change device on-device-log to signal

third-party/realdds/include/realdds/dds-device.h

@@ -72,7 +72,7 @@ class dds_device
     typedef std::function< void(
         dds_time const & timestamp, char type, std::string const & text, nlohmann::json const & data ) >
         on_device_log_callback;
-    void on_device_log( on_device_log_callback cb );
+    rsutils::subscription on_device_log( on_device_log_callback && cb );
 
     typedef std::function< void( std::string const & id, nlohmann::json const & ) > on_notification_callback;
     rsutils::subscription on_notification( on_notification_callback && );

third-party/realdds/py/pyrealdds.cpp

@@ -908,11 +908,13 @@ PYBIND11_MODULE(NAME, m) {
                       [&self, callback]( std::shared_ptr< const nlohmann::json > const & pj )
                       { FN_FWD_CALL( dds_device, "on_metadata_available", callback( self, json_to_py( *pj ) ); ) } ) );
               } )
-        .def( FN_FWD( dds_device,
-                      on_device_log,
-                      (dds_device &, dds_time const &, char, std::string const &, py::object && ),
-                      (dds_time const & timestamp, char type, std::string const & text, nlohmann::json const & data),
-                      callback( self, timestamp, type, text, json_to_py( data ) ); ) )
+        .def( "on_device_log",
+              []( dds_device & self, std::function< void( dds_device &, dds_time const &, char, std::string const &, py::object && ) > callback )
+              {
+                  return std::make_shared< subscription >( self.on_device_log(
+                      [&self, callback]( dds_time const & timestamp, char type, std::string const & text, nlohmann::json const & data )
+                      { FN_FWD_CALL( dds_device, "on_device_log", callback( self, timestamp, type, text, json_to_py( data ) ); ) } ) );
+              } )
         .def( "on_notification",
               []( dds_device & self, std::function< void( dds_device &, std::string const &, py::object && ) > callback )
               {

third-party/realdds/src/dds-device-impl.cpp

@@ -348,25 +348,17 @@ void dds_device::impl::on_log( nlohmann::json const & j, eprosima::fastdds::dds:
         {
             if( ! entry.is_array() )
                 throw std::runtime_error( "not an array" );
-            if( entry.size() > 4 )
-                throw std::runtime_error( "too long" );
+            if( entry.size() < 3 || entry.size() > 4 )
+                throw std::runtime_error( "bad array length" );
             auto timestamp = time_from( rsutils::json::get< dds_nsec >( entry, 0 ) );
-            auto const stype = rsutils::json::get< std::string >( entry, 1 );
+            auto const & stype = rsutils::json::string_ref( entry[1] );
             if( stype.length() != 1 || ! strchr( "EWID", stype[0] ) )
                 throw std::runtime_error( "type not one of 'EWID'" );
             char const type = stype[0];
-            auto const text = rsutils::json::get< std::string >( entry, 2 );
-            nlohmann::json data;
-            if( entry.size() > 3 )
-            {
-                data = entry.at( 3 );
-                if( ! data.is_object() )
-                    throw std::runtime_error( "data is not an object" );
-            }
+            auto const & text = rsutils::json::string_ref( entry[2] );
+            nlohmann::json const & data = entry.size() > 3 ? entry[3] : rsutils::json::null_json;
 
-            if( _on_device_log )
-                _on_device_log( timestamp, type, text, data );
-            else
+            if( ! _on_device_log.raise( timestamp, type, text, data ) )
                 LOG_DEBUG( "[" << debug_name() << "][" << timestr( timestamp ) << "][" << type << "] " << text
                                << " [" << data << "]" );
         }

third-party/realdds/src/dds-device-impl.h

@@ -94,10 +94,15 @@ class dds_device::impl
         return _on_metadata_available.subscribe( std::move( cb ) );
     }
 
-    typedef std::function< void(
-        dds_time const & timestamp, char type, std::string const & text, nlohmann::json const & data ) >
-        on_device_log_callback;
-    void on_device_log( on_device_log_callback cb ) { _on_device_log = cb; }
+    using on_device_log_signal = rsutils::signal< dds_time const &,          // timestamp
+                                                  char,                      // type
+                                                  std::string const &,       // text
+                                                  nlohmann::json const & >;  // data
+    using on_device_log_callback = on_device_log_signal::callback;
+    rsutils::subscription on_device_log( on_device_log_callback && cb )
+    {
+        _on_device_log.subscribe( std::move( cb ) );
+    }
 
     using on_notification_signal = rsutils::signal< std::string const &, nlohmann::json const & >;
     using on_notification_callback = on_notification_signal::callback;
@@ -128,7 +133,7 @@ class dds_device::impl
     void handle_notification( nlohmann::json const &, eprosima::fastdds::dds::SampleInfo const & );
 
     on_metadata_available_signal _on_metadata_available;
-    on_device_log_callback _on_device_log;
+    on_device_log_signal _on_device_log;
     on_notification_signal _on_notification;
 };
 

third-party/realdds/src/dds-device.cpp

@@ -122,9 +122,9 @@ rsutils::subscription dds_device::on_metadata_available( on_metadata_available_c
     return _impl->on_metadata_available( std::move( cb ) );
 }
 
-void dds_device::on_device_log( on_device_log_callback cb )
+rsutils::subscription dds_device::on_device_log( on_device_log_callback && cb )
 {
-    _impl->on_device_log( cb );
+    return _impl->on_device_log( std::move( cb ) );
 }
 
 rsutils::subscription dds_device::on_notification( on_notification_callback && cb )