VB3 Use Windows API Functions to Better Manipulate Text Boxes
ID: Q76518
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The information in this article applies to:
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Microsoft Visual Basic Professional Edition for Windows, versions 1.0, 2.0, 3.0
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' built-in features.
NOTE: In Visual Basic versions 2.0 and 3.0 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):
- Copy a specific line of text from the text box (EM_GETLINE).
- Retrieve the number of lines within the text box (EM_GETLINECOUNT).
- Position the cursor at a specific character location (EM_GETSEL) in the
text box.
- Retrieve the line number of a specific character location in the text
box (EM_LINEFROMCHAR).
- Retrieve the amount of lines before a specified character position in
the text box (EM_LINEINDEX).
- Retrieve the amount of characters in a specified line in the text box
(EM_LINELENGTH).
- Replace specified text with another text string (EM_REPLACESEL).
For a separate article that explains how to specify the amount of text
allowable within a text control, query on the following word in the
Microsoft Knowledge Base:
EM_LIMITTEXT
MORE INFORMATION
NOTE: As of 3/25/92, the code below corrects the VBKNOWLG.HLP
file Knowledge Base 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
will return or perform a specific event on your edit control. To
create an example that will display 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:
Declare Function GetFocus% Lib "user" ()
' Enter the following Declare as one, single line:
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 will be updated with the new
information about your text box.
Sub Form_Load ()
Show
X% = fReplaceSel("") '* Used to display the correct text.
End Sub
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
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$)
X% = fSetSel(CharPos&)
'* Text has been inserted at the caret location. No update the
'* text controls information.
Call Text1_KeyUp(0, 0)
Text1.SetFocus
End Sub
Function fGetLineCount& ()
'* This function will return the number of lines in the edit control.
Const EM_GETLINECOUNT = &H400 + 10
Text1.SetFocus
' In versions 2.00 and 3.00, you need to use a long integer to avoid
' a bad DLL calling convention error message. As an alternative,
' you can use the new HWND property instead of GetFocus():
Pos& = SendMessage(GetFocus(), EM_GETLINECOUNT, 0&, 0&)
' Use the following Pos& if you have Visual Basic version 1.0:
' Pos& = SendMessage(GetFocus(), EM_GETLINECOUNT, 0%, 0%)
aGetLineCount.Caption = "GetLineCount = " + Str$(Pos&)
fGetLineCount = Pos&
End Function
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, two 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
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$(starting%)
fGetSel = location& mod 65536
End Function
Function fLineFromChar& (CharPos&)
'* This function will return the line number of the line that
'* contains the character whose location(index) specified in the
'* third argument of SendMessage. If the third argument is -1,
'* then the number of the line that contains the first character
'* of the selected text is returned. If start = end from GetSel,
'* then the current caret location is used. Line numbers start
'* at zero.
Const EM_LINEFROMCHAR = &H400 + 25
Text1.SetFocus
Pos& = SendMessage(GetFocus(), EM_LINEFROMCHAR, CINT(CharPos&), 0&)
aLineFromChar.Caption = "Current Line = " + Str$(Pos&)
fLineFromChar = Pos&
End Function
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$(Pos&)
fLineIndex = Pos&
End Function
Function fLineLength& (CharPos As Long)
'* This function will return the length of a line in the edit
'* control. CharPos specifies the index of the character that
'* is part of the line that you would like to find the length. If
'* this argument is -1, the current selected character is used as
'* the index.
Const EM_LINELENGTH = &H400 + 17
Text1.SetFocus
Pos& = SendMessage(GetFocus(), EM_LINELENGTH, CINT(CharPos), 0&)
aLineLength.Caption = "LineLength = " + Str$(Pos&)
fLineLength = Pos&
End Function
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
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
REFERENCES
"Programming Windows: The Microsoft Guide to Writing Applications for
Windows 3," Charles Petzold, Microsoft Press, 1990
"Microsoft Windows Software Development Kit: Reference Volume 1,"
version 3.0
WINSDK.HLP file shipped with Microsoft Windows 3.0 Software Development Kit
Additional query words:
1.00 2.00 3.00 docerr
Keywords : kbcode
Version : 1.00 2.00 3.00
Platform : WINDOWS
Issue type :
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