Richer RichTextBox (Part 2) - The Code Projec...

 
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Richer RichTextBox (Part 2)
ByNikola Stepan.
An article on extending the RichTextBox class in C#.
C#
Windows, .NET (.NET 1.1)
Win32, VS (VS.NET2003)
Dev
Posted: 9 Nov 2005
Updated: 13 Jan 2006
Views: 19,547
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Introduction
In thefirst part, we extended the RichTextBox class with methods that change the FontStyle of a selection without losing the styles that are currently present. Unfortunately, there are a few more features missing from the RichTextBox control that could potentially be useful in word-processor-like applications. These kinds of applications commonly use a status bar to display information about the current cursor position. In this part, we will enrich the RichTextBox control with functionality that can be used for that purpose.
Usage
When nothing is selected, we want to display line number, column number and cursor position. When some portion of text is selected, the status bar should display the start, end and length of the selection. Also, from the client perspective, those features should be self-documentary and easy to use.
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this.rtb.CursorPositionChanged += new System.EventHandler(this.rtb_CursorPositionChanged); this.rtb.SelectionChanged += new System.EventHandler(this.rtb_SelectionChanged); . . . private void rtb_CursorPositionChanged(object sender, System.EventArgs e) { int line = rtb.CurrentLine; int col = rtb.CurrentColumn; int pos = rtb.CurrentPosition; statusBar.Text = "Line " + line + ", Col " + col + ", Position " + pos; } private void rtb_SelectionChanged(object sender, System.EventArgs e) { int start = rtb.SelectionStart; int end = rtb.SelectionEnd; int length = rtb.SelectionLength; statusBar.Text = "Start " + start + ", End " + end + ", Length " + length; }
To achieve such behavior, we need to extend the RichTextBox class in the following manner:
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using System; using System.Drawing; using System.Windows.Forms; namespace Nik.UserControls { public class RicherTextBox2 : System.Windows.Forms.RichTextBox { public event EventHandler CursorPositionChanged; protected virtual void OnCursorPositionChanged( EventArgs e ) { if ( CursorPositionChanged != null ) CursorPositionChanged( this, e ); } protected override void OnSelectionChanged( EventArgs e ) { if ( SelectionLength == 0 ) OnCursorPositionChanged( e ); else base.OnSelectionChanged( e ); } public int CurrentColumn { get { return CursorPosition.Column( this, SelectionStart ); } } public int CurrentLine { get { return CursorPosition.Line( this, SelectionStart ); } } public int CurrentPosition { get { return this.SelectionStart; } } public int SelectionEnd { get { return SelectionStart + SelectionLength; } } } internal class CursorPosition { [System.Runtime.InteropServices.DllImport("user32")] public static extern int GetCaretPos(ref Point lpPoint); private static int GetCorrection(RichTextBox e, int index) { Point pt1 = Point.Empty; GetCaretPos(ref pt1); Point pt2 = e.GetPositionFromCharIndex(index); if ( pt1 != pt2 ) return 1; else return 0; } public static int Line( RichTextBox e, int index ) { int correction = GetCorrection( e, index ); return e.GetLineFromCharIndex( index ) - correction + 1; } public static int Column( RichTextBox e, int index1 ) { int correction = GetCorrection( e, index1 ); Point p = e.GetPositionFromCharIndex( index1 - correction ); if ( p.X == 1 ) return 1; p.X = 0; int index2 = e.GetCharIndexFromPosition( p ); int col = index1 - index2 + 1; return col; } } } Resources
Inheriting from a Windows Forms Control with Visual C#.CalcSharp support site.
Nikola Stepan
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Subject  Author  Date

 Finding Text Position  mark_e_mark  10:49 30 Mar ‘06
  Hi Nikola,
Great Article!
I was wondering if you have know of a way that I can extract the text from a RTB and find the position each char is in the display?
I know its a wierd thing to do but I really need to do it...
Regards
Mark
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 Problem with column position  gijsvennix  7:29 2 Jan ‘06
  There seems to be a bug in the columnposition in the statusbar. It happens under the following conditions:
Turn off wordwrap on the rtb, type a line longer then the width so a horizontal scrollbar appears, scroll to the right. Now position the cursor somewhere on the line to see that the columnposition displayed is counted from the beginning of the visible part of the sentence. Not from the actual beginning of the sentence.
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 Re: Problem with column position  Nikola Stepan  9:46 13 Jan ‘06
  gijsvennix wrote:
There seems to be a bug in the columnposition in the statusbar. It happens under the following conditions:
Turn off wordwrap on the rtb, type a line longer then the width so a horizontal scrollbar appears, scroll to the right. Now position the cursor somewhere on the line to see that the columnposition displayed is counted from the beginning of the visible part of the sentence. Not from the actual beginning of the sentence.
I updated article and source code which should now work with both wordwrap on/off.
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 Re: Problem with column position  Ribeaucoup Thomas  4:05 14 Dec ‘06
  Greetings,
Thanks for the example!
I missed the function ‘GetLineFromCharIndex‘ in MSDN and it was exactly what I was looking for !
But I don‘t understand why you use point coordinates instead of using characters number calculation...
Moreover I don‘t understand the utility of the strange ‘GetCorrection‘ !
What about this much simpler and faster solution :
public int CurrentColumn
{
get
{
return SelectionStart - GetFirstCharIndexOfCurrentLine() + 1 ;
}
}
public int CurrentLine
{
get
{
return GetLineFromCharIndex( SelectionStart ) + 1 ;
}
}
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Updated: 13 Jan 2006 Article content copyright Nikola Stepan, 2005
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