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 \latexignore{\rtfignore{\wxheading{Function groups}}}
  23
  24 \membersection{Static functions}
  25
  26 The functions in this section work with and manipulate the active log target.
  27 The {\it OnLog()} is called by the {\it wxLogXXX()} functions and invokes the
  28 {\it DoLog()} of the active log target if any. Get/Set methods are used to
  29 install/query the current active target and, finally, {\it
  30 DontCreateOnDemand()} disables the automatic creation of a standard log target
  31 if none actually exists. It is only useful when the application is terminating
  32 and shouldn't be used in other situations because it may easily lead to a loss
  33 of messages.
  34
  35 \helpref{OnLog}{wxlogonlog}\\
  36 \helpref{GetActiveTarget}{wxloggetactivetarget}\\
  37 \helpref{SetActiveTarget}{wxlogsetactivetarget}\\
  38 \helpref{DontCreateOnDemand}{wxlogdontcreateondemand}
  39
  40 \membersection{Message buffering}
  41
  42 Some of wxLog implementations, most notably the standard
  43 wxLogGui class, buffer the messages (for example, to avoid
  44 showing the user a zillion of modal message boxes one after another - which
  45 would be really annoying). {\it Flush()} shows them all and clears the buffer
  46 contents. Although this function doesn't do anything if the buffer is already
  47 empty, {\it HasPendingMessages()} is also provided which allows to explicitly
  48 verify it.
  49
  50 \helpref{Flush}{wxlogflush}\\
  51 \helpref{HasPendingMessages}{haspendingmessages}
  52
  53 \membersection{Customization}\label{wxlogcustomization}
  54
  55 The functions below allow some limited customization of wxLog behaviour
  56 without writing a new log target class (which, aside of being a matter of
  57 several minutes, allows you to do anything you want).
  58
  59 The verbose messages are the trace messages which are not disabled in the
  60 release mode and are generated by {\it wxLogVerbose()}. They are not normally
  61 shown to the user because they present little interest, but may be activated,
  62 for example, in order to help the user find some program problem.
  63
  64 As for the (real) trace messages, they come in different kinds:
  65
  66 \begin{itemize}\itemsep=0pt
  67 \item{wxTraceMemAlloc} for the messages about creating and deleting objects
  68 \item{wxTraceMessages} for tracing the windowing system messages/events
  69 \item{wxTraceResAlloc} for allocating and releasing the system ressources
  70 \item{wxTraceRefCount} for reference counting related messages
  71 \item{wxTraceOleCalls} for the OLE (or COM) method invocations (wxMSW only)
  72 \item{other} the remaining bits are free for user-defined trace levels
  73 \end{itemize}
  74
  75 The trace mask is a bit mask which tells which (if any) of these trace
  76 messages are going to be actually logged. For the trace message to appear
  77 somewhere, all the bits in the mask used in the call to {\it wxLogTrace()}
  78 function must be set in the current trace mask. For example,
  79 \begin{verbatim}
  80 wxLogTrace(wxTraceRefCount | wxTraceOle, "Active object ref count: %d", nRef);
  81 \end{verbatim}
  82 will do something only if the current trace mask contains both wxTraceRefCount
  83 and wxTraceOle.
  84
  85 Finally, the {\it wxLog::DoLog()} function automatically prepends a time stamp
  86 to all the messages. The format of the time stamp may be changed: it can be
  87 any string with \% specificators fully described in the documentation of the
  88 standard {\it strftime()} function. For example, the default format is
  89 "[\%d/\%b/\%y \%H:\%M:\%S] " which gives something like "[17/Sep/98 22:10:16] "
  90 (without quotes) for the current date. Setting an empty string as the time
  91 format disables timestamping of the messages completely.
