WIP: cattura in processo separato + close_stream (NON validata, sospesa)

backend/ambicatcher.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+"""ambicatcher — processo di cattura separato: scrive frame RGB grezzi su stdout.
+
+Vive in un processo a sé per due motivi:
+ 1) isolare GStreamer/PipeWire e dbus-python dal demone (che resta Python puro:
+    Gio per il D-Bus, numpy, pyserial);
+ 2) la sessione ScreenCast appartiene a QUESTO processo: quando termina, il portal
+    la chiude e l'indicatore "Trasmissione dello schermo" sparisce dal vassoio.
+
+Uso:
+    ambicatcher.py --leds 47 --rows 72 --sub 4 --fps 60
+Stampa una riga JSON di intestazione ({"node":..,"w":..,"h":..} oppure {"error":..})
+poi frame da (leds*sub) x rows pixel RGB, senza separatori.
+"""
+import argparse
+import json
+import os
+import signal
+import sys
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--leds", type=int, default=47)
+    ap.add_argument("--sub", type=int, default=4)
+    ap.add_argument("--rows", type=int, default=72)
+    ap.add_argument("--fps", type=int, default=60)
+    ap.add_argument("--drain", action="store_true",
+                    help="termina quando stdin si chiude (usato dal demone)")
+    a = ap.parse_args()
+
+    gw, gh = a.leds * a.sub, a.rows
+
+    def bye(*_):
+        raise SystemExit(0)
+
+    signal.signal(signal.SIGTERM, bye)
+    signal.signal(signal.SIGINT, bye)
+
+    out = sys.stdout.buffer
+    try:
+        from ambicapture import Capture, close_stream, screencast_stream
+
+        node, w, h = screencast_stream()
+        out.write((json.dumps({"node": node, "w": w, "h": h}) + "\n").encode())
+        out.flush()
+        cap = Capture(node, a.leds, sub=a.sub, rows=a.rows, fps=a.fps)
+        cap.start()
+    except Exception as e:
+        out.write((json.dumps({"error": f"{type(e).__name__}: {e}"}) + "\n").encode())
+        out.flush()
+        return 1
+
+    if a.drain:
+        import select
+        import threading
+
+        def watchdog():
+            # stdin chiuso dal padre = termina (e con noi la sessione portal)
+            try:
+                while True:
+                    if not sys.stdin.buffer.read(1):
+                        break
+            except Exception:
+                pass
+            os.kill(os.getpid(), signal.SIGTERM)
+
+        threading.Thread(target=watchdog, daemon=True).start()
+
+    try:
+        while True:
+            frame = cap.frame(200)
+            if frame is None:
+                continue
+            out.write(frame.tobytes())
+            out.flush()
+    except (BrokenPipeError, KeyboardInterrupt):
+        pass
+    finally:
+        try:
+            cap.stop()
+        except Exception:
+            pass
+        close_stream()
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())