Refactoring logging architecture to enable user logging module loading.

23 files changed, 216 insertions, 78 deletions

diff --git a/src/argaze/ArFeatures.py b/src/argaze/ArFeatures.py
index 1b3e504..8c9b3c8 100644
--- a/src/argaze/ArFeatures.py
+++ b/src/argaze/ArFeatures.py
@@ -8,9 +8,11 @@ __copyright__ = "Copyright 2023, Ecole Nationale de l'Aviation Civile (ENAC)"
 __license__ = "BSD"
 
 from typing import TypeVar, Tuple, Any, Iterator, Union
+from types import ModuleType
 from dataclasses import dataclass, field
 import json
 import os
+import sys
 import importlib
 from inspect import getmembers
 import threading
@@ -108,6 +110,7 @@ class ArLayer(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 		aoi_scan_path: AOI scan path object
 		aoi_scan_path_analyzers: dictionary of AOI scan path analyzers
 		draw_parameters: default parameters passed to draw method
+		logging_module: path to logging module file in working directory
 	"""
 
 	name: str
@@ -116,6 +119,7 @@ class ArLayer(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 	aoi_scan_path: GazeFeatures.AOIScanPath = field(default_factory=GazeFeatures.AOIScanPath)
 	aoi_scan_path_analyzers: dict = field(default_factory=dict)
 	draw_parameters: dict = field(default_factory=DEFAULT_ARLAYER_DRAW_PARAMETERS)
+	logging_module: ModuleType = field(default=None)
 
 	def __post_init__(self):
 
@@ -152,6 +156,11 @@ class ArLayer(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 			working_directory: folder path where to load files when a dictionary value is a relative filepath.
 		"""
 
+		# Append working directory to the Python path
+		if working_directory is not None:
+
+			sys.path.append(working_directory)
+
 		# Load name
 		try:
 
@@ -297,6 +306,26 @@ class ArLayer(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 
 			new_layer_draw_parameters = DEFAULT_ARLAYER_DRAW_PARAMETERS
 
+		# Load logging module
+		try:
+
+			new_logging_module_value = layer_data.pop('logging_module')
+
+			# str: relative path to file
+			if type(new_logging_module_value) == str:
+
+				logging_module_name = new_logging_module_value.split('.')[0]
+				
+				# Import logging module
+				self.logging_module = importlib.import_module(logging_module_name)
+
+				# Register loggers as pipeline step observers
+				self.observers = self.logging_module.__loggers__
+
+		except KeyError:
+
+			pass
+
 		# Create layer
 		return ArLayer(new_layer_name, \
 						new_aoi_scene, \
@@ -388,7 +417,7 @@ class ArLayer(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 
 				# Update looked aoi thanks to aoi matcher
 				# Note: don't filter valid/unvalid and finished/unfinished fixation/saccade as we don't know how the aoi matcher works internally
-				self.__looked_aoi_name, _ = self.aoi_matcher.match(self.aoi_scene, gaze_movement)
+				self.__looked_aoi_name, _ = self.aoi_matcher.match(timestamp, self.aoi_scene, gaze_movement)
 
 			# Valid and finished gaze movement has been identified
 			if gaze_movement.valid and gaze_movement.finished:
@@ -406,7 +435,7 @@ class ArLayer(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 							# Analyze aoi scan path
 							for aoi_scan_path_analyzer_module_path, aoi_scan_path_analyzer in self.aoi_scan_path_analyzers.items():
 
-								aoi_scan_path_analyzer.analyze(self.aoi_scan_path)
+								aoi_scan_path_analyzer.analyze(timestamp, self.aoi_scan_path)
 
 							# Update aoi scan path analyzed state
 							self.__aoi_scan_path_analyzed = True
@@ -486,6 +515,7 @@ class ArFrame(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 		background: picture to draw behind
 		layers: dictionary of AOI layers
 		image_parameters: default parameters passed to image method
+		logging_module: path to logging module file in working directory
 	"""
 
 	name: str
@@ -499,6 +529,7 @@ class ArFrame(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 	background: numpy.array = field(default_factory=lambda : numpy.array([]))
 	layers: dict = field(default_factory=dict)
 	image_parameters: dict = field(default_factory=DEFAULT_ARFRAME_IMAGE_PARAMETERS)
+	logging_module: ModuleType = field(default=None)
 
 	def __post_init__(self):
 
