libsaria: Fix playlist num_visible()

When the playlist is changed, I need to test song ids against the
visible set to get the correct number

libsaria/sources/playlist/__init__.py

@@ -6,12 +6,26 @@ import next
 
 # Function pointers for convenience
 add_ids = playlist.add_ids
-rm_ids  = playlist.rm_ids
-reset   = playlist.reset
 
 playlist.load()
 visible = playlist.as_set()
 
+def add_ids(ids):
+	for id in ids:
+		if libsaria.sources.is_visible(id):
+			visible.add(id)
+	playlist.add_ids(ids)
+
+def rm_ids(ids):
+	global visible
+	visible = visible - set(ids)
+	playlist.rm_ids(ids)
+
+def reset():
+	global visible
+	visible = set()
+	playlist.reset()
+
 def list_ids():
 	for id in playlist.song_list:
 		yield id