refactor: simplify Session initialization and update stats display logic

app.py

@@ -7,12 +7,12 @@ import os
 import psutil
 
 class Session:
-    def __init__(self, id: str, latest_frame: MatLike, measured_fps: float, cpu_usage: float, show_fps: bool):
+    def __init__(self, id: str):
         self.id = id
-        self.latest_frame: MatLike = latest_frame
-        self.measured_fps = measured_fps
-        self.cpu_usage = cpu_usage
-        self.show_fps = show_fps
+        self.latest_frame: MatLike = None
+        self.measured_fps = 0
+        self.cpu_usage = 0
+        self.show_stats = os.environ.get("SHOW_STATS", "0") == "1"
 
 app = Flask(__name__)
 PORT = int(os.environ.get("PORT", 5000))
@@ -53,18 +53,22 @@ def frame_processor(session_id: str):
                 cap.set(cv2.CAP_PROP_POS_FRAMES, 0)
                 continue
             else:
-                if session.show_fps:
+                if session.show_stats:
                     font = cv2.FONT_HERSHEY_SIMPLEX
                     font_scale = 1
                     thickness = 2
                     color = (0, 255, 0)
-                    text = f"ID: {session_id}\n FPS: {session.measured_fps:.0f}\n CPU: {session.cpu_usage:02.0f}%"
+                    text =f"""
+                    ID: {session_id}
+                    FPS: {session.measured_fps:.0f}
+                    CPU: {session.cpu_usage:02.0f}%
+                    """
 
                     y0, dy = 30, 36
                     for i, line in enumerate(text.split('\n')):
                         (text_width, text_height), _ = cv2.getTextSize(line, font, font_scale, thickness)
                         x = frame.shape[1] - text_width - 10
-                        y = y0 + i*dy
+                        y = y0 + (i - 1) * dy
                         cv2.putText(frame, line, (x, y), font, font_scale, color, thickness, cv2.LINE_AA)
 
             # control framerate
@@ -100,7 +104,7 @@ def video_feed():
     session_id = request.args.get("id", "default")
 
     if session_id not in [s.id for s in sessions]:
-        session = Session(session_id, None, 0, 0, True)
+        session = Session(session_id)
         sessions.add(session)
         threading.Thread(target=frame_processor, args=[session_id], daemon=True).start()