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 {\it 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, they come in different kinds:
  70
  71 \begin{itemize}\itemsep=0pt
  72 \item{wxTraceMemAlloc} for the messages about creating and deleting objects
  73 \item{wxTraceMessages} for tracing the windowing system messages/events
  74 \item{wxTraceResAlloc} for allocating and releasing the system ressources
  75 \item{wxTraceRefCount} for reference counting related messages
  76 \item{wxTraceOleCalls} for the OLE (or COM) method invocations (wxMSW only)
  77 \item{other} the remaining bits are free for user-defined trace levels
  78 \end{itemize}
  79
  80 The trace mask is a bit mask which tells which (if any) of these trace
  81 messages are going to be actually logged. For the trace message to appear
  82 somewhere, all the bits in the mask used in the call to {\it wxLogTrace()}
  83 function must be set in the current trace mask. For example,
  84 \begin{verbatim}
  85 wxLogTrace(wxTraceRefCount | wxTraceOle, "Active object ref count: %d", nRef);
  86 \end{verbatim}
  87 will do something only if the current trace mask contains both wxTraceRefCount
  88 and wxTraceOle.
  89
  90 Finally, the {\it wxLog::DoLog()} function automatically prepends a time stamp
  91 to all the messages. The format of the time stamp may be changed: it can be
  92 any string with \% specificators fully described in the documentation of the
  93 standard {\it strftime()} function. For example, the default format is
  94 "[\%d/\%b/\%y \%H:\%M:\%S] " which gives something like "[17/Sep/98 22:10:16] "
  95 (without quotes) for the current date. Setting an empty string as the time
  96 format disables timestamping of the messages completely.
  97
  98 \helpref{SetVerbose}{wxlogsetverbose}\\
  99 \helpref{GetVerbose}{wxloggetverbose}\\
 100 \helpref{SetTimestamp}{wxlogsettimestamp}\\
 101 \helpref{GetTimestamp}{wxloggettimestamp}\\
 102 \helpref{SetTraceMask}{wxlogsettracemask}\\
 103 \helpref{GetTraceMask}{wxloggettracemask}
 104
 105 %%%%% MEMBERS HERE %%%%%
 106 \helponly{\insertatlevel{2}{
 107
 108 \wxheading{Members}
 109
 110 }}
 111
 112 \membersection{wxLog::OnLog}\label{wxlogonlog}
 113
 114 \func{static void}{OnLog}{\param{wxLogLevel }{ level}, \param{const char * }{ message}}
 115
 116 Forwards the message at specified level to the {\it DoLog()} function of the
 117 active log target if there is any, does nothing otherwise.
 118
 119 \membersection{wxLog::GetActiveTarget}\label{wxloggetactivetarget}
 120
 121 \func{static wxLog *}{GetActiveTarget}{\void}
 122
 123 Returns the pointer to the active log target (may be NULL).
 124
 125 \membersection{wxLog::SetActiveTarget}\label{wxlogsetactivetarget}
 126
 127 \func{static wxLog *}{SetActiveTarget}{\param{wxLog * }{ logtarget}}
 128
 129 Sets the specified log target as the active one. Returns the pointer to the
 130 previous active log target (may be NULL).
 131
 132 \membersection{wxLog::DontCreateOnDemand}\label{wxlogdontcreateondemand}
 133
 134 \func{static void}{DontCreateOnDemand}{\void}
 135
 136 Instructs wxLog to not create new log targets on the fly if there is none
 137 currently. (Almost) for internal use only.
 138
 139 \membersection{wxLog::Flush}\label{wxlogflush}
 140
 141 \func{virtual void}{Flush}{\void}
 142
 143 Shows all the messages currently in buffer and clears it. If the buffer
 144 is already empty, nothing happens.
 145
 146 \membersection{wxLog::FlushActive}\label{wxlogflushactive}
 147
 148 \func{static void}{FlushActive}{\void}
 149
 150 Flushes the current log target if any, does nothing if there is none.
 151
 152 See also:
 153
 154 \helpref{Flush}{wxlogflush}
 155
 156 \membersection{wxLog::HasPendingMessages}\label{haspendingmessages}
 157
 158 \constfunc{bool}{HasPendingMessages}{\void}
 159
 160 Returns true if there are any messages in the buffer (not yet shown to the
 161 user). (Almost) for internal use only.
 162
 163 \membersection{wxLog::SetVerbose}\label{wxlogsetverbose}
 164
 165 \func{void}{SetVerbose}{\param{bool }{ verbose = TRUE}}
 166
 167 Activates or desactivates verbose mode in which the verbose messages are
 168 logged as the normal ones instead of being silently dropped.
 169
 170 \membersection{wxLog::GetVerbose}\label{wxloggetverbose}
 171
 172 \constfunc{bool}{GetVerbose}{\void}
 173
 174 Returns whether the verbose mode is currently active.
 175
 176 \membersection{wxLog::SetTimestamp}\label{wxlogsettimestamp}
 177
 178 \func{void}{SetTimestamp}{\param{const char * }{ format}}
 179
 180 Sets the timestamp format prepended by the default log targets to all
 181 messages. The string may contain any normal characters as well as \%
 182 prefixed format specificators, see {\it strftime()} manual for details.
 183 Passing a NULL value (not empty string) to this function disables message timestamping.
 184
 185 \membersection{wxLog::GetTimestamp}\label{wxloggettimestamp}
 186
 187 \constfunc{const char *}{GetTimestamp}{\void}
 188
 189 Returns the current timestamp format string.
 190
 191 \membersection{wxLog::SetTraceMask}\label{wxlogsettracemask}
 192
 193 \func{static void}{SetTraceMask}{\param{wxTraceMask }{ mask}}
 194
 195 Sets the trace mask, see \helpref{Customization}{wxlogcustomization}
 196 section for details.
 197
 198 \membersection{wxLog::GetTraceMask}\label{wxloggettracemask}
 199
 200 Returns the current trace mask, see \helpref{Customization}{wxlogcustomization} section
 201 for details.
 202