@@ -531,6 +562,11 @@ class ArFrame(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 			working_directory: folder path where to load files when a dictionary value is a relative filepath.
 		"""
 
+		# Append working directory to the Python path
+		if working_directory is not None:
+
+			sys.path.append(working_directory)
+
 		# Load name
 		try:
 
@@ -718,6 +754,26 @@ class ArFrame(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 
 			new_frame_image_parameters = DEFAULT_ARFRAME_IMAGE_PARAMETERS
 
+		# Load logging module
+		try:
+
+			new_logging_module_value = frame_data.pop('logging_module')
+
+			# str: relative path to file
+			if type(new_logging_module_value) == str:
+
+				logging_module_name = new_logging_module_value.split('.')[0]
+				
+				# Import logging module
+				self.logging_module = importlib.import_module(logging_module_name)
+
+				# Register loggers as pipeline step observers
+				self.observers = self.logging_module.__loggers__
+
+		except KeyError:
+
+			pass
+
 		# Create frame
 		return ArFrame(new_frame_name, \
 						new_frame_size, \
@@ -852,7 +908,7 @@ class ArFrame(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 							# Analyze aoi scan path
 							for scan_path_analyzer_module_path, scan_path_analyzer in self.scan_path_analyzers.items():
 
-								scan_path_analyzer.analyze(self.scan_path)
+								scan_path_analyzer.analyze(timestamp, self.scan_path)
 
 							# Update scan path analyzed state
 							self.__scan_path_analyzed = True
@@ -869,7 +925,7 @@ class ArFrame(DataFeatures.SharedObject, DataFeatures.PipelineStepObject):
 				scale = numpy.array([self.heatmap.size[0] / self.size[0], self.heatmap.size[1] / self.size[1]])
 
 				# Update heatmap image
-				self.heatmap.update(self.__calibrated_gaze_position.value * scale)
+				self.heatmap.update(timestamp, self.__calibrated_gaze_position.value * scale)
 
 			# Look layers with valid identified gaze movement
 			# Note: don't filter valid/unvalid finished/unfished gaze movement to allow layers to reset internally
diff --git a/src/argaze/ArUcoMarkers/ArUcoDetector.py b/src/argaze/ArUcoMarkers/ArUcoDetector.py
index 6d12f3d..c562467 100644
--- a/src/argaze/ArUcoMarkers/ArUcoDetector.py
+++ b/src/argaze/ArUcoMarkers/ArUcoDetector.py
@@ -257,7 +257,7 @@ class ArUcoDetector(DataFeatures.PipelineStepObject):
         return output
 
     @DataFeatures.PipelineStepMethod
-    def detect_markers(self, image: numpy.array) -> float:
+    def detect_markers(self, timestamp: int|float, image: numpy.array) -> float:
         """Detect all ArUco markers into an image.
 
         !!! danger "DON'T MIRROR IMAGE"
diff --git a/src/argaze/AreaOfInterest/AOIFeatures.py b/src/argaze/AreaOfInterest/AOIFeatures.py
index 6457e8f..002b251 100644
--- a/src/argaze/AreaOfInterest/AOIFeatures.py
+++ b/src/argaze/AreaOfInterest/AOIFeatures.py
@@ -600,7 +600,7 @@ class Heatmap(DataFeatures.PipelineStepObject):
         self.__point_spread_buffer_size = self.buffer
 
     @DataFeatures.PipelineStepMethod
-    def update(self, point: tuple):
+    def update(self, timestamp: int|float, point: tuple):
         """Update heatmap image."""
 
