wxTextCtrl as a spdlog sink.

LogWindow.h

#ifndef LOG_WINDOW_H
#define LOG_WINDOW_H

// Say you have a MyFrame class derived from wxFrame and you want to add a wxWindow to that and use it as a spdlog sink.
// Declaration of your MyFrame class should be like this:
//     #include "LogWindow.h"
//     class MyFrame: public wxFrame {
//         public:
//             MyFrame();
//         private:
//             std::shared_ptr<spdlog::sinks::LogWindow> logWindowPtr;
//             std::shared_ptr<spdlog::logger> spdlogger;
//     };
// Constructor of your MyFrame should be something like this:
//     MyFrame::MyFrame(): wxFrame( NULL, wxID_ANY, "Hello World" ), logWindowPtr( spdlog::sinks::LogWindowPtr( new spdlog::sinks::LogWindow( this ), spdlog::sinks::LogWindowDeleter() ) ), spdlogger( std::make_shared<spdlog::logger>( "wxWidgetsLogger", logWindowPtr ) ) {
//         spdlog::register_logger( spdlogger );
//         ...
//     }
// Then you will be able to use e.g.
//     spdlog::get( "wxWidgetsLogger" )->info( "Logger started!" );
// from other parts of your code as soon as MyFrame is constructed.

#include <spdlog/spdlog.h>
#include <spdlog/details/log_msg.h>
#include <spdlog/formatter.h>
#include <spdlog/pattern_formatter.h>
#include <spdlog/sinks/sink.h>
#include <wx/wx.h>
#include <wx/textctrl.h>

#include <memory>

namespace spdlog {
	namespace sinks {
		class LogWindow: public wxTextCtrl, public sink {
			public:
				LogWindow( wxWindow * parent ): wxTextCtrl( parent, wxID_ANY, wxEmptyString, wxDefaultPosition, wxSize( 1024, 768 ), wxTE_MULTILINE | wxTE_READONLY | wxTE_LEFT | wxTE_BESTWRAP | wxBORDER_NONE | wxALWAYS_SHOW_SB ), formatter_( details::make_unique<spdlog::pattern_formatter>() ) {};
				~LogWindow() = default;
				void log( const details::log_msg & msg ) {
					memory_buf_t formatted;
					formatter_->format( msg, formatted );
					AppendText( std::string( formatted.data(), formatted.size() ) );
					ScrollLines( 1 );
				};
				void flush() { Clear(); };
				void set_pattern( const std::string & pattern ) {};
				void set_formatter( std::unique_ptr<spdlog::formatter> sink_formatter ) { formatter_ = std::move( sink_formatter ); };
				void set_level( level::level_enum log_level ) { level_.store( log_level, std::memory_order_relaxed ); };
				level::level_enum level() const { return static_cast<spdlog::level::level_enum>(level_.load( std::memory_order_relaxed )); };
				bool  should_log( level::level_enum msg_level ) const { return msg_level >= level_.load( std::memory_order_relaxed ); };
			protected:
				level_t level_{ level::trace };
				std::unique_ptr<spdlog::formatter> formatter_;
		};

		using LogWindowPtr = std::shared_ptr<LogWindow>;

		// We need a dummy deleter object to let wxWidgets handle its own memory management
		struct LogWindowDeleter {
			void operator()( spdlog::sinks::LogWindow * p ) const {};
		};
	}
}

#endif