Q186271: HOWTO: Manipulate Text Box Contents
Article: Q186271
Product(s): Microsoft Visual Basic for Windows
Version(s):
Operating System(s):
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
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SUMMARY
=======
This article illustrates how to manipulate the contents of a text box by using a
combination of text box properties and calling functions from the Windows API.
You can use the techniques in this article to extend the features of a text box.
The article also shows you how to create a sample project that demonstrates how
to manipulate the contents of a text box.
MORE INFORMATION
================
This article assumes you are familiar with using the functions in the Windows
API. The article will show you how to do the following:
- Determine the cursor position in a text box.
- Determine the line number of the line where your cursor is positioned in a
multi-line text box.
- Determine the length of a selected line.
- Show all the text of a selected line.
- Insert text at a cursor position.
The first task uses a text box property. The remaining tasks use the SendMessage
API function with the handle of the text box, a message, and the parameters
required for that message.
To determine the cursor position in a text box, use the SelStart property of the
text box. This property returns the position of the text relative to the first
character of the first line. If you select a block of text, you can determine
the cursor position by adding the SelLength property to the SelStart property.
The other three tasks require the SendMessage function with the Hwnd property of
the text box, the appropriate message, and the required message parameters. The
declaration of the SendMessage function is as follows:
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
ByVal lParam As String) As Long
The following messages are used:
- EM_LINEFROMCHAR (&HC9)-returns the line number of the line where the
cursor is positioned. Pass the cursor position with this message.
- EM_LINELENGTH (&HC1)-returns the length of the line where the cursor is
positioned. Pass the cursor position with this message.
- EM_LINEINDEX (&HBB)-returns the number of characters in all the lines
previous to the cursor position. Pass the results of the EM_LINEFROMCHAR
message. Each line includes a carriage return and a line feed character.
- EM_GETLINECOUNT (&HBA)-returns the total number of lines in a multi-line
text box.
- EM_GETLINE (&HC4)-returns the text of the line where the cursor is
positioned. Pass the results of the EM_LINEFROMCHAR message.
The next section shows how to create a sample project that demonstrates how to
manipulate text in a text box.
Steps to Create Sample Project
------------------------------
1. Start a new Standard EXE project in Visual Basic. Form1 is created by
default.
2. Add a CommandButton, two Label controls and two Text boxes to Form1 and set
the following properties to the appropriate controls:
Control Default Name Property Setting
---------------------------------------------------------------
Text Box Text1 MultiLine True
Label Label1 AutoSize True
3. Copy the following code to the Code window of the Form1 form:
Option Explicit
Private Declare Function SendMessage Lib "user32" _
Alias "SendMessageA" _
(ByVal hwnd As Long, _
ByVal wMsg As Long, _
ByVal wParam As Long, _
ByVal lParam As String) _
As Long
Private Const EM_GETLINE = &HC4
Private Const EM_GETLINECOUNT = &HBA
Private Const EM_LINEFROMCHAR = &HC9
Private Const EM_LINEINDEX = &HBB
Private Const EM_LINELENGTH = &HC1
Private Const EM_REPLACESEL = &HC2
Private Sub Form_Load()
With Command1
.Caption = "Insert This Text"
.Height = 375
.Left = 120
.Top = 3000
.Width = 1455
End With
With Form1
.Caption = "Enhanced Text Box Sample Project"
.Height = 4485
.Width = 6990
End With
With Label1
.Height = 195
.Left = 120
.Top = 240
.Width = 3015
.WordWrap = True
End With
With Label2
.Height = 255
.Left = 1800
.Top = 3360
.Width = 3135
End With
With Text1
.Height = 2655
.Left = 3360
.Top = 240
.Width = 3375
End With
With Text2
.Height = 285
.Left = 1680
.Top = 3000
.Width = 5055
End With
End Sub
Private Sub Command1_Click()
Call SendMessage(Text1.hwnd, EM_REPLACESEL, 0, Text2.Text)
Label2.Caption = "Copied text is " + Text2.Text
ShowInfo
End Sub
Private Sub Text1_KeyUp(KeyCode As Integer, Shift As Integer)
ShowInfo
End Sub
Private Sub Text1_MouseMove(Button As Integer, _
Shift As Integer, _
X As Single, _
Y As Single)
ShowInfo
End Sub
Private Function ShowInfo()
'********************************************************************
' Purpose: Runs all the functions to get the necessary information
' in order to create the information text string. The text
' string is then displayed in the label control.
'********************************************************************
Dim strInfo As String
Dim lCurPos As Long
Dim lCurLineNum As Long, lTotLines As Long, lLineLength
Dim lNumBChar As Long
Dim sCurLine As String * 25
'Determine Cursor Position
If Text1.SelLength = 0 Then
lCurPos = Text1.SelStart
Else
lCurPos = Text1.SelStart + Text1.SelLength
End If
'Determine Line Number
lCurLineNum = SendMessage(Text1.hwnd, EM_LINEFROMCHAR, lCurPos, 0)
'Determine the Line Length
lLineLength = SendMessage(Text1.hwnd, EM_LINELENGTH, lCurPos, 0)
'Determine the number of characters in lines before current
'cursor position. Note that the number of characters includes a
'carriage return and line feed characters at the end of each
'line.
lNumBChar = SendMessage(Text1.hwnd, EM_LINEINDEX, lCurLineNum, 0)
'Determine Total number of lines
lTotLines = SendMessage(Text1.hwnd, EM_GETLINECOUNT, 0, 0)
'Determine Current Line
sCurLine = Space(25)
Call SendMessage(Text1.hwnd, EM_GETLINE, lCurLineNum, sCurLine)
'Display the information
strInfo = "Current Line: " + sCurLine + vbLf + _
"Line Length: " + CStr(lLineLength) + _
" Characters" + vbLf + _
"Line Number: " + CStr(lCurLineNum + 1) + _
" of " + CStr(lTotLines) + " Total Lines" + vbLf + _
"Cursor Position: " + CStr(lCurPos) + vbLf + _
"Total Characters in Previous Lines: " + _
CStr(lNumBChar) + vbLf + _
"Selected Length: " + CStr(Text1.SelLength) + vbLf + _
"Selected Text: " + Text1.SelText
Label1.Caption = strInfo
End Function
4. On the Run menu, click Start or press the F5 key to start the program. Click
inside the Text1 text box to display the text box information in Label1. To
insert text into the Text1 text box, position the cursor in the Text1 text
box where you want the text to be inserted. Enter the insertion text in the
Text2 text box and click the CommandButton.
(c) Microsoft Corporation 1998, All Rights Reserved.
Contributions by Fred Nava, Microsoft Corporation
(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Arsenio
Locsin, Microsoft Corporation
Additional query words: kbDSupport kbDSD kbSDKWin32 kbAPI kbVBp500 kbVBp600 kbVBp
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Keywords : kbGrpDSVB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Issue type : kbhowto
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