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{HasPendingMessages}{haspendingmessages}
  56
  57 \membersection{Customization}\label{wxlogcustomization}
  58
  59 The functions below allow some limited customization of wxLog behaviour
  60 without writing a new log target class (which, aside of being a matter of
  61 several minutes, allows you to do anything you want).
  62
  63 The verbose messages are the trace messages which are not disabled in the
  64 release mode and are generated by {\it wxLogVerbose()}. They are not normally
  65 shown to the user because they present little interest, but may be activated,
  66 for example, in order to help the user find some program problem.
  67
  68 As for the (real) trace messages, they come in different kinds:
  69
  70 \begin{itemize}\itemsep=0pt
  71 \item{wxTraceMemAlloc} for the messages about creating and deleting objects
  72 \item{wxTraceMessages} for tracing the windowing system messages/events
  73 \item{wxTraceResAlloc} for allocating and releasing the system ressources
  74 \item{wxTraceRefCount} for reference counting related messages
  75 \item{wxTraceOleCalls} for the OLE (or COM) method invocations (wxMSW only)
  76 \item{other} the remaining bits are free for user-defined trace levels
  77 \end{itemize}
  78
  79 The trace mask is a bit mask which tells which (if any) of these trace
  80 messages are going to be actually logged. For the trace message to appear
  81 somewhere, all the bits in the mask used in the call to {\it wxLogTrace()}
  82 function must be set in the current trace mask. For example,
  83 \begin{verbatim}
  84 wxLogTrace(wxTraceRefCount | wxTraceOle, "Active object ref count: %d", nRef);
  85 \end{verbatim}
  86 will do something only if the current trace mask contains both wxTraceRefCount
  87 and wxTraceOle.
  88
  89 Finally, the {\it wxLog::DoLog()} function automatically prepends a time stamp
  90 to all the messages. The format of the time stamp may be changed: it can be
  91 any string with \% specificators fully described in the documentation of the
  92 standard {\it strftime()} function. For example, the default format is
  93 "[\%d/\%b/\%y \%H:\%M:\%S] " which gives something like "[17/Sep/98 22:10:16] "
  94 (without quotes) for the current date. Setting an empty string as the time
  95 format disables timestamping of the messages completely.
  96
  97 \helpref{SetVerbose}{wxlogsetverbose}\\
  98 \helpref{GetVerbose}{wxloggetverbose}\\
  99 \helpref{SetTimestamp}{wxlogsettimestamp}\\
 100 \helpref{GetTimestamp}{wxloggettimestamp}\\
 101 \helpref{SetTraceMask}{wxlogsettracemask}\\
 102 \helpref{GetTraceMask}{wxloggettracemask}
 103
 104 %%%%% MEMBERS HERE %%%%%
 105 \helponly{\insertatlevel{2}{
 106
 107 \wxheading{Members}
 108
 109 }}
 110
 111 \membersection{wxLog::OnLog}\label{wxlogonlog}
 112
 113 \func{static void}{OnLog}{\param{wxLogLevel }{ level}, \param{const char * }{ message}}
 114
 115 Forwards the message at specified level to the {\it DoLog()} function of the
 116 active log target if there is any, does nothing otherwise.
 117
 118 \membersection{wxLog::GetActiveTarget}\label{wxloggetactivetarget}
 119
 120 \func{static wxLog *}{GetActiveTarget}{\void}
 121
 122 Returns the pointer to the active log target (may be NULL).
 123
 124 \membersection{wxLog::SetActiveTarget}\label{wxlogsetactivetarget}
 125
 126 \func{static wxLog *}{SetActiveTarget}{\param{wxLog * }{ logtarget}}
 127
 128 Sets the specified log target as the active one. Returns the pointer to the
 129 previous active log target (may be NULL).
 130
 131 \membersection{wxLog::DontCreateOnDemand}\label{wxlogdontcreateondemand}
 132
 133 \func{static void}{DontCreateOnDemand}{\void}
 134
 135 Instructs wxLog to not create new log targets on the fly if there is none
 136 currently. (Almost) for internal use only.
 137
 138 \membersection{wxLog::Flush}\label{wxlogflush}
 139
 140 \func{virtual void}{Flush}{\void}
 141
 142 Shows all the messages currently in buffer and clears it. If the buffer
 143 is already empty, nothing happens.
 144
 145 \membersection{wxLog::HasPendingMessages}\label{haspendingmessages}
 146
 147 \constfunc{bool}{HasPendingMessages}{\void}
 148
 149 Returns true if there are any messages in the buffer (not yet shown to the
 150 user). (Almost) for internal use only.
 151
 152 \membersection{wxLog::SetVerbose}\label{wxlogsetverbose}
 153
 154 \func{void}{SetVerbose}{\param{bool }{ verbose = TRUE}}
 155
 156 Activates or desactivates verbose mode in which the verbose messages are
 157 logged as the normal ones instead of being silently dropped.
 158
 159 \membersection{wxLog::GetVerbose}\label{wxloggetverbose}
 160
 161 \constfunc{bool}{GetVerbose}{\void}
 162
 163 Returns whether the verbose mode is currently active.
 164
 165 \membersection{wxLog::SetTimestamp}\label{wxlogsettimestamp}
 166
 167 \func{void}{SetTimestamp}{\param{const char * }{ format}}
 168
 169 Sets the timestamp format prepended by the default log targets to all
 170 messages. The string may contain any normal characters as well as \%
 171 prefixed format specificators, see {\it strftime()} manual for details.
 172 Passing a null value (not empty string) to this function disables message timestamping.
 173
 174 \membersection{wxLog::GetTimestamp}\label{wxloggettimestamp}
 175
 176 \constfunc{const char *}{GetTimestamp}{\void}
 177
 178 Returns the current timestamp format string.
 179
 180 \membersection{wxLog::SetTraceMask}\label{wxlogsettracemask}
 181
 182 \func{static void}{SetTraceMask}{\param{wxTraceMask }{ mask}}
 183
 184 Sets the trace mask, see \helpref{Customization}{wxlogcustomization}
 185 section for details.
 186
 187 \membersection{wxLog::GetTraceMask}\label{wxloggettracemask}
 188
 189 Returns the current trace mask, see \helpref{Customization}{wxlogcustomization} section
 190 for details.
 191