         point_spread = self.point_spread(point)
diff --git a/src/argaze/DataFeatures.py b/src/argaze/DataFeatures.py
index 4dfd911..ac4a176 100644
--- a/src/argaze/DataFeatures.py
+++ b/src/argaze/DataFeatures.py
@@ -418,15 +418,23 @@ class SharedObject():
         return timestamped
 
 class PipelineStepObject():
-    """Abstract class to assess pipeline step methods execution time."""
+    """Abstract class to assess pipeline step methods execution time.
+
+    Parameters:
+        execution_times: dictionary with each PipelineStepMethod execution time in ms.
+    """
 
     execution_times: dict = {}
-    """Execution time for each mehtod in ms."""
+    observers: dict = {}
 
 def PipelineStepMethod(method):
-    """Define a decorator use into PipelineStepObject class to declare pipeline method."""
+    """Define a decorator use into PipelineStepObject class to declare pipeline method.
+
+    !!! danger
+        PipelineStepMethod must have a timestamp as first argument.
+    """
 
-    def wrapper(self, *args, **kw):
+    def wrapper(self, timestamp, *args, **kw):
         """Wrap pipeline step method to measure execution time."""
 
         # Initialize execution time assessment
@@ -434,13 +442,38 @@ def PipelineStepMethod(method):
         
         try:
 
-            result = method(self, *args, **kw)
+            # Execute wrapped method
+            result = method(self, timestamp, *args, **kw)
 
         finally:
 
             # Measure execution time
             self.execution_times[method.__name__] = (time.perf_counter() - start) * 1e3
 
+        # Notify observers that method has been called
+        subscription_name = f'on_{method.__name__}'
+
+        for observer_name, observer in self.observers.items():
+
+            # Does the observer cares about this method?
+            try: 
+
+                subscription = getattr(observer, subscription_name)
+
+                # Call subscription
+                subscription(timestamp, self)
+
+            except AttributeError:
+
+                pass
+
         return result
 
     return wrapper
+
+class PipelineStepObserver():
+    """Define abstract class to observe pipeline step object use.
+
+    !!! note
+        To subscribe to a method call, the inherited class simply needs to define 'on_<method_name>' functions with timestamp and object argument.
+    """
diff --git a/src/argaze/GazeAnalysis/Basic.py b/src/argaze/GazeAnalysis/Basic.py
index b75932a..55c0737 100644
--- a/src/argaze/GazeAnalysis/Basic.py
+++ b/src/argaze/GazeAnalysis/Basic.py
@@ -27,7 +27,7 @@ class ScanPathAnalyzer(GazeFeatures.ScanPathAnalyzer):
         self.__step_fixation_durations_average = 0
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, scan_path: GazeFeatures.ScanPathType):
+    def analyze(self, timestamp: int|float, scan_path: GazeFeatures.ScanPathType):
 
         self.__path_duration = scan_path.duration
 
@@ -72,7 +72,7 @@ class AOIScanPathAnalyzer(GazeFeatures.AOIScanPathAnalyzer):
         self.__step_fixation_durations_average = 0
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, aoi_scan_path: GazeFeatures.ScanPathType):
+    def analyze(self, timestamp: int|float, aoi_scan_path: GazeFeatures.ScanPathType):
 
         self.__path_duration = aoi_scan_path.duration
 
diff --git a/src/argaze/GazeAnalysis/DeviationCircleCoverage.py b/src/argaze/GazeAnalysis/DeviationCircleCoverage.py
index f890701..e80b198 100644
--- a/src/argaze/GazeAnalysis/DeviationCircleCoverage.py
+++ b/src/argaze/GazeAnalysis/DeviationCircleCoverage.py
@@ -38,7 +38,7 @@ class AOIMatcher(GazeFeatures.AOIMatcher):
         self.__matched_region = None
 
     @DataFeatures.PipelineStepMethod
-    def match(self, aoi_scene, gaze_movement) -> Tuple[str, AOIFeatures.AreaOfInterest]:
+    def match(self, timestamp: int|float, aoi_scene, gaze_movement) -> Tuple[str, AOIFeatures.AreaOfInterest]:
         """Returns AOI with the maximal fixation's deviation circle coverage if above coverage threshold."""
 
