From 1a4788e2484bed7e06a4172e27704d8be52858ce Mon Sep 17 00:00:00 2001
From: "k.koide" <k.koide@aist.go.jp>
Date: Tue, 4 Aug 2026 17:26:39 +0900
Subject: [PATCH] add self callback_sink

---
 .../src/glim/logger_hook_demo.cpp             | 24 +++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/modules/example/logger_hook_demo/src/glim/logger_hook_demo.cpp b/modules/example/logger_hook_demo/src/glim/logger_hook_demo.cpp
index 3335693..5a9e61e 100644
--- a/modules/example/logger_hook_demo/src/glim/logger_hook_demo.cpp
+++ b/modules/example/logger_hook_demo/src/glim/logger_hook_demo.cpp
@@ -1,18 +1,35 @@
 #include <iostream>
 #include <spdlog/spdlog.h>
-#include <spdlog/sinks/callback_sink.h>
 #include <glim/util/logging.hpp>
 #include <glim/util/extension_module.hpp>
 
 namespace glim {
 
+/// @brief Callback sink that calls a user-defined callback function for each log message.
+/// @note  This is identical to spdlog::sinks::callback_sink, just for backwards compatibility with older spdlog versions.
+template <typename Mutex>
+class callback_sink final : public spdlog::sinks::base_sink<Mutex> {
+public:
+  using Callback = std::function<void(const spdlog::details::log_msg& msg)>;
+  explicit callback_sink(const Callback& callback) : callback_{callback} {}
+
+protected:
+  void sink_it_(const spdlog::details::log_msg& msg) override { callback_(msg); }
+  void flush_() override {}
+
+private:
+  Callback callback_;
+};
+
+using callback_sink_mt = callback_sink<std::mutex>;
+
 /// @brief A demo extension module that hooks into all loggers and prints log messages to the console.
 /// @note  This module is assumed to be loaded after all other modules, so that it can hook into all loggers.
 class LoggerHookDemo : public ExtensionModule {
 public:
   LoggerHookDemo() : logger(create_module_logger("loghook")) {
     // Message callback sink to be added to all loggers
-    auto sink = std::make_shared<spdlog::sinks::callback_sink_mt>([this](const auto& msg) { msg_callback(msg); });
+    auto sink = std::make_shared<callback_sink_mt>([this](const auto& msg) { msg_callback(msg); });
 
     // Add the callback sink to all existing loggers
     spdlog::apply_all([this, sink](std::shared_ptr<spdlog::logger> logger) {
@@ -37,8 +54,7 @@ class LoggerHookDemo : public ExtensionModule {
   }
 
 private:
-  // Logger
-  std::shared_ptr<spdlog::logger> logger;
+  std::shared_ptr<spdlog::logger> logger;  // Logger
 };
 }  // namespace glim