wxWidgets/include/wx/log.h

/////////////////////////////////////////////////////////////////////////////
// Name:        log.h
// Purpose:     Assorted wxLogXXX functions, and wxLog (sink for logs)
// Author:      Vadim Zeitlin
// Modified by:
// Created:     29/01/98
// RCS-ID:      $Id$
// Copyright:   (c) 1998 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

#ifndef   __LOGH__
#define   __LOGH__

#ifdef    __GNUG__
#pragma interface "log.h"
#endif  //GNU C++

// ----------------------------------------------------------------------------
// derive from this class to redirect (or suppress, or ...) log messages
// normally, only a single instance of this class exists but it's not enforced
//
// ## would ne nice to add a time stamp to log messages
// ----------------------------------------------------------------------------
class WXDLLEXPORT wxLog
{
public:
  enum Level
  {
    FatalError, // program can't continue, abort immediately
    Error,      // a serious error, user must be informed about it
    Warning,    // warning: user is normally informed about but may ignore it
    Message,    // normal message (i.e. normal output of a non GUI app)
    Info,       // informational message (a.k.a. 'Verbose')
    Status,     // informational: might go to the status line of GUI app
    Debug,      // never shown to the user, disabled in release mode
    Trace,      // trace messages are also only enabled in debug mode
    Progress,   // used for progress indicator (not yet)
    User1,      // user defined levels (use with wxLogGeneric(wxLog::User1,...)
    User2,      //
    User3,      //
  };

  // ctor
  wxLog();

  // sink function
  static void OnLog(Level level, const char *szString)
    { if ( ms_pLogger != 0 ) ms_pLogger->DoLog(level, szString); }

  // message buffering
    // flush shows all messages if they're not logged immediately
    // (FILE and iostream logs don't need it, but wxGuiLog does to avoid
    //  showing 17 modal dialogs one after another)
  virtual void Flush();
    // call Flush() only if this function returns true
  bool HasPendingMessages() const { return m_bHasMessages; }

  // only one sink is active at each moment
    // get current log target
  static wxLog *GetActiveTarget();
    // change log target, pLogger = NULL disables logging,
    // returns the previous log target
  static wxLog *SetActiveTarget(wxLog *pLogger);

  // functions controlling the default wxLog behaviour
    // verbose mode is activated by standard command-line '-verbose' option
  static void SetVerbose(bool bVerbose = TRUE) { ms_bVerbose = bVerbose; }
    // sets the format for timestamp prepended by wxLog::DoLog(): it's
    // passed to strftime() function, see it's documentation for details.
    // the string is not copied!
  static void SetTimeStampFormat(const char *szTimeFormat)
    { ms_szTimeFormat = szTimeFormat; }

  // accessors
    // gets the verbose status
  static bool GetVerbose() { return ms_bVerbose; }

  // make dtor virtual for all derived classes
  virtual ~wxLog() { }

protected:
  bool m_bHasMessages;

  // static variables
  // ----------------
  static bool        ms_bVerbose;     // FALSE => ignore LogInfo messages
  static const char *ms_szTimeFormat; // format for strftime()

private:
  // the logging functions that can be overriden
    // default DoLog() prepends the time stamp and a prefix corresponding
    // to the message to szString and then passes it to DoLogString()
  virtual void DoLog(Level level, const char *szString);
    // default DoLogString does nothing but is not pure virtual because if
    // you override DoLog() you might not need it at all
  virtual void DoLogString(const char *szString);
  
  static wxLog *ms_pLogger;       // currently active log sink
  static bool   ms_bInitialized;  // any log targets created?
};

// ----------------------------------------------------------------------------
// "trivial" derivations of wxLog
// ----------------------------------------------------------------------------

// log everything to a "FILE *", stderr by default
class WXDLLEXPORT wxLogStderr : public wxLog
{
public:
  // redirect log output to a FILE
  wxLogStderr(FILE *fp = NULL);

private:
  // implement sink function
  virtual void DoLogString(const char *szString);

  FILE *m_fp;
};

// log everything to an "ostream", cerr by default
class WXDLLEXPORT wxLogStream : public wxLog
{
public:
  // redirect log output to an ostream
  wxLogStream(ostream *ostr = NULL);

protected:
  // implement sink function
  virtual void DoLogString(const char *szString);

  // @@ using ptr here to avoid including <iostream.h> from this file
  ostream *m_ostr;
};

