lib: Give Tags a get_header() function

The sidebar will want this for giving header widgets to some rows

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

lib/tag.py

@@ -46,6 +46,9 @@ class Tag:
             self.tracks.append(track)
         self.TrackAdded.publish(self, track)
 
+    def get_header(self):
+        return self.sort[0].upper() if len(self.sort) > 0 else ""
+
     def init_track(self, track):
         with self.lock:
             try:

lib/test_tag.py

@@ -48,6 +48,11 @@ class TestTag(unittest.TestCase):
         self.assertTrue(b < a2)
         self.assertTrue(a2 < c)
 
+    def test_tag_header(self):
+        self.assertEqual(tag.Tag("Test").get_header(), "T")
+        self.assertEqual(tag.Tag("Test", "sort").get_header(), "S")
+        self.assertEqual(tag.Tag("").get_header(), "")
+
     def test_tag_state(self):
         t = tag.Tag("test")
         tracks = [ FakeTrack(i) for i in range(5) ]