         if GazeFeatures.is_fixation(gaze_movement):
diff --git a/src/argaze/GazeAnalysis/DispersionThresholdIdentification.py b/src/argaze/GazeAnalysis/DispersionThresholdIdentification.py
index 011c272..39895fd 100644
--- a/src/argaze/GazeAnalysis/DispersionThresholdIdentification.py
+++ b/src/argaze/GazeAnalysis/DispersionThresholdIdentification.py
@@ -143,7 +143,7 @@ class GazeMovementIdentifier(GazeFeatures.GazeMovementIdentifier):
         self.__saccade_positions = GazeFeatures.TimeStampedGazePositions()
 
     @DataFeatures.PipelineStepMethod
-    def identify(self, ts, gaze_position, terminate=False) -> GazeMovementType:
+    def identify(self, ts: int|float, gaze_position, terminate=False) -> GazeMovementType:
 
         # Ignore non valid gaze position
         if not gaze_position.valid:
diff --git a/src/argaze/GazeAnalysis/Entropy.py b/src/argaze/GazeAnalysis/Entropy.py
index a62dfe6..eeccfa7 100644
--- a/src/argaze/GazeAnalysis/Entropy.py
+++ b/src/argaze/GazeAnalysis/Entropy.py
@@ -38,7 +38,7 @@ class AOIScanPathAnalyzer(GazeFeatures.AOIScanPathAnalyzer):
         self.__transition_entropy = -1
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, aoi_scan_path: GazeFeatures.AOIScanPathType):
+    def analyze(self, timestamp: int|float, aoi_scan_path: GazeFeatures.AOIScanPathType):
 
         assert(len(aoi_scan_path) > 1)
 
diff --git a/src/argaze/GazeAnalysis/ExploreExploitRatio.py b/src/argaze/GazeAnalysis/ExploreExploitRatio.py
index 5516349..1f7fad0 100644
--- a/src/argaze/GazeAnalysis/ExploreExploitRatio.py
+++ b/src/argaze/GazeAnalysis/ExploreExploitRatio.py
@@ -34,7 +34,7 @@ class ScanPathAnalyzer(GazeFeatures.ScanPathAnalyzer):
         self.__explore_exploit_ratio = 0.
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, scan_path: GazeFeatures.ScanPathType):
+    def analyze(self, timestamp: int|float, scan_path: GazeFeatures.ScanPathType):
 
         assert(len(scan_path) > 1)
 
diff --git a/src/argaze/GazeAnalysis/FocusPointInside.py b/src/argaze/GazeAnalysis/FocusPointInside.py
index d559ac2..bf97d0d 100644
--- a/src/argaze/GazeAnalysis/FocusPointInside.py
+++ b/src/argaze/GazeAnalysis/FocusPointInside.py
@@ -31,7 +31,7 @@ class AOIMatcher(GazeFeatures.AOIMatcher):
         self.__matched_gaze_movement = None
 
     @DataFeatures.PipelineStepMethod
-    def match(self, aoi_scene, gaze_movement) -> Tuple[str, AOIFeatures.AreaOfInterest]:
+    def match(self, timestamp: int|float, aoi_scene, gaze_movement) -> Tuple[str, AOIFeatures.AreaOfInterest]:
         """Returns AOI containing fixation focus point."""
 
         if GazeFeatures.is_fixation(gaze_movement):
diff --git a/src/argaze/GazeAnalysis/KCoefficient.py b/src/argaze/GazeAnalysis/KCoefficient.py
index 41338a3..40e3ddd 100644
--- a/src/argaze/GazeAnalysis/KCoefficient.py
+++ b/src/argaze/GazeAnalysis/KCoefficient.py
@@ -31,7 +31,7 @@ class ScanPathAnalyzer(GazeFeatures.ScanPathAnalyzer):
         self.__K = 0
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, scan_path: GazeFeatures.ScanPathType):
+    def analyze(self, timestamp: int|float, scan_path: GazeFeatures.ScanPathType):
 
         assert(len(scan_path) > 1)
 
@@ -88,7 +88,7 @@ class AOIScanPathAnalyzer(GazeFeatures.AOIScanPathAnalyzer):
         self.__K = 0
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, aoi_scan_path: GazeFeatures.AOIScanPathType) -> float:
+    def analyze(self, timestamp: int|float, aoi_scan_path: GazeFeatures.AOIScanPathType) -> float:
 
         assert(len(aoi_scan_path) > 1)
 
diff --git a/src/argaze/GazeAnalysis/LempelZivComplexity.py b/src/argaze/GazeAnalysis/LempelZivComplexity.py
index f6a49ab..53d4285 100644
--- a/src/argaze/GazeAnalysis/LempelZivComplexity.py
+++ b/src/argaze/GazeAnalysis/LempelZivComplexity.py
@@ -32,7 +32,7 @@ class AOIScanPathAnalyzer(GazeFeatures.AOIScanPathAnalyzer):
         self.__lempel_ziv_complexity = 0
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, aoi_scan_path: GazeFeatures.AOIScanPathType):
+    def analyze(self, timestamp: int|float, aoi_scan_path: GazeFeatures.AOIScanPathType):
 
         assert(len(aoi_scan_path) > 1)
 
diff --git a/src/argaze/GazeAnalysis/NGram.py b/src/argaze/GazeAnalysis/NGram.py
index 2526123..049da7d 100644
--- a/src/argaze/GazeAnalysis/NGram.py
+++ b/src/argaze/GazeAnalysis/NGram.py
@@ -36,7 +36,7 @@ class AOIScanPathAnalyzer(GazeFeatures.AOIScanPathAnalyzer):
         self.__ngrams_count = {}
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, aoi_scan_path: GazeFeatures.AOIScanPathType):
+    def analyze(self, timestamp: int|float, aoi_scan_path: GazeFeatures.AOIScanPathType):
 
         assert(len(aoi_scan_path) > 1)
 
diff --git a/src/argaze/GazeAnalysis/NearestNeighborIndex.py b/src/argaze/GazeAnalysis/NearestNeighborIndex.py
index 72df516..e42dea2 100644
--- a/src/argaze/GazeAnalysis/NearestNeighborIndex.py
+++ b/src/argaze/GazeAnalysis/NearestNeighborIndex.py
@@ -36,7 +36,7 @@ class ScanPathAnalyzer(GazeFeatures.ScanPathAnalyzer):
         self.__nearest_neighbor_index = 0
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, scan_path: GazeFeatures.ScanPathType):
+    def analyze(self, timestamp: int|float, scan_path: GazeFeatures.ScanPathType):
 
         assert(len(scan_path) > 1)
 
diff --git a/src/argaze/GazeAnalysis/TransitionMatrix.py b/src/argaze/GazeAnalysis/TransitionMatrix.py
index d001947..5248480 100644
--- a/src/argaze/GazeAnalysis/TransitionMatrix.py
+++ b/src/argaze/GazeAnalysis/TransitionMatrix.py
@@ -34,7 +34,7 @@ class AOIScanPathAnalyzer(GazeFeatures.AOIScanPathAnalyzer):
         self.__transition_matrix_density = 0.
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, aoi_scan_path: GazeFeatures.AOIScanPathType):
+    def analyze(self, timestamp: int|float, aoi_scan_path: GazeFeatures.AOIScanPathType):
 
         assert(len(aoi_scan_path) > 1)
 
diff --git a/src/argaze/GazeAnalysis/VelocityThresholdIdentification.py b/src/argaze/GazeAnalysis/VelocityThresholdIdentification.py
index 2c3ecd1..62f8bdd 100644
--- a/src/argaze/GazeAnalysis/VelocityThresholdIdentification.py
+++ b/src/argaze/GazeAnalysis/VelocityThresholdIdentification.py
@@ -143,7 +143,7 @@ class GazeMovementIdentifier(GazeFeatures.GazeMovementIdentifier):
         self.__saccade_positions = GazeFeatures.TimeStampedGazePositions()
 
     @DataFeatures.PipelineStepMethod
-    def identify(self, ts, gaze_position, terminate=False) -> GazeMovementType:
+    def identify(self, ts: int|float,  gaze_position, terminate=False) -> GazeMovementType:
 
         # Ignore non valid gaze position
         if not gaze_position.valid:
diff --git a/src/argaze/GazeFeatures.py b/src/argaze/GazeFeatures.py
index d70cdc6..db4c1f4 100644
--- a/src/argaze/GazeFeatures.py
+++ b/src/argaze/GazeFeatures.py
@@ -837,7 +837,7 @@ class ScanPathAnalyzer(DataFeatures.PipelineStepObject):
         return DataFeatures.DataDictionary(analysis)
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, scan_path: ScanPathType):
+    def analyze(self, timestamp: int|float, scan_path: ScanPathType):
         """Analyze scan path."""
 
         raise NotImplementedError('analyze() method not implemented')
@@ -1175,7 +1175,7 @@ class AOIScanPathAnalyzer(DataFeatures.PipelineStepObject):
         return DataFeatures.DataDictionary(analysis)
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, aoi_scan_path: AOIScanPathType):
+    def analyze(self, timestamp: int|float, aoi_scan_path: AOIScanPathType):
         """Analyze aoi scan path."""
 
         raise NotImplementedError('analyze() method not implemented')
diff --git a/src/argaze/PupillAnalysis/WorkloadIndex.py b/src/argaze/PupillAnalysis/WorkloadIndex.py
index 99f143b..1f3c586 100644
--- a/src/argaze/PupillAnalysis/WorkloadIndex.py
+++ b/src/argaze/PupillAnalysis/WorkloadIndex.py
@@ -34,7 +34,7 @@ class PupillDiameterAnalyzer(PupillFeatures.PupillDiameterAnalyzer):
         self.__last_ts = 0
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, ts, pupill_diameter) -> float:
+    def analyze(self, ts: int|float,  pupill_diameter) -> float:
         """Analyze workload index from successive timestamped pupill diameters."""
 
         # Ignore non valid pupill diameter
diff --git a/src/argaze/PupillFeatures.py b/src/argaze/PupillFeatures.py
index 8aa7827..d8f9331 100644
--- a/src/argaze/PupillFeatures.py
+++ b/src/argaze/PupillFeatures.py
@@ -83,7 +83,7 @@ class PupillDiameterAnalyzer(DataFeatures.PipelineStepObject):
     """Abstract class to define what should provide a pupill diameter analyser."""
 
     @DataFeatures.PipelineStepMethod
-    def analyze(self, ts, pupill_diameter) -> float:
+    def analyze(self, timestamp: int|float, pupill_diameter, float) -> float:
         """Analyze pupill diameter from successive timestamped pupill diameters."""
 
         raise NotImplementedError('analyze() method not implemented')
diff --git a/src/argaze/utils/demo_data/demo_gaze_analysis_setup.json b/src/argaze/utils/demo_data/demo_gaze_analysis_setup.json
index f921662..5f3e3c0 100644
--- a/src/argaze/utils/demo_data/demo_gaze_analysis_setup.json
+++ b/src/argaze/utils/demo_data/demo_gaze_analysis_setup.json
@@ -46,7 +46,8 @@
                     "n_max": 3
                 },
                 "Entropy":{}
-            }
+            },
+            "logging_module": "main_layer_logger.py"
         }
     },
     "image_parameters": {
@@ -107,5 +108,6 @@
             "color": [0, 255, 255],
             "size": 2
         }
-    }
+    },
+    "logging_module": "frame_logger.py"
 }
\ No newline at end of file
diff --git a/src/argaze/utils/demo_data/frame_logger.py b/src/argaze/utils/demo_data/frame_logger.py
new file mode 100644
index 0000000..f90e63f
--- /dev/null
+++ b/src/argaze/utils/demo_data/frame_logger.py
@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+
+""" """
+
+__author__ = "Théo de la Hogue"
+__credits__ = []
+__copyright__ = "Copyright 2023, Ecole Nationale de l'Aviation Civile (ENAC)"
+__license__ = "BSD"
+
+from argaze import ArFeatures, GazeFeatures, DataFeatures
+from argaze.utils import UtilsFeatures
+
+class FixationLogger(DataFeatures.PipelineStepObserver, UtilsFeatures.FileWriter):
+
+	def on_look(self, timestamp, frame):
+		"""Log fixations"""
+
+		#print(timestamp, "FixationLogger.on_look:", type(self), type(frame))
+
+		# Log fixations
+		if GazeFeatures.is_fixation(frame.gaze_movement) and frame.gaze_movement.finished:
+
+			log = (
+				timestamp, 
+				frame.gaze_movement.focus, 
+				frame.gaze_movement.duration, 
+				frame.layers['main_layer'].looked_aoi_name
+			)
+
+			self.write(log)
+
+class ScanPathAnalysisLogger(DataFeatures.PipelineStepObserver, UtilsFeatures.FileWriter):
+
+	def on_look(self, timestamp, frame):
+		"""Log scan path metrics"""
+
+		#print(timestamp, "ScanPathAnalysisLogger.on_look:", type(self), type(frame))
+
+		if frame.scan_path_analyzed:
+
+			log = (
+				timestamp, 
+				frame.scan_path_analyzers['argaze.GazeAnalysis.Basic'].path_duration, 
+				frame.scan_path_analyzers['argaze.GazeAnalysis.Basic'].steps_number, 
+				frame.scan_path_analyzers['argaze.GazeAnalysis.KCoefficient'].K, 
+				frame.scan_path_analyzers['argaze.GazeAnalysis.NearestNeighborIndex'].nearest_neighbor_index, 
+				frame.scan_path_analyzers['argaze.GazeAnalysis.ExploreExploitRatio'].explore_exploit_ratio
+			)
+
+			self.write(log)
+
+# Export loggers instances to register them as pipeline step object observer
+__loggers__ = {
+	"Fixation logger": FixationLogger(path="_export/logs/fixations.csv", header="Timestamp (ms), Focus (px), Duration (ms), AOI"),
+	"Scan path analysis logger": ScanPathAnalysisLogger(path="_export/logs/scan_path_metrics.csv", header="Timestamp (ms), Duration (ms), Step, K, NNI, XXR")
+	}
\ No newline at end of file
diff --git a/src/argaze/utils/demo_data/main_layer_logger.py b/src/argaze/utils/demo_data/main_layer_logger.py
new file mode 100644
index 0000000..e85dfcd
--- /dev/null
+++ b/src/argaze/utils/demo_data/main_layer_logger.py
@@ -0,0 +1,38 @@
+#!/usr/bin/env python
+
+""" """
+
+__author__ = "Théo de la Hogue"
+__credits__ = []
+__copyright__ = "Copyright 2023, Ecole Nationale de l'Aviation Civile (ENAC)"
+__license__ = "BSD"
+
+from argaze import ArFeatures, GazeFeatures
+from argaze.utils import UtilsFeatures
+
+from argaze import ArFeatures, GazeFeatures, DataFeatures
+from argaze.utils import UtilsFeatures
+
+class AOIScanPathAnalysisLogger(DataFeatures.PipelineStepObserver, UtilsFeatures.FileWriter):
+
+	def on_look(self, timestamp, layer):
+		"""Log aoi scan path metrics"""
+
+		#print(timestamp, "AOIScanPathAnalysisLogger.on_look:", type(self), type(layer))
+
+		if layer.aoi_scan_path_analyzed:
+
+			log = (
+				timestamp,
+				layer.aoi_scan_path_analyzers['argaze.GazeAnalysis.Basic'].path_duration, 
+				layer.aoi_scan_path_analyzers['argaze.GazeAnalysis.Basic'].steps_number, 
+				layer.aoi_scan_path_analyzers['argaze.GazeAnalysis.KCoefficient'].K, 
+				layer.aoi_scan_path_analyzers['argaze.GazeAnalysis.LempelZivComplexity'].lempel_ziv_complexity
+			)
+
+			self.write(log)
+
+# Export loggers instances to register them as pipeline step object observer
+__loggers__ = {
+	"AOI Scan path analysis logger": AOIScanPathAnalysisLogger(path="_export/logs/aoi_scan_path_metrics.csv", header="Timestamp (ms), Duration (ms), Step, K, LZC")
+	}
\ No newline at end of file
diff --git a/src/argaze/utils/demo_gaze_analysis_run.py b/src/argaze/utils/demo_gaze_analysis_run.py
index 9640d18..2dcc00e 100644
--- a/src/argaze/utils/demo_gaze_analysis_run.py
+++ b/src/argaze/utils/demo_gaze_analysis_run.py
@@ -37,14 +37,6 @@ def main():
     # Load ArFrame
     ar_frame = ArFeatures.ArFrame.from_json(args.frame)
 
