i3-companion: use new protocol format

It's simple enough and I don't want to spawn a polybar-msg. Maybe at a
later point, we may be smarter. The problem with the old socket is
that if you send messages fast enough on it, polybar may believe they
are one message since it is not length-encoded on its side and it's a
simple FIFO file (so no message boundaries). Dunno why I didn't get a
problem until now.

bin/i3-companion

@@ -17,6 +17,7 @@ import shlex
 import subprocess
 import sys
 import types
+import struct
 
 import i3ipc
 from i3ipc.aio import Connection
@@ -263,14 +264,22 @@ def polybar(module):
                 out.write(content)
 
             # Send it to polybar
-            for name in glob.glob("/tmp/polybar_mqueue.*"):
+            cmd = bytes(f"#{module}.send.{content}", "utf-8")
+            data = b"polyipc" + struct.pack("=BIB", 0, len(cmd), 2) + cmd
+            for name in glob.glob(f"{os.getenv('XDG_RUNTIME_DIR')}/polybar/*.sock"):
                 try:
-                    with open(os.open(name, os.O_WRONLY | os.O_NONBLOCK), "w") as out:
-                        cmd = f"action:#{module}.send.{content}"
-                        out.write(cmd)
+                    reader, writer = await asyncio.open_unix_connection(name)
                 except OSError as e:
                     if e.errno != errno.ENXIO:
                         raise
+                else:
+                    try:
+                        writer.write(data)
+                        await writer.drain()
+                        await reader.read()
+                    finally:
+                        writer.close()
+                        await writer.wait_closed()
 
             logger.info(f"polybar/{module}: content updated")
             cache[module] = content