/*
// log everything to a text window (GUI only of course)
class WXDLLEXPORT wxLogTextCtrl : public wxLogStream
{
public:
  // we just create an ostream from wxTextCtrl and use it in base class
  wxLogTextCtrl(wxTextCtrl *pTextCtrl);
 ~wxLogTextCtrl();
};
*/

// ----------------------------------------------------------------------------
// GUI log target, the default one for wxWindows programs
// ----------------------------------------------------------------------------
class WXDLLEXPORT wxLogGui : public wxLog
{
public:
  // ctor
  wxLogGui();

  // show all messages that were logged since the last Flush()
  virtual void Flush();

protected:
  virtual void DoLog(Level level, const char *szString);

  wxArrayString m_aMessages;
  bool          m_bErrors;
};

// ----------------------------------------------------------------------------
// /dev/null log target: suppress logging until this object goes out of scope
// ----------------------------------------------------------------------------

// example of usage:
/*
void Foo() {
  wxFile file;

  // wxFile.Open() normally complains if file can't be opened, we don't want it
  wxLogNull logNo;
  if ( !file.Open("bar") )
    ... process error ourselves ...

  // ~wxLogNull called, old log sink restored
}
*/
class WXDLLEXPORT wxLogNull
{
public:
  // ctor saves old log target, dtor restores it
  wxLogNull() { m_pPrevLogger = wxLog::SetActiveTarget(NULL); }
 ~wxLogNull() { (void)wxLog::SetActiveTarget(m_pPrevLogger);  }

private:
  wxLog *m_pPrevLogger; // old log target
};

// ============================================================================
// global functions
// ============================================================================

// ----------------------------------------------------------------------------
// Log functions should be used by application instead of stdio, iostream &c
// for log messages for easy redirection
// ----------------------------------------------------------------------------

// define wxLog<level>
// -------------------

// NB: all these functions take `wxTString' and not
//     `const wxTString&' because according to C++ standard
//     the first argument to a vararg function can not be
//     an array, function or reference :-(

// the most generic log function
void WXDLLEXPORT wxLogGeneric(wxLog::Level level, wxTString strFormat, ...);

#define DECLARE_LOG_FUNCTION(level)                                 \
        extern void WXDLLEXPORT wxLog##level(wxTString strFormat, ...)

// one function per each level
DECLARE_LOG_FUNCTION(FatalError);
DECLARE_LOG_FUNCTION(Error);
DECLARE_LOG_FUNCTION(Warning);
DECLARE_LOG_FUNCTION(Message);
DECLARE_LOG_FUNCTION(Info);
DECLARE_LOG_FUNCTION(Status);
DECLARE_LOG_FUNCTION(Verbose);

// additional one: as wxLogError, but also logs last system call error code
// and the corresponding error message if available
DECLARE_LOG_FUNCTION(SysError);

// and another one which also takes the error code (for those broken APIs
// that don't set the errno (like registry APIs in Win32))
void WXDLLEXPORT wxLogSysError(long lErrCode, wxTString strFormat, ...);

// debug functions don't translate their arguments
#undef  DECLARE_LOG_FUNCTION
#define DECLARE_LOG_FUNCTION(level)                                 \
        extern void WXDLLEXPORT wxLog##level(const char *szFormat, ...)

DECLARE_LOG_FUNCTION(Debug);
DECLARE_LOG_FUNCTION(Trace);

// are we in 'verbose' mode?
// (note that it's often handy to change this var manually from the
//  debugger, thus enabling/disabling verbose reporting for some
//  parts of the program only)
WXDLLEXPORT_DATA(extern bool) g_bVerbose;

// fwd decl to avoid including iostream.h here
class ostream;

// ----------------------------------------------------------------------------
// get error code/error message from system in a portable way
// ----------------------------------------------------------------------------

// return the last system error code
unsigned long WXDLLEXPORT wxSysErrorCode();
// return the error message for given (or last if 0) error code
const char* WXDLLEXPORT wxSysErrorMsg(unsigned long nErrCode = 0);

// ----------------------------------------------------------------------------
// debug only logging functions: use them with API name and error code
// ----------------------------------------------------------------------------

#ifdef  __DEBUG__
  #define wxLogApiError(api, rc)                                              \
                    wxLogDebug("At %s(%d) '%s' failed with error %lx (%s).",  \
                               __FILE__, __LINE__, api,                       \
                               rc, wxSysErrorMsg(rc))
  #define wxLogLastError(api) wxLogApiError(api, ::GetLastError())
#else   //!debug
  #define wxLogApiError(api, rc)
  #define wxLogLastError(api)
#endif  //debug/!debug

#endif  //__LOGH__