Add song progress bar

heos.py

@@ -43,6 +43,11 @@ class HeosClient:
         self._sock = None
         self._buffer = b""
         self._lock = threading.Lock()
+        # pid -> {"cur_pos", "duration"}, filled in from whatever
+        # unsolicited progress events turn up while we are reading the
+        # reply to some other command. Dropped on reconnect, since a gap
+        # in the connection is a gap in what we know.
+        self._progress = {}
 
     # -- connection management -----------------------------------------
     def _connect(self):
@@ -51,6 +56,14 @@ class HeosClient:
         sock.settimeout(self.timeout)
         self._sock = sock
         self._buffer = b""
+        self._progress = {}
+        # Without this, HEOS never pushes the now-playing-progress events
+        # that _exchange() below watches for. Best-effort: a player that
+        # refuses it still works, it just never shows song progress.
+        try:
+            self._exchange("system/register_for_change_events", {"enable": "on"})
+        except (OSError, HeosError):
+            pass
 
     def _close(self):
         if self._sock is not None:
@@ -106,6 +119,7 @@ class HeosClient:
             heos = reply.get("heos", {})
 
             if heos.get("command") != path:
+                self._watch_progress(heos)
                 continue  # an event or a late reply to something else
             if "under process" in heos.get("message", ""):
                 continue  # placeholder ack; the real payload follows
@@ -113,6 +127,30 @@ class HeosClient:
                 raise HeosError(_failure_text(heos))
             return reply
 
+    def _watch_progress(self, heos: dict):
+        """Skims a passing player_now_playing_progress event for its
+        pid/cur_pos/duration, the only source of song-position data this
+        client has -- there is no dedicated listener, so this only catches
+        what happens to arrive while some other command is being read."""
+        if heos.get("command") != "event/player_now_playing_progress":
+            return
+        message = parse_message(heos.get("message", ""))
+        pid = message.get("pid")
+        if not pid:
+            return
+        try:
+            self._progress[pid] = {
+                "cur_pos": int(message.get("cur_pos", 0)),
+                "duration": int(message.get("duration", 0)),
+            }
+        except ValueError:
+            pass
+
+    def progress_for(self, pid) -> dict:
+        """{"cur_pos", "duration"} in ms for a player, or None if no
+        progress event for it has come through yet this connection."""
+        return self._progress.get(str(pid))
+
     def heart_beat(self):
         """Keep the socket warm so the first press after an idle spell is
         as fast as the rest."""