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Posted 5 Apr 2000
Licenced CPOL

CEditLog - fast logging into an edit control with cout

, 1 Nov 2003
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Use an edit control for logging messages and redirect cout


I once wanted to use an edit control for fast, asynchronous text output. I need to log messages from a lot of threads, sometimes more than 1000 per second. And since I created already functions to dump my objects to std::cout I also wanted to use an edit control as std::ostream.


  • Asynchronous, very fast output to any edit control
  • User can scroll back, select and copy text and so on during output
  • Can be used with or without MFC (Sample is a MFC project)
  • Uses window-subclassing, so you can use it even with CEdit-derived controls
  • Save to be used by multiple threads
  • Special basic_streambuf class to create or redirect a std::ostream (such as std::cout) to an edit control

Using CEditLog

Just create an Instance of CEditLog and attach an edit control to it using the SetEditControl() function. Then you can add text to the end of the edit control using one of the AddText() members:

class CEditLog : protected CSubclassWnd
    typedef CSubclassWnd root_type;

    // Constructs the CEditLog. You can pass the edit controls handle

    // here or set it later using the SetEditCtrl() function.

    // To increase performance CEditLog repaints the edit-control

    // only if the caret resides in the last line. Otherwise the

    // control will be refreshed only every nMaxRefreshDelay msec.

    CEditLog( HWND hEdit = NULL, UINT nMaxRefreshDelay = 500 );
    // Adds some text to the end of the edit control. Works asynchronously

    // (using PostMessage()) and is save to be called by multiple threads.

    // If you pass true for bLFtoCRLF every LF (ASCII 10) (as it is used in

    // most cases for end-of-line) will be converted to a CR/LF (ASCII 10/13)

    // sequence as it is needed by the windows edit control. 

    virtual void AddText( LPCWSTR pwszAdd, bool bLFtoCRLF = false );
    // Converts pszAdd to UNICODE and calls the above

    void AddText( LPCSTR pszAdd, bool bLFtoCRLF = false );

    // Sets the edit-control to be used for logging.

    // Pass NULL to stop text logging.

    virtual void SetEditCtrl( HWND hEdit );

    HWND GetEditCtrl() const


The sample project

The included sample project shows the usage of CEditLog and how to use basic_editstrbuf to redirect std::cout to use the edit log.

CEditLog uses the CSubclassWnd class, written by William E. Kempf for implementation. I have included the soure of CSubclassWnd in the sample project, the complete article is also available here at CodeProject.


1.0First Release
1.1Minor Revision. Now uses V2.0 of SubclassWindow.
Now really works on Win9x (V1.0 used UNICODE for internal data handling and failed on Win9x systems. Now the code checks if it runs on Win9x and does the required conversions.)
1.2Minor Revision. Now compiles fine even in VC.NET 2003.


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


About the Author

Daniel Lohmann
Germany Germany
Daniel Lohmann ( is Assistant Professor at the Distributed Systems and Operating Systems department at Friedrich-Alexander-University Erlangen-Nuremberg, Germany. His main research topic is the design of a highly customizable and scalable operating system product line for deeply embedded systems using static configuration and aspect-oriented techniques. Before joining Universität Erlangen he worked as a freelance trainer and consultant for NT system programming, advanced C++ programming and OOA/OOD. He is interested in upcoming programming techniques like aspect-oriented programming, generative programming and C++ meta coding and has written some nice and handy tools for Windows NT which you can download at his web site.

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Comments and Discussions

Questionhow I can add color to ceditlog? Pin
Member 328166623-Apr-13 5:18
memberMember 328166623-Apr-13 5:18 
GeneralPassed on compiling, but failed on running on Windows Vista Pin
Golden Lee3-Dec-09 19:25
memberGolden Lee3-Dec-09 19:25 
GeneralRe: Passed on compiling, but failed on running on Windows Vista Pin
Daniel Lohmann7-Dec-09 0:37
memberDaniel Lohmann7-Dec-09 0:37 
AnswerRe: Passed on compiling, but failed on running on Windows Vista Pin
ysliou19-May-11 3:53
memberysliou19-May-11 3:53 
GeneralRe: Passed on compiling, but failed on running on Windows Vista Pin
Randor 7-Jul-12 13:50
professional Randor 7-Jul-12 13:50 
GeneralRe: Passed on compiling, but failed on running on Windows Vista Pin
Walter Schmoll19-Sep-12 22:40
memberWalter Schmoll19-Sep-12 22:40 
GeneralRe: Passed on compiling, but failed on running on Windows Vista Pin
Randor 17-Oct-12 14:09
professional Randor 17-Oct-12 14:09 
QuestionHow can I change the text color in this Class Pin
huyphuc9-Dec-08 15:42
memberhuyphuc9-Dec-08 15:42 
QuestionHow do i use it for CRichEditCtrl? Pin
smalti16-Aug-07 3:02
membersmalti16-Aug-07 3:02 
GeneralMax. number of lines control Pin
Vic Siu7-Oct-06 15:59
memberVic Siu7-Oct-06 15:59 
QuestionWhat about printf Pin
Avri27-Sep-06 19:54
memberAvri27-Sep-06 19:54 
AnswerRe: What about printf Pin
nikestone24-Nov-06 17:31
membernikestone24-Nov-06 17:31 
GeneralNice but some error in VC2005 Pin
ansoncat13-Jun-06 19:02
memberansoncat13-Jun-06 19:02 
GeneralRe: Nice but some error in VC2005 Pin
w00tzenheimer21-Jul-06 19:39
memberw00tzenheimer21-Jul-06 19:39 
GeneralNice Pin
ucc8012-Feb-06 23:03
memberucc8012-Feb-06 23:03 
GeneralSlow log Pin
vdaanen25-Nov-05 1:26
membervdaanen25-Nov-05 1:26 
GeneralRe: Slow log Pin
Daniel Lohmann26-Nov-05 3:28
memberDaniel Lohmann26-Nov-05 3:28 
QuestionApplication Crash on exit Pin
Prof.S.Mukherjee13-Nov-05 20:47
memberProf.S.Mukherjee13-Nov-05 20:47 
AnswerRe: Application Crash on exit Pin
churl-hee Jo9-May-06 18:29
memberchurl-hee Jo9-May-06 18:29 
QuestionHow to change font Pin
Member 115045313-Jul-05 1:38
memberMember 115045313-Jul-05 1:38 
AnswerRe: How to change font Pin
Daniel Lohmann13-Jul-05 22:24
memberDaniel Lohmann13-Jul-05 22:24 
GeneralRe: How to change font Pin
Member 115045314-Jul-05 23:42
memberMember 115045314-Jul-05 23:42 
Generalx64 (AMD64) portability problem Pin
ModMa28-Jun-05 6:36
memberModMa28-Jun-05 6:36 
AnswerRe: x64 (AMD64) portability problem Pin
pc_jisakker5-Apr-09 5:19
memberpc_jisakker5-Apr-09 5:19 
GeneralVery Good Pin
Iain Fraser / Zeus9-May-05 4:21
memberIain Fraser / Zeus9-May-05 4:21 

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