docs/latex/wx/log.tex

   1 \section{\class{wxLog}}\label{wxlog}
   2
   3 wxLog class defines the interface for the {\it log targets} used by wxWindows
   4 logging functions as explained in the \helpref{wxLog overview}{wxlogoverview}.
   5 The only situations when you need to directly use this class is when you want
   6 to derive your own log target because the existing ones don't satisfy your
   7 needs. Another case is if you wish to customize the behaviour of the standard
   8 logging classes (all of which respect the wxLog settings): for example, set
   9 which trace messages are logged and which are not or change (or even remove
  10 completely) the timestamp on the messages.
  11
  12 Otherwise, it is completely hidden behind the {\it wxLogXXX()} functions and
  13 you may not even know about its existence.
  14
  15 See \helpref{log overview}{wxlogoverview} for the descriptions of wxWindows
  16 logging facilities.
  17
  18 \wxheading{Derived from}
  19
  20 No base class
  21
  22 \wxheading{Include files}
  23
  24 <wx/log.h>
  25
  26 \latexignore{\rtfignore{\wxheading{Function groups}}}
  27
  28 \membersection{Static functions}
  29
  30 The functions in this section work with and manipulate the active log target.
  31 The {\it OnLog()} is called by the {\it wxLogXXX()} functions and invokes the
  32 {\it DoLog()} of the active log target if any. Get/Set methods are used to
  33 install/query the current active target and, finally, {\it
  34 DontCreateOnDemand()} disables the automatic creation of a standard log target
  35 if none actually exists. It is only useful when the application is terminating
  36 and shouldn't be used in other situations because it may easily lead to a loss
  37 of messages.
  38
  39 \helpref{OnLog}{wxlogonlog}\\
  40 \helpref{GetActiveTarget}{wxloggetactivetarget}\\
  41 \helpref{SetActiveTarget}{wxlogsetactivetarget}\\
  42 \helpref{DontCreateOnDemand}{wxlogdontcreateondemand}
  43
  44 \membersection{Message buffering}
  45
  46 Some of wxLog implementations, most notably the standard
  47 wxLogGui class, buffer the messages (for example, to avoid
  48 showing the user a zillion of modal message boxes one after another - which
  49 would be really annoying). {\it Flush()} shows them all and clears the buffer
  50 contents. Although this function doesn't do anything if the buffer is already
  51 empty, {\it HasPendingMessages()} is also provided which allows to explicitly
  52 verify it.
  53
  54 \helpref{Flush}{wxlogflush}\\
  55 \helpref{FlushActive}{wxlogflushactive}\\
  56 \helpref{HasPendingMessages}{haspendingmessages}
  57
  58 \membersection{Customization}\label{wxlogcustomization}
  59
  60 The functions below allow some limited customization of wxLog behaviour
  61 without writing a new log target class (which, aside of being a matter of
  62 several minutes, allows you to do anything you want).
  63
  64 The verbose messages are the trace messages which are not disabled in the
  65 release mode and are generated by \helpref{wxLogVerbose}{wxlogverbose}. They
  66 are not normally shown to the user because they present little interest, but
  67 may be activated, for example, in order to help the user find some program
  68 problem.
  69
  70 As for the (real) trace messages, their handling depends on the settings of
  71 the (application global) {\it trace mask}. There are two ways to specify it:
  72 either by using \helpref{SetTraceMask}{wxlogsettracemask} and
  73 \helpref{GetTraceMask}{wxloggettracemask} and using
  74 \helpref{wxLogTrace}{wxlogtrace} which takes an integer mask or by using
  75 \helpref{AddTraceMask}{wxlogaddtracemask} for string trace masks.
  76
  77 The difference between bit-wise and string trace masks is that a message using
  78 integer trace mask will only be logged if all bits of the mask are set in the
  79 current mask while a message using string mask will be logged simply if the
  80 mask had been added before to the list of allowed ones.
