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