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logger.md

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Synopsis:

#include "log/log.h"

log::log(MSG(info) << "test" << 1337);

auto msg = MSG(warn);
msg.fmt("%d %8.3f", 10, 2.0) << "lol test";
msg << "rofl";
log::log(msg);

villager.log(MSG(dbg) <<
        "This is how you're supposed to break log lines that are too"
        "long. " << 1337 <<
        "foo");

throw Error(MSG(err) << "Exceptions use the MSG system as well!");

The logging system consists of the following main components:

  • log::LogSource: Objects that have a .log() member function and accept messages.
  • log::log(): Accepts messages using a "general" LogSource.
  • MSG: Macro that creates objects for the log() methods.
  • log::LogSink: prints/renders/writes log messages.

MSG

The MSG macro collects all sorts of information, including __FILE__ and __LINE__. MSG evaluates to a log::MessageBuilder constructor; the message builder accepts input in two ways:

  • "c++-style" with operator << ("iostreams")
  • "c-style" with .fmt() ("printf")

All input is appended to the internal log::message object. The MessageBuilder is auto-converted to log::message if needed.

message

Dumb struct that holds the text and metadata.

LogSource

Any class that wishes to provide .log() may inherit from log::LogSource. It just needs to implement virtual std::string logsource_name().

LogSink

A list of all log sinks is maintained (by the LogSink constructor/destructor) in LogSink::log_sink_list.

Each time a message is passed to LogSource::log(), it is forwarded to each LogSink, which may proceed as it wishes.

Popular LogSink classes include¹:

Sink What does it do to my messages?
StdOutSink Prints them to stdout.
FileSink Writes them and all their metadata to a file.
InGameSink Displays them next to the in-game objects they refer to.
ConsoleSink Prints them to a in-game terminal buffer.

¹) Disclaimer: May not actually be popular and/or available.