ID: Q152475
The information in this article applies to:
Advanced: Requires expert coding, interoperability, and multiuser skills.
This article shows you how to limit the amount of text typed into a text box so that the width of the text does not exceed the width of the text box.
This article assumes that you are familiar with Visual Basic for Applications and with creating Microsoft Access applications using the programming tools provided with Microsoft Access. For more information about Visual Basic for Applications, please refer to your version of the "Building Applications with Microsoft Access" manual.
NOTE: Visual Basic for Applications is called Access Basic in Microsoft Access version 2.0. For more information about Access Basic, please refer to the "Building Applications" manual.
NOTE: This article explains a technique demonstrated in the sample files, FrmSampl.exe (for Microsoft Access for Windows 95 version 7.0) and FrmSmp97.exe (for Microsoft Access 97). For information about how to obtain these sample files, please see the following articles in the Microsoft Knowledge Base:
ARTICLE-ID: Q150895
TITLE : ACC95: Microsoft Access Sample Forms Available on MSL
ARTICLE-ID: Q175066
TITLE : ACC97: Microsoft Access 97 Sample Forms Available on MSL
The following information includes a Visual Basic for Applications procedure, LimitTextToControlWidth, that can be called from the KeyPress event of a text box to limit the amount of text entered so that the sum of the width of all characters in the text does not exceed the width of the text box.
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.
There are a number of factors that affect the width of text. The larger the font size, the fewer the characters that you will be able to type. The selection of font 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, for the same font size, the letter "i" in one font may have a different width in another font. 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. This API function can only be called from the control that has focus on a Microsoft Access form.
1. 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
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
NOTE: In the following sample code, an underscore (_) at the end of a line is used as a line-continuation character. Remove the underscore from the end of the line when re-creating this code in Access Basic,
1. 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 Integer
cy As Integer
End Type
Declare Function GetDC Lib "User" (ByVal hWnd As Integer) As Integer
Declare Function GetDeviceCaps Lib "GDI" (ByVal hDC As Integer, _
ByVal nIndex As Integer) As Integer
Declare Function GetTextExtentPoint Lib "GDI" (ByVal hDC As _
Integer, ByVal lpszString As String, ByVal cbString As _
Integer, lpSIZE As SIZE) As Integer
Declare Function GetFocus Lib "User" () As Integer
Declare Function ReleaseDC Lib "User" (ByVal hWnd As Integer, _
ByVal hDC As Integer) As Integer
Sub LimitTextToControlWidth (KeyAscii)
Dim AC As Control
Dim Txt As String
Dim TxtWidth As Integer, SpaceWidth As Integer
Dim hWnd As Integer, hDC As Integer
Dim lpSIZE As SIZE
Dim RetVal As Integer
'' 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
Sub ConvertPixelsToTwips (X As Integer, Y As Integer)
Dim hDC As Integer, hWnd As Integer, RetVal As Integer
Dim XPIXELSPERINCH As Integer, YPIXELSPERINCH As Integer
'' 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
1. Create a new, blank form not based on any table or query.
2. Place 3 text boxes on the form with the following properties:
Name: One
Left: 1"
Top: .5"
Width: 1"
Height: 0.1667"
FontName: Arial
FontSize: 12
Name: Two
Left: 1"
Top: 1"
Width: 1"
Height: 0.1667"
FontName: Arial
FontSize: 8
Name: Three
Left: 1"
Top: 1.5"
Width: 1"
Height: 0.3743"
FontName: Arial
FontSize: 24
each text box above, for example:
Sub One_KeyPress(KeyAscii As Integer)
LimitTextToControlWidth KeyAscii
End Sub
This is a test of the emergency broadcast system
Note that the result appears as follows:
Text box Text allowed to type
---------------------------------
One This is a test
Two This is a test of the
Three This is
Keywords : kbusage FmsHowto
Version : 2.0 7.0 97
Platform : WINDOWS
Hardware : x86
Issue type : kbhowtoLast Reviewed: November 21, 1998