Fix the grid layout helper.

enable/constraints_container.py

@@ -197,16 +197,16 @@ def _content_box_constraints(self):
         contents_top = cns.contents_top
         contents_bottom = cns.contents_bottom
 
-        # Add these to the namespace, but don't use them
+        # Add these to the namespace, but don't use them here
         cns.contents_width = contents_right - contents_left
         cns.contents_height = contents_top - contents_bottom
         cns.contents_v_center = contents_bottom + cns.contents_height / 2.0
         cns.contents_h_center = contents_left + cns.contents_width / 2.0
 
-        return [contents_left == cns.left + self.padding_left,
-                contents_bottom == cns.bottom + self.padding_bottom,
-                contents_right == cns.right - self.padding_right,
-                contents_top == cns.top - self.padding_top,
+        return [contents_left == cns.left,
+                contents_bottom == cns.bottom,
+                contents_right == cns.left + cns.width,
+                contents_top == cns.bottom + cns.height,
             ]
 
     def _update_fixed_constraints(self):

enable/layout/debug_constraints.py

@@ -57,7 +57,7 @@ def update_from_constraints(self, layout_mgr):
 
         """
         self.boxes = defaultdict(Coords)
-        if layout_mgr is not None:
+        if layout_mgr is not None and layout_mgr._constraints:
             for constraint in layout_mgr._constraints:
                 for expr in (constraint.lhs, constraint.rhs):
                     for term in expr.terms:

enable/layout/layout_helpers.py

@@ -670,19 +670,19 @@ def _get_constraints(self, component):
 
         # Add some neighbor relations to the row and column vars.
         for r1, r2 in zip(row_vars[:-1], row_vars[1:]):
-            constraints.append(r1 <= r2)
+            constraints.append(r1 >= r2)
         for c1, c2 in zip(col_vars[:-1], col_vars[1:]):
             constraints.append(c1 <= c2)
 
         # Setup the initial interior bounding box for the grid.
         margins = self.margins
-        top_items = (self.top, EqSpacer(margins.top), row_vars[0])
-        bottom_items = (row_vars[-1], EqSpacer(margins.bottom), self.bottom)
+        bottom_items = (self.bottom, EqSpacer(margins.bottom), row_vars[-1])
+        top_items = (row_vars[0], EqSpacer(margins.top), self.top)
         left_items = (self.left, EqSpacer(margins.left), col_vars[0])
         right_items = (col_vars[-1], EqSpacer(margins.right), self.right)
         helpers = [
-            AbutmentHelper('vertical', *top_items),
             AbutmentHelper('vertical', *bottom_items),
+            AbutmentHelper('vertical', *top_items),
             AbutmentHelper('horizontal', *left_items),
             AbutmentHelper('horizontal', *right_items),
         ]
@@ -976,7 +976,7 @@ class AbutmentConstraintFactory(SequenceConstraintFactory):
     #: lookup for a pair of items in order to make the constraint.
     orientation_map = {
         'horizontal': ('right', 'left'),
-        'vertical': ('bottom', 'top'),
+        'vertical': ('top', 'bottom'),
     }
 
     @classmethod
@@ -1018,6 +1018,8 @@ def from_items(cls, items, orientation, spacing):
                    "'horizontal'. Got %r instead.")
             raise ValueError(msg % orientation)
         first_name, second_name = orient
+        if orientation == 'vertical':
+            items.reverse()
         return cls._make_cns(items, first_name, second_name, spacing)
 
 

examples/enable/constraints_demo.py

@@ -1,6 +1,6 @@
 
 from enable.api import Component, ComponentEditor, ConstraintsContainer
-from enable.layout.layout_helpers import hbox, align, grid
+from enable.layout.layout_helpers import hbox, vbox, align, grid, horizontal
 from traits.api import HasTraits, Any, Instance, List, Property
 from traitsui.api import Item, View, HGroup, TabularEditor
 from traitsui.tabular_adapter import TabularAdapter
@@ -55,17 +55,20 @@ def _canvas_default(self):
 
         parent.add(one, two, three, four)
         parent.layout_constraints = [
-            hbox(one.constraints, two.constraints,
-                 three.constraints, four.constraints),
+            grid([one.constraints, two.constraints],
+                 [three.constraints, four.constraints]),
+            align('height', one.constraints, two.constraints,
+                           three.constraints, four.constraints),
             align('width', one.constraints, two.constraints,
                            three.constraints, four.constraints),
-
         ]
 
         return parent
 
     def _get_constraints(self):
-        return list(self.canvas._layout_manager._constraints)
+        if self.canvas._layout_manager._constraints:
+            return list(self.canvas._layout_manager._constraints)
+        return []
 
     def _selected_constraints_changed(self, new):
         if new is None or new == []: