# LV2 Log

http://lv2plug.in/ns/ext/log
A feature for writing log messages.

Version | 2.4
Date | 2018-03-16
Discuss | devel@lists.lv2plug.in (subscribe)
Developer | David Robillard

- Index
- Reference
- History
- API

This extension defines a feature, log:log, which allows plugins to print log messages with an API much like the standard C printf functions. This allows, for example, plugin logs to be nicely presented to the user in a graphical user interface.

Different log levels (e.g. error or information) are defined by URI and passed as an LV2_URID. This document defines the typical levels which should be sufficient, but implementations may define and use additional levels to suit their needs.

## Index

Classes | Instances | Files
--- | --- | ---
Entry Error Note Trace Warning | log | log.h log.ttl lv2-log.doap.ttl

## Reference

### Class log:Entry

Log Entry

A log entry. Subclasses of this class can be passed to LV2_Log_Log methods to describe the nature of the log message.

### Class log:Error

Error

An error message.

Sub-class of | log:Entry

### Class log:Note

Note

An informative message.

Sub-class of | log:Entry

### Class log:Trace

Trace

A debugging trace. These entries should not be displayed during normal operation, but the host may implement an option to display them for debugging purposes.

This entry type is special in that it may be written to in a real-time thread. It is assumed that if debug tracing is enabled, real-time considerations are not a concern.

Sub-class of | log:Entry

### Class log:Warning

Warning

A warning message.

Sub-class of | log:Entry

### Instance log:log

A feature which plugins may use to log messages. To support this feature, the host must pass an LV2_Feature to LV2_Descriptor::instantiate() with URI LV2_LOG__log and data pointed to an instance of LV2_Log_Log.

Type | lv2:Feature

## History

Version 2.4 (2016-07-30)
  - Add lv2_log_logger_set_map() for changing the URI map of an existing logger.
Version 2.2 (2014-01-04)
  - Add missing include string.h to logger.h for memset.
Version 2.0 (2013-01-08)
  - Add logger convenience API.
Version 1.0 (2012-04-17)
  - Initial release.