Microsoft KB Archive/141073

= Using Windows API Functions to Better Manipulate Text Boxes =

Article ID: 141073

Article Last Modified on 1/8/2003

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APPLIES TO


 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 16-bit Enterprise Edition

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This article was previously published under Q141073



SUMMARY
By calling Windows API functions from Microsoft Visual Basic for Windows, you can retrieve text box (or edit control) information that you cannot obtain using only Visual Basic for Windows's built-in features.

NOTE: In Visual Basic versions 2.0, 3.0, and 4.0 for Windows, you can use the new HWND property of a text box instead of calling the GetFocus function.

This article supplies a sample program that performs the following useful features (making use of the Windows message constants shown in parentheses, obtained by calling Windows API routines):


 * Copies a specific line of text from the text box (EM_GETLINE).
 * Retrieves the number of lines within the text box (EM_GETLINECOUNT).
 * Positions the cursor at a specific character location (EM_GETSEL) in the text box.
 * Retrieves the line number of a specific character location in the text box (EM_LINEFROMCHAR).
 * Retrieves the amount of lines before a specified character position in the text box (EM_LINEINDEX).
 * Retrieves the amount of characters in a specified line in the text box (EM_LINELENGTH).
 * Replaces specified text with another text string (EM_REPLACESEL).

For additional information, please see the following article in the Microsoft Knowledge Base:

72677 : How to Limit User Input in VB Combo Box with SendMessage API



MORE INFORMATION
NOTE: As of 3/25/92, the code below corrects the VBknowlg.hlp file shipped with the Microsoft Professional Toolkit for Visual Basic version 1.0 for Windows.

NOTE: Using the SelStart, SelLength, and SelText properties may be easier than using EM_GETSEL and EM_REPLACESEL below.

The Windows API file User.exe defines the SendMessage function that returns or performs a specific event on your edit control. To create an example that displays specific information about your edit control, do the following:

  Create a form (Form1), and add the following controls and properties:   Control    Control Name    Height   Left    Top     Width

Label     aGetLine                 360     120 Label     aGetLineCount            360     480 Label     aGetSel                  360     840 Label     aLineFromChar            360     1200 Label     aLineIndex               360     1560 Label     aLineLength              360     1920 Label     aReplaceSel              360     2280 Command   Command1        375      360     2640    1815 Text      Text1           1815     2640    480     3495 Text      Text2           375      2520    2640    3615

 Set each label's AutoSize property to True. Set the Text1.MultiLine property to True. Change the Command1.Caption to "Insert this text --->".  Add the following code to the global Declarations section of Form1: Private Declare Function GetFocus% Lib "user" ' Enter the following Declare as one, single line:

Private Declare Function SendMessage& Lib "user"(ByVal hWnd%, ByVal        wMsg%, ByVal wParam%, ByVal lParam As Any)

' lParam is actually a double word, or long, but declaring ' lParam "As Any" allows flexibility for certain cases of     ' using SendMessage.

  After adding the code listed below to your form, run the program. Whenever a key is released, the labels are updated with the new information about your text box: Private Sub Form_Load Show X% = fReplaceSel("")  '* Used to display the correct text. End Sub

Private Sub Text1_KeyUp (KeyCode As Integer, Shift As Integer) '* Update the text control information whenever the key '* is pressed and released. CharPos& = fGetSel LineNumber& = fLineFromChar(CharPos&) X% = fGetLine(LineNumber&) X% = fGetLineCount X% = fLineIndex(LineNumber&) X% = fLineLength(CharPos&) End Sub

Private Sub Command1_Click '* This routine will insert a line of text at the current location '* of the caret.

D$ = Text2.text CharPos& = fGetSel X% = fReplaceSel(D$) X% = fSetSel(CharPos&)

'* Text has been inserted at the caret location. No update the '* text controls information. Call Text1_KeyUp(0, 0) Text1.SetFocus End Sub

Private Function fGetLineCount& '* This function return the number of lines in the edit control. Const EM_GETLINECOUNT = &H400 + 10

Text1.SetFocus ' In versions 2.0 3.00, you need to use a long integer to avoid ' a bad DLL calling convention error message. As an alternative, ' you can use the new HWND property instead of GetFocus: Pos& = SendMessage(GetFocus, EM_GETLINECOUNT, 0&, 0&) ' Use the following Pos& if you have Visual Basic version 1.0: ' Pos& = SendMessage(GetFocus, EM_GETLINECOUNT, 0%, 0%) aGetLineCount.Caption = "GetLineCount = " + Str$(Pos&) fGetLineCount = Pos& End Function

Private Function fGetLine (LineNumber As Long) '* This function copies a line of text specified by LineNumber '* from the edit control. The first line starts at zero.