  81
  82 For example,
  83 \begin{verbatim}
  84 // wxTraceOleCalls is one of standard bit masks
  85 wxLogTrace(wxTraceRefCount | wxTraceOleCalls, "Active object ref count: %d", nRef);
  86 \end{verbatim}
  87 will do something only if the current trace mask contains both
  88 {\tt wxTraceRefCount} and {\tt wxTraceOle}, but
  89 \begin{verbatim}
  90 // wxTRACE_OleCalls is one of standard string masks
  91 wxLogTrace(wxTRACE_OleCalls, "IFoo::Bar() called");
  92 \end{verbatim}
  93 will log the message if it was preceded by
  94 \begin{verbatim}
  95 wxLog::AddTraceMask(wxTRACE_OleCalls);
  96 \end{verbatim}
  97
  98 Using string masks is simpler and allows to easily add custom ones, so this is
  99 the preferred way of working with trace messages. The integer trace mask is
 100 kept for compatibility and for additional (but very rarely needed) flexibility
 101 only.
 102
 103 The standard trace masks are given in \helpref{wxLogTrace}{wxlogtrace}
 104 documentation.
 105
 106 Finally, the {\it wxLog::DoLog()} function automatically prepends a time stamp
 107 to all the messages. The format of the time stamp may be changed: it can be
 108 any string with \% specificators fully described in the documentation of the
 109 standard {\it strftime()} function. For example, the default format is
 110 "[\%d/\%b/\%y \%H:\%M:\%S] " which gives something like "[17/Sep/98 22:10:16] "
 111 (without quotes) for the current date. Setting an empty string as the time
 112 format disables timestamping of the messages completely.
 113
 114 {\bf NB:} Timestamping is disabled for Visual C++ users in debug builds by
 115 default because otherwise it would be impossible to directly go to the line
 116 from which the log message was generated by simply clicking in the debugger
 117 window on the corresponding error message. If you wish to enable it, please use
 118 \helpref{SetTimestamp}{wxlogsettimestamp} explicitly.
 119
 120 \helpref{AddTraceMask}{wxlogaddtracemask}\\
 121 \helpref{RemoveTraceMask}{wxlogremovetracemask}\\
 122 \helpref{IsAllowedTraceMask}{wxlogisallowedtracemask}\\
 123 \helpref{SetVerbose}{wxlogsetverbose}\\
 124 \helpref{GetVerbose}{wxloggetverbose}\\
 125 \helpref{SetTimestamp}{wxlogsettimestamp}\\
 126 \helpref{GetTimestamp}{wxloggettimestamp}\\
 127 \helpref{SetTraceMask}{wxlogsettracemask}\\
 128 \helpref{GetTraceMask}{wxloggettracemask}
 129
 130 %%%%% MEMBERS HERE %%%%%
 131 \helponly{\insertatlevel{2}{
 132
 133 \wxheading{Members}
 134
 135 }}
 136
 137 \membersection{wxLog::AddTraceMask}\label{wxlogaddtracemask}
 138
 139 \func{static void}{AddTraceMask}{\param{const wxString\& }{mask}}
 140
 141 Add the {\it mask} to the list of allowed masks for
 142 \helpref{wxLogTrace}{wxlogtrace}.
 143
 144 See also: \helpref{RemoveTraceMask}{wxlogremovetracemask}
 145
 146 \membersection{wxLog::OnLog}\label{wxlogonlog}
 147
 148 \func{static void}{OnLog}{\param{wxLogLevel }{ level}, \param{const char * }{ message}}
 149
 150 Forwards the message at specified level to the {\it DoLog()} function of the
 151 active log target if there is any, does nothing otherwise.
 152
 153 \membersection{wxLog::GetActiveTarget}\label{wxloggetactivetarget}
 154
 155 \func{static wxLog *}{GetActiveTarget}{\void}
 156
 157 Returns the pointer to the active log target (may be NULL).
 158
 159 \membersection{wxLog::SetActiveTarget}\label{wxlogsetactivetarget}
 160
 161 \func{static wxLog *}{SetActiveTarget}{\param{wxLog * }{ logtarget}}
 162
 163 Sets the specified log target as the active one. Returns the pointer to the
 164 previous active log target (may be NULL).
