Add "showtime" example client

Closes #20.

Author: mgeier

doc/examples.rst

@@ -17,6 +17,13 @@ Pass-Through Client
 
 .. literalinclude:: ../examples/thru_client.py
 
+"Showtime" Client
+-----------------
+
+:download:`showtime.py <../examples/showtime.py>`
+
+.. literalinclude:: ../examples/showtime.py
+
 MIDI Monitor
 ------------
 

examples/showtime.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+
+"""Display information about time, transport state et cetera.
+
+This is somewhat modeled after the "showtime.c" example of JACK.
+https://github.com/jackaudio/example-clients/blob/master/showtime.c
+https://github.com/jackaudio/jack2/blob/master/example-clients/showtime.c
+
+"""
+from contextlib import suppress
+import time
+import sys
+
+import jack
+
+
+try:
+    client = jack.Client('showtime')
+except jack.JackError:
+    sys.exit('JACK server not running?')
+
+
+def showtime():
+    state, pos = client.transport_query()
+    items = []
+    items.append('frame = {}  frame_time = {} usecs = {} '.format(
+        pos['frame'], client.frame_time, pos['usecs']))
+    items.append('state: {}'.format(state))
+    with suppress(KeyError):
+        items.append('BBT: {bar:3}|{beat}|{tick:04}'.format(**pos))
+    with suppress(KeyError):
+        items.append('TC: ({frame_time:.6f}, {next_time:.6f})'.format(**pos))
+    with suppress(KeyError):
+     	items.append('BBT offset: ({bbt_offset})'.format(**pos))
+    with suppress(KeyError):
+     	items.append(
+            'audio/video: ({audio_frames_per_video_frame})'.format(**pos))
+    with suppress(KeyError):
+        video_offset = pos['video_offset']
+        if video_offset:
+            items.append(' video@: ({})'.format(video_offset))
+        else:
+            items.append(' no video');
+    print(*items, sep='\t')
+
+
+@client.set_shutdown_callback
+def shutdown(status, reason):
+    sys.exit('JACK shut down, exiting ...')
+
+
+with client:
+    try:
+        while True:
+            time.sleep(0.00002)
+            showtime()
+    except KeyboardInterrupt:
+        print('signal received, exiting ...', file=sys.stderr)
+        sys.exit(0)