From d284fb7a137d69f2a846a2d7e08cd4aaa5233ef8 Mon Sep 17 00:00:00 2001
From: pacien
Date: Thu, 7 Sep 2017 10:01:59 +0200
Subject: Add unique mpv instance management script

---
 umpv | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100755 umpv

diff --git a/umpv b/umpv
new file mode 100755
index 0000000..0080b44
--- /dev/null
+++ b/umpv
@@ -0,0 +1,97 @@
+#!/usr/bin/env python
+
+"""
+This script emulates "unique application" functionality on Linux. When starting
+playback with this script, it will try to reuse an already running instance of
+mpv (but only if that was started with umpv). Other mpv instances (not started
+by umpv) are ignored, and the script doesn't know about them.
+
+This only takes filenames as arguments. Custom options can't be used; the script
+interprets them as filenames. If mpv is already running, the files passed to
+umpv are appended to mpv's internal playlist. If a file does not exist or is
+otherwise not playable, mpv will skip the playlist entry when attempting to
+play it (from the GUI perspective, it's silently ignored).
+
+If mpv isn't running yet, this script will start mpv and let it control the
+current terminal. It will not write output to stdout/stderr, because this
+will typically just fill ~/.xsession-errors with garbage.
+
+mpv will terminate if there are no more files to play, and running the umpv
+script after that will start a new mpv instance.
+
+Note that you can control the mpv instance by writing to the command fifo:
+
+    echo "cycle fullscreen" > ~/.umpv_fifo
+
+Note: you can supply custom mpv path and options with the MPV environment
+      variable. The environment variable will be split on whitespace, and the
+      first item is used as path to mpv binary and the rest is passed as options
+      _if_ the script starts mpv. If mpv is not started by the script (i.e. mpv
+      is already running), this will be ignored.
+"""
+
+import sys
+import os
+import errno
+import subprocess
+import fcntl
+import stat
+import string
+
+files = sys.argv[1:]
+
+# this is the same method mpv uses to decide this
+def is_url(filename):
+    parts = filename.split("://", 1)
+    if len(parts) < 2:
+        return False
+    # protocol prefix has no special characters => it's an URL
+    allowed_symbols = string.ascii_letters + string.digits + '_'
+    prefix = parts[0]
+    return all(map(lambda c: c in allowed_symbols, prefix))
+
+# make them absolute; also makes them safe against interpretation as options
+def make_abs(filename):
+    if not is_url(filename):
+        return os.path.abspath(filename)
+    return filename
+files = [make_abs(f) for f in files]
+
+FIFO = os.path.join(os.getenv("HOME"), ".umpv_fifo")
+
+fifo_fd = -1
+try:
+    fifo_fd = os.open(FIFO, os.O_NONBLOCK | os.O_WRONLY)
+except OSError as e:
+    if e.errno == errno.ENXIO:
+        pass  # pipe has no writer
+    elif e.errno == errno.ENOENT:
+        pass # doesn't exist
+    else:
+        raise e
+
+if fifo_fd >= 0:
+    # Unhandled race condition: what if mpv is terminating right now?
+    fcntl.fcntl(fifo_fd, fcntl.F_SETFL, 0) # set blocking mode
+    fifo = os.fdopen(fifo_fd, "w")
+    for f in files:
+        # escape: \ \n "
+        f = f.replace("\\", "\\\\").replace("\"", "\\\"").replace("\n", "\\n")
+        f = "\"" + f + "\""
+        fifo.write("raw loadfile " + f + " append\n")
+else:
+    # Recreate pipe if it doesn't already exist.
+    # Also makes sure it's safe, and no other user can create a bogus pipe
+    # that breaks security.
+    try:
+        os.unlink(FIFO)
+    except OSError as e:
+        pass
+    os.mkfifo(FIFO, 0o600)
+
+    opts = (os.getenv("MPV") or "mpv").split()
+    opts.extend(["--no-terminal", "--force-window", "--input-file=" + FIFO,
+                 "--"])
+    opts.extend(files)
+
+    subprocess.check_call(opts)
-- 
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