 165
 166 \membersection{wxLog::DontCreateOnDemand}\label{wxlogdontcreateondemand}
 167
 168 \func{static void}{DontCreateOnDemand}{\void}
 169
 170 Instructs wxLog to not create new log targets on the fly if there is none
 171 currently. (Almost) for internal use only.
 172
 173 \membersection{wxLog::Flush}\label{wxlogflush}
 174
 175 \func{virtual void}{Flush}{\void}
 176
 177 Shows all the messages currently in buffer and clears it. If the buffer
 178 is already empty, nothing happens.
 179
 180 \membersection{wxLog::FlushActive}\label{wxlogflushactive}
 181
 182 \func{static void}{FlushActive}{\void}
 183
 184 Flushes the current log target if any, does nothing if there is none.
 185
 186 See also:
 187
 188 \helpref{Flush}{wxlogflush}
 189
 190 \membersection{wxLog::HasPendingMessages}\label{haspendingmessages}
 191
 192 \constfunc{bool}{HasPendingMessages}{\void}
 193
 194 Returns true if there are any messages in the buffer (not yet shown to the
 195 user). (Almost) for internal use only.
 196
 197 \membersection{wxLog::SetVerbose}\label{wxlogsetverbose}
 198
 199 \func{void}{SetVerbose}{\param{bool }{ verbose = TRUE}}
 200
 201 Activates or desactivates verbose mode in which the verbose messages are
 202 logged as the normal ones instead of being silently dropped.
 203
 204 \membersection{wxLog::GetVerbose}\label{wxloggetverbose}
 205
 206 \constfunc{bool}{GetVerbose}{\void}
 207
 208 Returns whether the verbose mode is currently active.
 209
 210 \membersection{wxLog::SetTimestamp}\label{wxlogsettimestamp}
 211
 212 \func{void}{SetTimestamp}{\param{const char * }{ format}}
 213
 214 Sets the timestamp format prepended by the default log targets to all
 215 messages. The string may contain any normal characters as well as \%
 216 prefixed format specificators, see {\it strftime()} manual for details.
 217 Passing a NULL value (not empty string) to this function disables message timestamping.
 218
 219 \membersection{wxLog::GetTimestamp}\label{wxloggettimestamp}
 220
 221 \constfunc{const char *}{GetTimestamp}{\void}
 222
 223 Returns the current timestamp format string.
 224
 225 \membersection{wxLog::SetTraceMask}\label{wxlogsettracemask}
 226
 227 \func{static void}{SetTraceMask}{\param{wxTraceMask }{ mask}}
 228
 229 Sets the trace mask, see \helpref{Customization}{wxlogcustomization}
 230 section for details.
 231
 232 \membersection{wxLog::GetTraceMask}\label{wxloggettracemask}
 233
 234 Returns the current trace mask, see \helpref{Customization}{wxlogcustomization} section
 235 for details.
 236
 237 \membersection{wxLog::IsAllowedTraceMask}\label{wxlogisallowedtracemask}
 238
 239 \func{static bool}{IsAllowedTraceMask}{\param{const wxChar *}{mask}}
 240
 241 Returns TRUE if the {\it mask} is one of allowed masks for
 242 \helpref{wxLogTrace}{wxlogtrace}.
 243
 244 See also: \helpref{AddTraceMask}{wxlogaddtracemask},
 245 \helpref{RemoveTraceMask}{wxlogremovetracemask}
 246
 247 \membersection{wxLog::RemoveTraceMask}\label{wxlogremovetracemask}
 248
 249 \func{static void}{RemoveTraceMask}{\param{const wxString\& }{mask}}
 250
 251 Remove the {\it mask} from the list of allowed masks for
 252 \helpref{wxLogTrace}{wxlogtrace}.
 253
 254 See also: \helpref{AddTraceMask}{wxlogaddtracemask}
 255