libsaria: Test song visibility through sources

It queries the library, but the playlist and the queue should be able to
use this too.  Then they don't each need to track what is currently
visible.

libsaria/sources/__init__.py

@@ -41,6 +41,9 @@ def get_attrs(*attrs):
 		return library.get_attrs(cur_id, *attrs)
 	return -1
 
+def is_visible(id):
+	return library.is_visible(id)
+
 def set_attr(attr, value):
 	if cur_source:
 		cur_source.set_attr(cur_id, attr, value)

libsaria/sources/library/__init__.py

@@ -6,9 +6,11 @@ import tree
 import index
 
 # Function pointers for conveniance
-add_path  = library.add_path
-get_attrs = library.get_attrs
-list_ids  = tree.list_ids
+add_path   = library.add_path
+get_attrs  = library.get_attrs
+list_ids   = tree.list_ids
+filter     = index.filter
+is_visible = index.is_visible
 
 library.load()
 tree.make_tree()

libsaria/sources/library/index.py

@@ -5,6 +5,7 @@ import library
 
 lib_index = dict()
 all_ids   = set()
+matching  = set()
 
 space_ord = ord(" ")
 stripc    = u"\"#$%&'*+<=>@[]^`{|}~.?!"
@@ -40,3 +41,9 @@ def add_tracks(tracks):
 def reindex():
 	for src, tracks in library.lib_dict.iteritems():
 		add_tracks(tracks)
+
+def is_visible(id):
+	return id in matching
+
+def filter(text):
+	print text