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,
  34 \helpref{DontCreateOnDemand()}{wxlogdontcreateondemand}
  35 disables the automatic creation of a standard log target
  36 if none actually exists. It is only useful when the application is terminating
  37 and shouldn't be used in other situations because it may easily lead to a loss
  38 of messages.
  39
  40 \helpref{OnLog}{wxlogonlog}\\
  41 \helpref{GetActiveTarget}{wxloggetactivetarget}\\
  42 \helpref{SetActiveTarget}{wxlogsetactivetarget}\\
  43 \helpref{DontCreateOnDemand}{wxlogdontcreateondemand}
  44
  45 \membersection{Message buffering}
  46
  47 Some of wxLog implementations, most notably the standard
  48 wxLogGui class, buffer the messages (for example, to avoid
  49 showing the user a zillion of modal message boxes one after another - which
  50 would be really annoying). {\it Flush()} shows them all and clears the buffer
  51 contents. Although this function doesn't do anything if the buffer is already
  52 empty, {\it HasPendingMessages()} is also provided which allows to explicitly
  53 verify it.
  54
  55 \helpref{Flush}{wxlogflush}\\
  56 \helpref{FlushActive}{wxlogflushactive}\\
  57 \helpref{HasPendingMessages}{haspendingmessages}
  58
  59 \membersection{Customization}\label{wxlogcustomization}
  60
  61 The functions below allow some limited customization of wxLog behaviour
  62 without writing a new log target class (which, aside of being a matter of
  63 several minutes, allows you to do anything you want).
  64
  65 The verbose messages are the trace messages which are not disabled in the
  66 release mode and are generated by \helpref{wxLogVerbose}{wxlogverbose}. They
  67 are not normally shown to the user because they present little interest, but
  68 may be activated, for example, in order to help the user find some program
  69 problem.
  70
  71 As for the (real) trace messages, their handling depends on the settings of
  72 the (application global) {\it trace mask}. There are two ways to specify it:
  73 either by using \helpref{SetTraceMask}{wxlogsettracemask} and
  74 \helpref{GetTraceMask}{wxloggettracemask} and using
  75 \helpref{wxLogTrace}{wxlogtrace} which takes an integer mask or by using
  76 \helpref{AddTraceMask}{wxlogaddtracemask} for string trace masks.
  77
  78 The difference between bit-wise and string trace masks is that a message using
  79 integer trace mask will only be logged if all bits of the mask are set in the
  80 current mask while a message using string mask will be logged simply if the
  81 mask had been added before to the list of allowed ones.
  82
  83 For example,
  84
  85 \begin{verbatim}
  86 // wxTraceOleCalls is one of standard bit masks
  87 wxLogTrace(wxTraceRefCount | wxTraceOleCalls, "Active object ref count: %d", nRef);
  88 \end{verbatim}
  89 will do something only if the current trace mask contains both
  90 {\tt wxTraceRefCount} and {\tt wxTraceOle}, but
  91
  92 \begin{verbatim}
  93 // wxTRACE_OleCalls is one of standard string masks
  94 wxLogTrace(wxTRACE_OleCalls, "IFoo::Bar() called");
  95 \end{verbatim}
  96
  97 will log the message if it was preceded by
  98
  99 \begin{verbatim}
 100 wxLog::AddTraceMask(wxTRACE_OleCalls);
 101 \end{verbatim}
 102
 103 Using string masks is simpler and allows to easily add custom ones, so this is
 104 the preferred way of working with trace messages. The integer trace mask is
 105 kept for compatibility and for additional (but very rarely needed) flexibility
 106 only.
 107
 108 The standard trace masks are given in \helpref{wxLogTrace}{wxlogtrace}
 109 documentation.
 110
 111 Finally, the {\it wxLog::DoLog()} function automatically prepends a time stamp
 112 to all the messages. The format of the time stamp may be changed: it can be
 113 any string with \% specificators fully described in the documentation of the
 114 standard {\it strftime()} function. For example, the default format is
 115 "[\%d/\%b/\%y \%H:\%M:\%S] " which gives something like "[17/Sep/98 22:10:16] "
 116 (without quotes) for the current date. Setting an empty string as the time
 117 format disables timestamping of the messages completely.
 118
 119 {\bf NB:} Timestamping is disabled for Visual C++ users in debug builds by
 120 default because otherwise it would be impossible to directly go to the line
 121 from which the log message was generated by simply clicking in the debugger
 122 window on the corresponding error message. If you wish to enable it, please use
 123 \helpref{SetTimestamp}{wxlogsettimestamp} explicitly.
 124
 125 \helpref{AddTraceMask}{wxlogaddtracemask}\\
 126 \helpref{RemoveTraceMask}{wxlogremovetracemask}\\
 127 \helpref{ClearTraceMasks}{wxlogcleartracemasks}\\
 128 \helpref{IsAllowedTraceMask}{wxlogisallowedtracemask}\\
 129 \helpref{SetVerbose}{wxlogsetverbose}\\
 130 \helpref{GetVerbose}{wxloggetverbose}\\
 131 \helpref{SetTimestamp}{wxlogsettimestamp}\\
 132 \helpref{GetTimestamp}{wxloggettimestamp}\\
 133 \helpref{SetTraceMask}{wxlogsettracemask}\\
 134 \helpref{GetTraceMask}{wxloggettracemask}
 135
 136 %%%%% MEMBERS HERE %%%%%
 137 \helponly{\insertatlevel{2}{
 138
 139 \wxheading{Members}
 140
 141 }}
 142
 143 \membersection{wxLog::AddTraceMask}\label{wxlogaddtracemask}
 144
 145 \func{static void}{AddTraceMask}{\param{const wxString\& }{mask}}
 146
 147 Add the {\it mask} to the list of allowed masks for
 148 \helpref{wxLogTrace}{wxlogtrace}.