  92
  93 \helpref{SetVerbose}{wxlogsetverbose}\\
  94 \helpref{GetVerbose}{wxloggetverbose}\\
  95 \helpref{SetTimeStampFormat}{wxlogsettimestampformat}\\
  96 \helpref{GetTimeStampFormat}{wxloggettimestampformat}\\
  97 \helpref{SetTraceMask}{wxlogsettracemask}\\
  98 \helpref{GetTraceMask}{wxloggettracemask}
  99
 100 %%%%% MEMBERS HERE %%%%%
 101 \helponly{\insertatlevel{2}{
 102
 103 \wxheading{Members}
 104
 105 }}
 106
 107 \membersection{wxLog::OnLog}\label{wxlogonlog}
 108
 109 \func{static void}{OnLog}{\param{wxLogLevel }{ level}, \param{const char * }{ message}}
 110
 111 Forwards the message at specified level to the {\it DoLog()} function of the
 112 active log target if there is any, does nothing otherwise.
 113
 114 \membersection{wxLog::GetActiveTarget}\label{wxloggetactivetarget}
 115
 116 \func{static wxLog *}{GetActiveTarget}{\void}
 117
 118 Returns the pointer to the active log target (may be NULL).
 119
 120 \membersection{wxLog::SetActiveTarget}\label{wxlogsetactivetarget}
 121
 122 \func{static wxLog *}{SetActiveTarget}{\param{wxLog * }{ logtarget}}
 123
 124 Sets the specified log target as the active one. Returns the pointer to the
 125 previous active log target (may be NULL).
 126
 127 \membersection{wxLog::DontCreateOnDemand}\label{wxlogdontcreateondemand}
 128
 129 \func{static void}{DontCreateOnDemand}{\void}
 130
 131 Instructs wxLog to not create new log targets on the fly if there is none
 132 currently. (Almost) for internal use only.
 133
 134 \membersection{wxLog::Flush}\label{wxlogflush}
 135
 136 \func{virtual void}{Flush}{\void}
 137
 138 Shows all the messages currently in buffer and clears it. If the buffer
 139 is already empty, nothing happens.
 140
 141 \membersection{wxLog::HasPendingMessages}\label{haspendingmessages}
 142
 143 \constfunc{bool}{HasPendingMessages}{\void}
 144
 145 Returns true if there are any messages in the buffer (not yet shown to the
 146 user). (Almost) for internal use only.
 147
 148 \membersection{wxLog::SetVerbose}\label{wxlogsetverbose}
 149
 150 \func{void}{SetVerbose}{\param{bool }{ verbose = TRUE}}
 151
 152 Activates or desactivates verbose mode in which the verbose messages are
 153 logged as the normal ones instead of being silently dropped.
 154
 155 \membersection{wxLog::GetVerbose}\label{wxloggetverbose}
 156
 157 \constfunc{bool}{GetVerbose}{\void}
 158
 159 Returns whether the verbose mode is currently active.
 160
 161 \membersection{wxLog::SetTimeStampFormat}\label{wxlogsettimestampformat}
 162
 163 \func{void}{SetTimeStampFormat}{\param{const char * }{ format}}
 164
 165 Sets the timestamp format prepended by the default log targets to all
 166 messages. The string may contain any normal characters as well as \%
 167 prefixed format specificators, see {\it strftime()} manual for details.
 168 Passing an empty string to this function disables message timestamping.
 169
 170 \membersection{wxLog::GetTimeStampFormat}\label{wxloggettimestampformat}
 171
 172 \constfunc{const char *}{GetTimeStampFormat}{\void}
 173
 174 Returns the current timestamp format string.
 175
 176 \membersection{wxLog::SetTraceMask}\label{wxlogsettracemask}
 177
 178 \func{static void}{SetTraceMask}{\param{wxTraceMask }{ mask}}
 179
 180 Sets the trace mask, see \helpref{Customization}{wxlogcustomization}
 181 section for details.
 182
 183 \membersection{wxLog::GetTraceMask}\label{wxloggettracemask}
 184
 185 Returns the current trace mask, see \helpref{Customization}{wxlogcustomization} section
 186 for details.