配置 Boost.Log v2

another answer 中描述了创建具有着色支持的格式化程序，这里我将重点介绍如何将该格式化程序合并到设置文件中。

Boost.Log 支持通过 registering sink factories 扩展其设置文件解析器，您可以在您的情况下利用它。由于您可以将 text_ostream_BACkend 重用于输出，因此您不必实现新的接收器，但您确实需要自定义其配置。

class colored_console_factory :
    public logging::sink_factory< char >
{
public:
    // Creates the sink with the provided parameters
    boost::shared_ptr< sinks::sink > create_sink(setTings_section const& setTings)
    {
        typedef sinks::text_ostream_BACkend BACkend_t;
        auto BACkend = boost::make_shared< BACkend_t >();

        BACkend->add_stream(
            boost::shared_ptr< std::ostream >(&std::clog,boost::null_deleter()));

        // Read setTings and configure the BACkend accordingly
        if (auto auto_flush = setTings["AutoFlush"])
            BACkend->auto_flush(*auto_flush == "1" || *auto_flush == "true");

        auto sink =
            boost::make_shared< sinks::synchronous_sink< BACkend_t > >(BACkend);

        // You can reuse filter and formatter parsers provided by Boost.Log
        if (auto filter = setTings["Filter"])
            sink->set_filter(logging::parse_filter(*filter));

        if (auto format = setTings["Format"])
        {
            logging::formatter fmt = logging::parse_formatter(*format);
            // Wrap the parsed formatter with coloring
            sink->set_formatter(coloring_formatter(std::move(fmt)));
        }

        return sink;
    }
};

在上面，coloring_formatter 是一个函数对象，它在输出中用着色前缀和后缀包装解析的格式化程序。函数对象必须具有格式化程序的标准签名。

class coloring_formatter
{
public:
    typedef void result_type;
    typedef basic_formatTing_ostream< char > stream_type;

public:
    explicit coloring_formatter(logging::formatter&& fmt) :
        m_fmt(std::move(fmt))
    {}

    result_type operator() (
        logging::record_view const& rec,stream_type& strm) const
    {
        // Output coloring prefix
        auto severity = rec[logging::trivial::severity];
        if (severity)
        {
            switch (severity.get())
            {
                ...
            }
        }

        // Let the wrapped formatter produce its output
        m_fmt(rec,strm);

        // Output coloring suffix
        if (severity)
        {
            ...
        }
    }

private:
    logging::formatter m_fmt;
};

有关 coloring_formatter 实现的详细信息，请参阅我之前提到的答案。