playlist: Create a PlaylistSelection list model

This is a multi-selection model so we can do operations on multiple
tracks at once.

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

playlist/model.py

@@ -76,6 +76,16 @@ class FilterPlaylistModel(Gtk.FilterListModel):
         return sum([ int(self.get_item(i).length) for i in range(n) ])
 
 
+class PlaylistSelection(Gtk.MultiSelection):
+    def __init__(self):
+        Gtk.MultiSelection.__init__(self)
+        self.set_model(FilterPlaylistModel())
+
+    def get_filter_model(self): return self.get_model()
+    def get_playlist(self): return self.get_model().get_playlist()
+    def set_playlist(self, plist): return self.get_model().set_playlist(plist)
+
+
 class TagModel(GObject.GObject, Gio.ListModel):
     def __init__(self, tag=None):
         GObject.GObject.__init__(self)

playlist/test_model.py

@@ -118,6 +118,15 @@ class TestFilterPlaylistModel(unittest.TestCase):
         self.assertEqual(filter.get_runtime(), 1)
 
 
+class TestPlaylistSelectionModel(unittest.TestCase):
+    def test_init(self):
+        selection = model.PlaylistSelection()
+        self.assertIsInstance(selection, Gtk.MultiSelection)
+        self.assertIsInstance(selection.get_model(), model.FilterPlaylistModel)
+        self.assertEqual(selection.get_filter_model(), selection.get_model())
+        self.assertIsNone(selection.get_playlist())
+
+
 class TestTagModel(unittest.TestCase):
     def setUp(self):
         self.changed = (None, None, None)