep KeyAscii = 0 End If

End Sub



How to use the LimitTextToControlWidth Procedure
  Create a new, blank form not based on any table or query, with the following properties:   Form: Test1 -  Caption: TestForm

Text box ---  Name: One Left: 1"  Top: .5" Width: 1"  Height: 0.1667" FontName: Arial FontSize: 12

Text box ---  Name: Two Left: 1"  Top: 1" Width: 1"  Height: 0.1667" FontName: Arial FontSize: 8

Text box ---  Name: Three Left: 1"  Top: 1.5" Width: 1"  Height: 0.3743" FontName: Arial FontSize: 24   Call the LimitTextToControlWidth procedure from the KeyPress event of each text box above, for example: Sub One_KeyPress(KeyAscii As Integer) LimitTextToControlWidth KeyAscii End Sub   View the form and try typing the following text in each text box:

This is a test of the emergency broadcast system

Note that the result appears as follows: <pre class="fixed_text">  Text box     Text allowed to type -  One          This is a test Two         This is a test of the Three       This is                    </li></ol>

Keywords: kbhowto kbusage KB198649

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