 149
 150 See also: \helpref{RemoveTraceMask}{wxlogremovetracemask}
 151
 152 \membersection{wxLog::ClearTraceMasks}\label{wxlogcleartracemasks}
 153
 154 \func{static void}{ClearTraceMasks}{\void}
 155
 156 Removes all trace masks previously set with
 157 \helpref{AddTraceMask}{wxlogaddtracemask}.
 158
 159 See also: \helpref{RemoveTraceMask}{wxlogremovetracemask}
 160
 161 \membersection{wxLog::OnLog}\label{wxlogonlog}
 162
 163 \func{static void}{OnLog}{\param{wxLogLevel }{ level}, \param{const char * }{ message}}
 164
 165 Forwards the message at specified level to the {\it DoLog()} function of the
 166 active log target if there is any, does nothing otherwise.
 167
 168 \membersection{wxLog::GetActiveTarget}\label{wxloggetactivetarget}
 169
 170 \func{static wxLog *}{GetActiveTarget}{\void}
 171
 172 Returns the pointer to the active log target (may be NULL).
 173
 174 \membersection{wxLog::SetActiveTarget}\label{wxlogsetactivetarget}
 175
 176 \func{static wxLog *}{SetActiveTarget}{\param{wxLog * }{ logtarget}}
 177
 178 Sets the specified log target as the active one. Returns the pointer to the
 179 previous active log target (may be NULL).
 180
 181 \membersection{wxLog::DontCreateOnDemand}\label{wxlogdontcreateondemand}
 182
 183 \func{static void}{DontCreateOnDemand}{\void}
 184
 185 Instructs wxLog to not create new log targets on the fly if there is none
 186 currently. (Almost) for internal use only: it is supposed to be called by the
 187 application shutdown code.
 188
 189 Note that this function also calls
 190 \helpref{ClearTraceMasks}{wxlogcleartracemasks}.
 191
 192 \membersection{wxLog::Flush}\label{wxlogflush}
 193
 194 \func{virtual void}{Flush}{\void}
 195
 196 Shows all the messages currently in buffer and clears it. If the buffer
 197 is already empty, nothing happens.
 198
 199 \membersection{wxLog::FlushActive}\label{wxlogflushactive}
 200
 201 \func{static void}{FlushActive}{\void}
 202
 203 Flushes the current log target if any, does nothing if there is none.
 204
 205 See also:
 206
 207 \helpref{Flush}{wxlogflush}
 208
 209 \membersection{wxLog::HasPendingMessages}\label{haspendingmessages}
 210
 211 \constfunc{bool}{HasPendingMessages}{\void}
 212
 213 Returns true if there are any messages in the buffer (not yet shown to the
 214 user). (Almost) for internal use only.
 215
 216 \membersection{wxLog::SetVerbose}\label{wxlogsetverbose}
 217
 218 \func{void}{SetVerbose}{\param{bool }{ verbose = TRUE}}
 219
 220 Activates or desactivates verbose mode in which the verbose messages are
 221 logged as the normal ones instead of being silently dropped.
 222
 223 \membersection{wxLog::GetVerbose}\label{wxloggetverbose}
 224
 225 \constfunc{bool}{GetVerbose}{\void}
 226
 227 Returns whether the verbose mode is currently active.
 228
 229 \membersection{wxLog::SetTimestamp}\label{wxlogsettimestamp}
 230
 231 \func{void}{SetTimestamp}{\param{const char * }{ format}}
 232
 233 Sets the timestamp format prepended by the default log targets to all
 234 messages. The string may contain any normal characters as well as \%
 235 prefixed format specificators, see {\it strftime()} manual for details.
 236 Passing a NULL value (not empty string) to this function disables message timestamping.
 237
 238 \membersection{wxLog::GetTimestamp}\label{wxloggettimestamp}
 239
 240 \constfunc{const char *}{GetTimestamp}{\void}
 241
 242 Returns the current timestamp format string.
 243
 244 \membersection{wxLog::SetTraceMask}\label{wxlogsettracemask}
 245
 246 \func{static void}{SetTraceMask}{\param{wxTraceMask }{ mask}}
 247
 248 Sets the trace mask, see \helpref{Customization}{wxlogcustomization}
 249 section for details.
 250
 251 \membersection{wxLog::GetTraceMask}\label{wxloggettracemask}
 252
 253 Returns the current trace mask, see \helpref{Customization}{wxlogcustomization} section
 254 for details.
 255
 256 \membersection{wxLog::IsAllowedTraceMask}\label{wxlogisallowedtracemask}
 257
 258 \func{static bool}{IsAllowedTraceMask}{\param{const wxChar *}{mask}}
 259
 260 Returns TRUE if the {\it mask} is one of allowed masks for
 261 \helpref{wxLogTrace}{wxlogtrace}.
 262
 263 See also: \helpref{AddTraceMask}{wxlogaddtracemask},
 264 \helpref{RemoveTraceMask}{wxlogremovetracemask}
 265
 266 \membersection{wxLog::RemoveTraceMask}\label{wxlogremovetracemask}
 267
 268 \func{static void}{RemoveTraceMask}{\param{const wxString\& }{mask}}
 269
 270 Remove the {\it mask} from the list of allowed masks for
 271 \helpref{wxLogTrace}{wxlogtrace}.
 272
 273 See also: \helpref{AddTraceMask}{wxlogaddtracemask}
 274