Do not 'compute' most initial values.

weasy/css/__init__.py

@@ -40,6 +40,7 @@ function for each step:
 
 """
 
+import re
 import logging
 
 from lxml import cssselect
@@ -73,6 +74,11 @@ PAGE_PSEUDOCLASS_SPECIFICITY = {
     ':first': 10,
 }
 
+# A test function that returns True if the given property name has an
+# initial value that is not always the same when computed.
+RE_INITIAL_NOT_COMPUTED = re.compile(
+    '^(display|border_[a-z]+_(width|color))$').match
+
 
 class StyleDict(object):
     """A mapping (dict-like) that allows attribute access to values.
@@ -450,9 +456,10 @@ def computed_from_cascaded(element, cascaded, parent_style, pseudo_type=None):
             keyword = 'initial'
 
         if keyword == 'initial':
-            # Some initial values are the same when computed.
-            # TODO: Add them to the ``computed`` dict?
             value = initial
+            if not RE_INITIAL_NOT_COMPUTED(name):
+                # The value is the same as when computed
+                computed[name] = value
         elif keyword == 'inherit':
             value = parent_style[name]
             # Values in parent_style are already computed.

weasy/css/computed_values.py

@@ -63,6 +63,7 @@ BORDER_WIDTH_KEYWORDS = {
     'medium': 3,
     'thick': 5,
 }
+assert INITIAL_VALUES['border_top_width'] == BORDER_WIDTH_KEYWORDS['medium']
 
 # http://www.w3.org/TR/CSS21/fonts.html#propdef-font-weight
 FONT_WEIGHT_RELATIVE = dict(

weasy/css/properties.py

@@ -45,10 +45,10 @@ INITIAL_VALUES = {
     'border_right_style': 'none',
     'border_bottom_style': 'none',
     'border_left_style': 'none',
-    'border_top_width': 'medium',
-    'border_right_width': 'medium',
-    'border_bottom_width': 'medium',
-    'border_left_width': 'medium',
+    'border_top_width': 3,  # Computed value for 'medium'
+    'border_right_width': 3,
+    'border_bottom_width': 3,
+    'border_left_width': 3,
     'bottom': 'auto',
     'caption_side': 'top',
     'clear': 'none',

weasy/tests/test_css_properties.py

@@ -97,7 +97,7 @@ def test_expand_borders():
         'border_top_color': 'red',
     }
     assert expand_to_dict('border_top', 'solid') == {
-        'border_top_width': 'medium',
+        'border_top_width': 3,
         'border_top_style': 'solid',
         'border_top_color': 'currentColor',
     }