-\section{Log classes overview}\label{wxlogoverview}
+\section{wxLog classes overview}\label{wxlogoverview}
-Classes: \helpref{wxLog}{wxlog}, \helpref{wxLogStderr}{wxlogstderr},
-\helpref{wxLogOstream}{wxlogostream}, \helpref{wxLogTextCtrl}{wxlogtextctrl},
-\helpref{wxLogWindow}{wxlogwindow}, \helpref{wxLogGui}{wxloggui},
-\helpref{wxLogNull}{wxlognull}
+Classes: \helpref{wxLog}{wxlog}, wxLogStderr,
+wxLogOstream, wxLogTextCtrl, wxLogWindow, wxLogGui, wxLogNull
This is a general overview of logging classes provided by wxWindows. The word
logging here has a broad sense, including all of the program output, not only
\item{\bf wxLogVerbose} is for verbose output. Normally, it's suppressed, but
might be activated if the user wishes to know more details about the program
progress (another, but possibly confusing name for the same function is {\bf
-wxLogInfo}
+wxLogInfo}).
\item{\bf wxLogStatus} is for status messages - they will go into the status
-bar of the active or specified (as the first argument)
-\helpref{wxFrame}{wxframe} if it has one.
+bar of the active or specified (as the first argument) \helpref{wxFrame}{wxframe} if it has one.
\item{\bf wxLogSysError} is mostly used by wxWindows itself, but might be
handy for logging errors after system call (API function) failure. It logs the
-specified message text as well as the last system error code ({\it errno} or
-{\it ::GetLastError()} depending on the platform) and the corresponding error
+specified message text as well as the last system error
+code ({\it errno} or {\it ::GetLastError()} depending on the platform) and the corresponding error
message. The second form of this function takes the error code explitly as the
first argument.
\item{\bf wxLogDebug} is {\bf the} right function for debug output. It only
does anything at all in the debug mode (when the preprocessor symbol
\_\_WXDEBUG\_\_ is defined) and expands to nothing in release mode (otherwise).
+{\bf Tip:} under Windows, you must either run the program under debugger or
+use a 3rd party program such as \urlref{DbgView}{http://www.sysinternals.com}
+to actually see the debug output.
\item{\bf wxLogTrace} as {\bf wxLogDebug} only does something in debug
build. The reason for making it a separate function from it is that usually
there are a lot of trace messages, so it might make sense to separate them
to further restrict the amount of messages generated.
\end{itemize}
-% VZ: Julian, am I pushing too much here?
The usage of these functions should be fairly straightforward, however it may
be asked why not use the other logging facilities, such as C standard stdio
functions or C++ streams. The short answer is that they're all very good
classes are. Some of advantages in using wxWindows log functions are:
\begin{itemize}\itemsep=0pt
-\item{Portability} It's a common practice to use {\it printf()} statements or
+\item{\bf Portability} It's a common practice to use {\it printf()} statements or
cout/cerr C++ streams for writing out some (debug or otherwise) information.
-Although it works just fine under Unix, these messages go strictly nowever
+Although it works just fine under Unix, these messages go strictly nowhere
under Windows where the stdout of GUI programs is not assigned to anything.
Thus, you might view {\it wxLogMessage()} as a simple substitute for {\it
printf()}.
-\item{Flexibility} The output of wxLog functions can be redirected or
+\item{\bf Flexibility} The output of wxLog functions can be redirected or
suppressed entirely based on their importance, which is either impossible or
difficult to do with traditional methods. For example, only error messages, or
only error messages and warnings might be logged, filtering out all
informational messages.
-\item{Completeness} Usually, an error message should be presented to the user
+\item{\bf Completeness} Usually, an error message should be presented to the user
when some operation fails. Let's take a quite simple but common case of a file
error: suppose that you're writing your data file on disk and there is not
enough space. The actual error might have been detected inside wxWindows code
wxWindows has the notion of a {\it log target}: it's just a class deriving
from \helpref{wxLog}{wxlog}. As such, it implements the virtual functions of
the base class which are called when a message is logged. Only one log target
-is {\it active} at any moment, this is the one used by \it{wxLogXXX()}
+is {\it active} at any moment, this is the one used by {\it wxLogXXX()}
functions. The normal usage of a log object (i.e. object of a class derived
from wxLog) is to install it as the active target with a call to {\it
SetActiveTarget()} and it will be used automatically by all subsequent calls
\item{\bf wxLogNull} The last log class is quite particular: it doesn't do
anything. The objects of this class may be instantiated to (temporarily)
suppress output of {\it wxLogXXX()} functions. As an example, trying to open a
-non-existing file will usually provoke an error message, but if you for some
-reason it's unwanted, just use this construction:
+non-existing file will usually provoke an error message, but if for some
+reasons it's unwanted, just use this construction:
{\small
\begin{verbatim}
projects / wxWidgets.git / blobdiff