-    # Bind to a frame layer
-    main_layer = ar_frame.layers['main_layer']
-
-    # Create FileWriter loggers
-    fixation_logger = UtilsFeatures.FileWriter(path="_export/logs/fixations.csv", header="Timestamp (ms), Focus (px), Duration (ms), AOI")
-    scan_path_logger = UtilsFeatures.FileWriter(path="_export/logs/scan_path_metrics.csv", header="Timestamp (ms), Duration (ms), Step, K, NNI, XXR")
-    aoi_scan_path_logger = UtilsFeatures.FileWriter(path="_export/logs/aoi_scan_path_metrics.csv", header="Timestamp (ms), Duration (ms), Step, K, LZC")
-
     # Create a window to display ArCamera
     cv2.namedWindow(ar_frame.name, cv2.WINDOW_AUTOSIZE)
 
@@ -70,45 +62,6 @@ def main():
 
             print('Gaze projection error:', e)
 
-        # Log fixations
-        if GazeFeatures.is_fixation(ar_frame.gaze_movement) and ar_frame.gaze_movement.finished:
-
-            log = (
-                timestamp, 
-                ar_frame.gaze_movement.focus, 
-                ar_frame.gaze_movement.duration, 
-                ar_frame.layers['main_layer'].looked_aoi_name
-            )
-
-            fixation_logger.write(log)
-
-        # Log scan path metrics
-        if ar_frame.scan_path_analyzed:
-
-            log = (
-                timestamp, 
-                ar_frame.scan_path_analyzers['argaze.GazeAnalysis.Basic'].path_duration, 
-                ar_frame.scan_path_analyzers['argaze.GazeAnalysis.Basic'].steps_number, 
-                ar_frame.scan_path_analyzers['argaze.GazeAnalysis.KCoefficient'].K, 
-                ar_frame.scan_path_analyzers['argaze.GazeAnalysis.NearestNeighborIndex'].nearest_neighbor_index, 
-                ar_frame.scan_path_analyzers['argaze.GazeAnalysis.ExploreExploitRatio'].explore_exploit_ratio
-            )
-
-            scan_path_logger.write(log)
-
-        # Log aoi scan path metrics
-        if main_layer.aoi_scan_path_analyzed:
-
-            log = (
-                timestamp,
-                main_layer.aoi_scan_path_analyzers['argaze.GazeAnalysis.Basic'].path_duration, 
-                main_layer.aoi_scan_path_analyzers['argaze.GazeAnalysis.Basic'].steps_number, 
-                main_layer.aoi_scan_path_analyzers['argaze.GazeAnalysis.KCoefficient'].K, 
-                main_layer.aoi_scan_path_analyzers['argaze.GazeAnalysis.LempelZivComplexity'].lempel_ziv_complexity
-            )
-
-            aoi_scan_path_logger.write(log)
-
     # Attach mouse callback to window
     cv2.setMouseCallback(ar_frame.name, on_mouse_event)