## wxLog

wxLog class defines the interface for the log targets used by wxWindows logging functions as explained in the wxLog overview. The only situations when you need to directly use this class is when you want to derive your own log target because the existing ones don't satisfy your needs. Another case is if you wish to customize the behaviour of the standard logging classes (all of which respect the wxLog settings): for example, set which trace messages are logged and which are not or change (or even remove completely) the timestamp on the messages.

Otherwise, it is completely hidden behind the wxLogXXX() functions and you may not even know about its existence.

See log overview for the descriptions of wxWindows logging facilities.

Derived from

No base class

Include files

<wx/log.h>

Function groups

Static functions
Message buffering
Customization
wxLog::AddTraceMask
wxLog::OnLog
wxLog::GetActiveTarget
wxLog::SetActiveTarget
wxLog::DontCreateOnDemand
wxLog::Flush
wxLog::FlushActive
wxLog::HasPendingMessages
wxLog::SetVerbose
wxLog::GetVerbose
wxLog::SetTimestamp
wxLog::GetTimestamp
wxLog::SetTraceMask
wxLog::GetTraceMask
wxLog::IsAllowedTraceMask
wxLog::RemoveTraceMask

### Static functions

The functions in this section work with and manipulate the active log target. The OnLog() is called by the wxLogXXX() functions and invokes the DoLog() of the active log target if any. Get/Set methods are used to install/query the current active target and, finally, DontCreateOnDemand() disables the automatic creation of a standard log target if none actually exists. It is only useful when the application is terminating and shouldn't be used in other situations because it may easily lead to a loss of messages.

OnLog
GetActiveTarget
SetActiveTarget
DontCreateOnDemand

### Message buffering

Some of wxLog implementations, most notably the standard wxLogGui class, buffer the messages (for example, to avoid showing the user a zillion of modal message boxes one after another - which would be really annoying). Flush() shows them all and clears the buffer contents. Although this function doesn't do anything if the buffer is already empty, HasPendingMessages() is also provided which allows to explicitly verify it.

Flush
FlushActive
HasPendingMessages

### Customization

The functions below allow some limited customization of wxLog behaviour without writing a new log target class (which, aside of being a matter of several minutes, allows you to do anything you want).

The verbose messages are the trace messages which are not disabled in the release mode and are generated by wxLogVerbose. They are not normally shown to the user because they present little interest, but may be activated, for example, in order to help the user find some program problem.

As for the (real) trace messages, their handling depends on the settings of the (application global) trace mask. There are two ways to specify it: either by using SetTraceMask and GetTraceMask and using wxLogTrace which takes an integer mask or by using AddTraceMask for string trace masks.

The difference between bit-wise and string trace masks is that a message using integer trace mask will only be logged if all bits of the mask are set in the current mask while a message using string mask will be logged simply if the mask had been added before to the list of allowed ones.

For example,

    // wxTraceOleCalls is one of standard bit masks
    wxLogTrace(wxTraceRefCount | wxTraceOleCalls, "Active object ref count: %d", nRef);

will do something only if the current trace mask contains both `wxTraceRefCount` and `wxTraceOle`, but

    // wxTRACE_OleCalls is one of standard string masks
    wxLogTrace(wxTRACE_OleCalls, "IFoo::Bar() called");

will log the message if it was preceded by

    wxLog::AddTraceMask(wxTRACE_OleCalls);

Using string masks is simpler and allows to easily add custom ones, so this is the preferred way of working with trace messages. The integer trace mask is kept for compatibility and for additional (but very rarely needed) flexibility only.

The standard trace masks are given in wxLogTrace documentation.

Finally, the wxLog::DoLog() function automatically prepends a time stamp to all the messages. The format of the time stamp may be changed: it can be any string with % specificators fully described in the documentation of the standard strftime() function. For example, the default format is "[%d/%b/%y %H:%M:%S] " which gives something like "[17/Sep/98 22:10:16] " (without quotes) for the current date. Setting an empty string as the time format disables timestamping of the messages completely.

NB: Timestamping is disabled for Visual C++ users in debug builds by default because otherwise it would be impossible to directly go to the line from which the log message was generated by simply clicking in the debugger window on the corresponding error message. If you wish to enable it, please use SetTimestamp explicitly.

AddTraceMask
RemoveTraceMask
IsAllowedTraceMask
SetVerbose
GetVerbose
SetTimestamp
GetTimestamp
SetTraceMask
GetTraceMask

### wxLog::AddTraceMask

static void AddTraceMask(const wxString& mask)

Add the mask to the list of allowed masks for wxLogTrace.

See also: RemoveTraceMask

### wxLog::OnLog

static void OnLog(wxLogLevel level, const char * message)

Forwards the message at specified level to the DoLog() function of the active log target if there is any, does nothing otherwise.

### wxLog::GetActiveTarget

static wxLog * GetActiveTarget()

Returns the pointer to the active log target (may be NULL).

### wxLog::SetActiveTarget

static wxLog * SetActiveTarget(wxLog * logtarget)

Sets the specified log target as the active one. Returns the pointer to the previous active log target (may be NULL).

### wxLog::DontCreateOnDemand

static void DontCreateOnDemand()

Instructs wxLog to not create new log targets on the fly if there is none currently. (Almost) for internal use only.

### wxLog::Flush

virtual void Flush()

Shows all the messages currently in buffer and clears it. If the buffer is already empty, nothing happens.

### wxLog::FlushActive

static void FlushActive()

Flushes the current log target if any, does nothing if there is none.

See also:

Flush

### wxLog::HasPendingMessages

bool HasPendingMessages() const

Returns true if there are any messages in the buffer (not yet shown to the user). (Almost) for internal use only.

### wxLog::SetVerbose

void SetVerbose(bool verbose = TRUE)

Activates or desactivates verbose mode in which the verbose messages are logged as the normal ones instead of being silently dropped.

### wxLog::GetVerbose

bool GetVerbose() const

Returns whether the verbose mode is currently active.

### wxLog::SetTimestamp

void SetTimestamp(const char * format)

Sets the timestamp format prepended by the default log targets to all messages. The string may contain any normal characters as well as % prefixed format specificators, see strftime() manual for details. Passing a NULL value (not empty string) to this function disables message timestamping.

### wxLog::GetTimestamp

const char * GetTimestamp() const

Returns the current timestamp format string.

### wxLog::SetTraceMask

static void SetTraceMask(wxTraceMask mask)

Sets the trace mask, see Customization section for details.

### wxLog::GetTraceMask

Returns the current trace mask, see Customization section for details.

### wxLog::IsAllowedTraceMask

static bool IsAllowedTraceMask(const wxChar *mask)

Returns TRUE if the mask is one of allowed masks for wxLogTrace.

See also: AddTraceMask, RemoveTraceMask

### wxLog::RemoveTraceMask

static void RemoveTraceMask(const wxString& mask)

Remove the mask from the list of allowed masks for wxLogTrace.

See also: AddTraceMask