Const MAX_CHAR_PER_LINE = 80 Const EM_GETLINE = &H400 + 20

byteLo% = MAX_CHAR_PER_LINE And (255) '[changed 3/25/92] byteHi% = Int(MAX_CHAR_PER_LINE / 256) '[changed 3/25/92, 2 lines:] Buffer$ = chr$(byteLo%) + chr$(byteHi%) + Space$(MAX_CHAR_PER_LINE-2)

Text1.SetFocus Pos& = SendMessage(GetFocus, EM_GETLINE, CINT(LineNumber), Buffer$) aGetLine.Caption = "GetLine = " + Buffer$ fGetLine = Pos&

End Function

Private Function fGetSel& '* This function returns the starting/ending position of the '* current selected text. This is the current location of the '* cursor if start is equal to ending. '* LOWORD-start position of selected text. '* HIWORD-first no selected text.

Const EM_GETSEL = &H400 + 0

Text1.SetFocus location& = SendMessage(GetFocus, EM_GETSEL, 0, 0&) ending% = location& \ &H10000 starting% = location& And &H7FFF aGetSel.Caption = "Caret Location = " + Str$(starting%) fGetSel = location& mod 65536 End Function

Private Function fLineFromChar& (CharPos&) '* This function will return the line number of the line that '* contains the character whose location(index) specified in the '* third argument of SendMessage. If the third argument is -1, '* then the number of the line that contains the first character '* of the selected text is returned. If start = end from GetSel, '* then the current caret location is used. Line numbers start '* at zero.

Const EM_LINEFROMCHAR = &H400 + 25

Text1.SetFocus Pos& = SendMessage(GetFocus, EM_LINEFROMCHAR, CINT(CharPos&), 0&) aLineFromChar.Caption = "Current Line = " + Str$(Pos&) fLineFromChar = Pos& End Function

Private Function fLineIndex (LineNumber As Long) '* This function will return the number of bytes that '* precede the given line. The returned number reflects the CR/LF '* after each line. The third argument to SendMessage specifies '* the line number, where the first line number is zero. If the '* third argument to SendMessage is -1, then the current line '* number is used.

Const EM_LINEINDEX = &H400 + 11

Text1.SetFocus Pos& = SendMessage(GetFocus, EM_LINEINDEX, CINT(LineNumber), 0&) aLineIndex.Caption = "#Char's before line = " + Str$(Pos&) fLineIndex = Pos& End Function

Private Function fLineLength& (CharPos As Long) '* This function will return the length of a line in the edit '* control. CharPos specifies the index of the character that '* is part of the line that you would like to find the length. If        '* this argument is -1, the current selected character is used as         '* the index.

Const EM_LINELENGTH = &H400 + 17 Text1.SetFocus Pos& = SendMessage(GetFocus, EM_LINELENGTH, CINT(CharPos), 0&) aLineLength.Caption = "LineLength = " + Str$(Pos&) fLineLength = Pos& End Function

Private Function fSetSel& (Pos&) '* This function selects all characters in the current text that '* are within the starting and ending positions given by        '* Location. The low word is the starting position and the high '* word is the ending position. If you set start to end, this '* can be used to position the cursor within the edit control.

Const EM_SETSEL = &H400 + 1 location& = Pos& * 2 ^ 16 + Pos& Text1.SetFocus X% = SendMessage(GetFocus, EM_SETSEL, 0%, location&) fSetSel = Pos& End Function

Private Function fReplaceSel (Buffer$) '* This function will replace the current selected text with the '* new text specified in Buffer$. You must call SendMessage with '* the EM_GETSEL constant to select text.

Const EM_REPLACESEL = &H400 + 18 Text1.SetFocus Pos& = SendMessage(GetFocus, EM_REPLACESEL, 0%, Buffer$) aReplaceSel.Caption = "String inserted = " + Buffer$ fReplaceSel = Pos& End Function </li></ol>

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