History Edit Control - CodeProject

Sample Image - history_edit.gif

CHistoryEdit is a CEdit derived control that lets you to display a scrolling text history, much like Dev Studio's "Output" window during a compilation. The image presents an example of the control (the "History" window) being used in a dialog box.

CHistoryEdit's AppendString() method appends a text string to the control and automatically scroll the most recent entry into view. Two other methods, AllowSelection() and IsSelectable() allow you to control whether the user may select text in the control.

Using CHistoryEdit in a dialog is quite simple:

Include CHistoryEdit.h in your dialog class' header file.
Add member variables of type CHistoryEdit for every edit control you want to subclass.
Subclass the edit controls in your dialog's OnInitDialog() method.
```
m_HistoryEdit.SubclassDlgItem (EDIT_HISTORY, this);
```

Append text to the control by using AppendString().

m_HistoryEdit.AppendString ("Compiling D:\\XDA\\Test\\Mechanic.kb...");

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Ravi Bhavnani

Canada

Member

Ravi Bhavnani is an ardent fan of Microsoft technologies who loves building Windows apps, especially PIMs, system utilities, and things that go bump on the Internet. During his career, Ravi has developed expert systems, desktop imaging apps, marketing automation software, EDA tools, a platform to help people find, analyze and understand information, trading software for institutional investors and advanced data visualization solutions. He currently works for a company that provides enterprise workforce management solutions to large clients.

His interests include the .NET framework, reasoning systems, financial analysis and algorithmic trading, NLP, CHI and UI design. Ravi holds a BS in Physics and Math and an MS in Computer Science and was a Microsoft MVP (C++ and C# in 2006 and 2007). He is also the co-inventor of 2 patents on software security and generating data visualization dashboards. His claim to fame is that he crafted CodeProject's "joke" forum post icon.

Ravi's biggest fear is that one day he might actually get a life, although the chances of that happening seem extremely remote.

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Limited buffer [modified]

Pandele Florin

23:47 24 Aug '06

I think it is a good idea to limit the amount of text that this edit control diplays.This should be placed in CHistoryEdit::AppendString to do that:



 str += "\r\n";

 

    SetRedraw(FALSE);

 

    int start, end;

    GetSel(start, end);	

    DWORD len = GetWindowTextLength();

   

	if (len>MAXCHARS) 

	{

	int toline= LineFromChar(len-MAXCHARS);

	if (LineIndex(toline) != -1)

		{		   

		   SetSel(0, LineIndex(toline)+LineLength(toline));

		   ReplaceSel("");

		}

	}

		

	SetSel(len, len, TRUE);

    ReplaceSel(str);

    SetSel(start, end, TRUE);

    SetRedraw(TRUE);

 



    DWORD newLen = GetWindowTextLength();

    SetSel(newLen, newLen, FALSE);

You should as well define MAXCHARS to the desired maximum number of chars to allow.It should be under 64k(Ansi)32k(Unicode).
I got inspired by Kupriyanov Anatolij's message.

Re: Limited buffer

Ravi Bhavnani

2:12 25 Aug '06

Good point! I'll update the article soon. Thanks, /ravi My new year's resolution: 2048 x 1536 Home \| Music \| Articles \| Freeware \| Trips ravib(at)ravib(dot)com
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Re: Limited buffer

Widdis

9:54 17 Jan '07

First of all, Thank you for this control. This is exactly what I needed for my app.

You may also want to be able to limit the number of lines that you can have in the edit box. This can be easily done:

- add member m_maxLines
- add accessor / mutator and a default value
- add the following code to AppendString:

SetRedraw(FALSE);

....

SetWindowText(strBuffer);

//New code to limit number of lines

if (GetLineCount() > m_maxLines)
{
int nDel = 0;
for (int i = 0; i < GetLineCount() - m_maxLines; i++)
{
nDel += strBuffer.Find("\n", nDel) + 1;
}

SetSel(0, nDel, TRUE);
ReplaceSel("");
}

SetRedraw(TRUE);

//End new code

LineScroll( GetLineCount(), 0);

....

SubClass

xavigonzalvo

23:05 4 Nov '04

Why do you have to subclass the control?
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A good one routine

Kupriyanov Anatolij

21:08 23 Aug '04

I introduce good routine for appending string to control.

void CEditHistoryView::AppendLine(CString text)
{
     text += "\r\n";

     SetRedraw(FALSE);

     int start, end;
     GetSel(start, end);
     DWORD len = GetWindowTextLength();
     SetSel(len, len, TRUE);
     ReplaceSel(text);
     SetSel(start, end, TRUE);

     SetRedraw(TRUE);

     if(start == end && len == start)
     {// If cursor was at end of box, then scroll to the end
          DWORD newLen = GetWindowTextLength();
          SetSel(newLen, newLen, FALSE);
     }
}

WBR, kan

flickering problem

Anonymous

0:06 23 Apr '02

The problem with your solution is flickering. How do you avoid it ?
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mod for variable args

Glenn

9:40 10 Aug '01

Here's a slight modification to allow variable args like printf. I also changed the CString arg to a LPCSTR because it avoids unnecessary construction of a CString. Current calls to the AppendString method don't change.

----------
// HistoryEdit.h

// ...
#ifndef _HistoryEdit_h_
#define _HistoryEdit_h_

#include
// ...

// Operations
public:
void AppendString (LPCSTR str, ...);

// ...

----------
// HistoryEdit.cpp

// ...

void CHistoryEdit::AppendString
(LPCSTR str, ... )
{
CString strBuffer; // current contents of edit control

va_list marker;
va_start( marker, str );

TCHAR szBuf[ 4096 ];
_vsnprintf( szBuf, sizeof szBuf, str, marker );
va_end( marker );
CString strNew( szBuf );
strNew.Replace( _T("\n"), _T("\r\n") );

// Append string
GetWindowText (strBuffer);

if ( !strBuffer.IsEmpty() && strBuffer.Right(1).Compare( _T("\n") ) )
strBuffer += "\r\n";

strBuffer += strNew;
SetWindowText (strBuffer);

// Scroll the edit control
LineScroll (GetLineCount(), 0);
}

// ...

Glenn

Q:further mimicking devstudio's outputwindow

Paul Kuijten

14:44 11 Mar '00

I'm trying to expand this thingie to only scroll if the caret is on the last line of the editcontrol. Now that's not hard, but the hard part is the repositioning of the caret/selection after the adding of text, Any Ideas?

so far I've come up with this (which works partially):

void CLogDlg::DisplayLogMessage(CString string)
{

//determine if selection on last row
BOOL bscroll = FALSE;
if (m_ctrlLogEdit.LineFromChar /
(m_ctrlLogEdit.LineIndex()) /
== m_ctrlLogEdit.GetLineCount() - 1)
{
bscroll = TRUE;
}

//add carriage return linefeed
string += "\r\n";

//Get your original selection
if (!bscroll)
{
int start;
int end;
m_ctrlLogEdit.GetSel(start, end);
}

int len = m_ctrlLogEdit.GetWindowTextLength();

//append string
m_ctrlLogEdit.SetSel(len, len);
m_ctrlLogEdit.ReplaceSel(string);

//reset to your original selection or scroll
if (!bscroll)
m_ctrlLogEdit.SetSel(start, end);
else
{
m_ctrlLogEdit.LineScroll /
(m_ctrlLogEdit.GetLineCount(), 0);
len = m_ctrlLogEdit.GetWindowTextLength();
//be on last line next time
m_ctrlLogEdit.SetSel(len, len);
}