Overlay collate

holoviews/core/layout.py

@@ -366,10 +366,6 @@ def relabel_item_paths(cls, items):
         return list(zip(paths, path_items))
 
 
-    @classmethod
-    def _from_values(cls, val):
-        return reduce(lambda x,y: x+y, val).display('auto')
-
     @classmethod
     def from_values(cls, val):
         """
@@ -379,15 +375,20 @@ def from_values(cls, val):
         collection = isinstance(val, (list, tuple))
         if type(val) is cls:
             return val
-        elif collection and len(val)>1:
-            return cls._from_values(val)
-        elif collection:
-            val = val[0]
-        group = group_sanitizer(val.group)
-        group = ''.join([group[0].upper(), group[1:]])
-        label = label_sanitizer(val.label if val.label else 'I')
-        label = ''.join([label[0].upper(), label[1:]])
-        return cls(items=[((group, label), val)])
+        elif not collection:
+            val = [val]
+        paths, items = [], []
+        count = 2
+        for v in val:
+            group = group_sanitizer(v.group)
+            group = ''.join([group[0].upper(), group[1:]])
+            label = label_sanitizer(v.label if v.label else 'I')
+            label = ''.join([label[0].upper(), label[1:]])
+            new_path, count = cls.new_path((group, label), v, paths, count)
+            new_path = tuple(''.join((p[0].upper(), p[1:])) for p in new_path)
+            paths.append(new_path)
+            items.append((new_path, v))
+        return cls(items=items)
 
 
     def __init__(self, items=None, identifier=None, parent=None, **kwargs):

holoviews/core/overlay.py

@@ -149,6 +149,14 @@ def __mul__(self, other):
         return Overlay(items=self.relabel_item_paths(items)).display('all')
 
 
+    def collate(self):
+        """
+        Collates any objects in the Overlay resolving any issues
+        the recommended nesting structure.
+        """
+        return reduce(lambda x,y: x*y, self.values())
+
+
     def collapse(self, function):
         """
         Collapses all the Elements in the Overlay using the

holoviews/plotting/util.py

@@ -4,7 +4,7 @@
 import param
 
 from ..core import (HoloMap, DynamicMap, CompositeOverlay, Layout,
-                    GridSpace, NdLayout, Store)
+                    GridSpace, NdLayout, Store, Overlay)
 from ..core.util import (match_spec, is_number, wrap_tuple, basestring,
                          get_overlay_spec, unique_iterator, safe_unicode)
 
@@ -14,6 +14,9 @@ def displayable(obj):
     Predicate that returns whether the object is displayable or not
     (i.e whether the object obeys the nesting hierarchy
     """
+    if isinstance(obj, Overlay) and any(isinstance(o, (HoloMap, GridSpace))
+                                        for o in obj):
+        return False
     if isinstance(obj, HoloMap):
         return not (obj.type in [Layout, GridSpace, NdLayout])
     if isinstance(obj, (GridSpace, Layout, NdLayout)):
@@ -28,6 +31,16 @@ class Warning(param.Parameterized): pass
 display_warning = Warning(name='Warning')
 
 def collate(obj):
+    if isinstance(obj, Overlay):
+        nested_type = [type(o).__name__ for o in obj
+                       if isinstance(o, (HoloMap, GridSpace))][0]
+        display_warning.warning("Nesting %ss within an Overlay makes it difficult "
+                                "to access your data or control how it appears; "
+                                "we recommend calling .collate() on the Overlay "
+                                "in order to follow the recommended nesting "
+                                "structure shown in the Composing Data tutorial"
+                                "(http://git.io/vtIQh)" % nested_type)
+        return obj.collate()
     if isinstance(obj, HoloMap):
         display_warning.warning("Nesting %ss within a HoloMap makes it difficult "
                                 "to access your data or control how it appears; "

tests/testcollation.py

@@ -7,10 +7,12 @@
 
 import numpy as np
 
-from holoviews.core import Collator, HoloMap, NdOverlay
+from holoviews.core import Collator, HoloMap, NdOverlay, Overlay, GridSpace
 from holoviews.element import Curve
+from holoviews.element.comparison import ComparisonTestCase
 
-class TestCollation(unittest.TestCase):
+
+class TestCollation(ComparisonTestCase):
     def setUp(self):
         alphas, betas, deltas = 2, 2, 2
         Bs = list(range(100))
@@ -67,3 +69,14 @@ def test_collate_layout_hmap(self):
         collated = collated()
         self.assertEqual(repr(collated), repr(layout))
         self.assertEqual(collated.dimensions(), layout.dimensions())
+
+    def test_overlay_hmap_collate(self):
+        hmap = HoloMap({i: Curve(np.arange(10)*i) for i in range(3)})
+        overlaid = Overlay([hmap, hmap, hmap]).collate()
+        self.assertEqual(overlaid, hmap*hmap*hmap)
+
+    def test_overlay_gridspace_collate(self):
+        grid = GridSpace({(i,j): Curve(np.arange(10)*i) for i in range(3)
+                          for j in range(3)})
+        overlaid = Overlay([grid, grid, grid]).collate()
+        self.assertEqual(overlaid, grid*grid*grid)