fixes issue #87

pyface/tasks/task_layout.py

@@ -3,7 +3,7 @@
 import sys
 
 # Enthought library imports.
-from traits.api import Either, Enum, HasStrictTraits, Int, List, Str, This
+from traits.api import Either, Enum, HasStrictTraits, Int, Instance, List, Str, This
 
 
 class LayoutItem(HasStrictTraits):
@@ -132,7 +132,8 @@ class Splitter(LayoutContainer):
 
     # The sub-items of the splitter, which are PaneItems, Tabbed layouts, and
     # other Splitters.
-    items = List(Either(PaneItem, Tabbed, This), pretty_skip=True)
+    items = List(Either(PaneItem, Tabbed,
+                        Instance('pyface.tasks.api.Splitter')), pretty_skip=True)
 
 class HSplitter(Splitter):
     """ A convenience class for horizontal splitters.

pyface/tasks/tests/test_task_layout.py

@@ -0,0 +1,35 @@
+# Standard library imports.
+import unittest
+
+# Enthought library imports.
+from pyface.tasks.api import HSplitter, PaneItem, Tabbed, VSplitter
+
+
+class LayoutItemsTestCase(unittest.TestCase):
+    """ Testing that the layout types play nice with each other.
+
+    This is a regression test for issue #87
+    (https://github.com/enthought/pyface/issues/87)
+
+    """
+
+    def setUp(self):
+        self.items = [HSplitter(), PaneItem(), Tabbed(), VSplitter()]
+
+    def test_hsplitter_items(self):
+        layout = HSplitter(*self.items)
+        self.assertEqual(layout.items, self.items)
+
+    def test_tabbed_items(self):
+        # Tabbed items only accept PaneItems
+        items = [PaneItem(), PaneItem()]
+        layout = Tabbed(*items)
+        self.assertEqual(layout.items, items)
+
+    def test_vsplitter_items(self):
+        layout = VSplitter(*self.items)
+        self.assertEqual(layout.items, self.items)
+
+
+if __name__ == '__main__':
+    unittest.main()