Simplify the handling of 'auto' lengths.

weasyprint/css/computed_values.py

@@ -256,6 +256,8 @@ def length_tuple(computer, name, values):
 @register_computer('text-indent')
 def length(computer, name, value, font_size=None, pixels_only=False):
     """Compute a length ``value``."""
+    if value == 'auto':
+        return value
     if value.value == 0:
         return 0 if pixels_only else ZERO_PIXELS
 

weasyprint/css/properties.py

@@ -19,12 +19,6 @@ from tinycss.color3 import COLOR_KEYWORDS
 Dimension = collections.namedtuple('Dimension', ['value', 'unit'])
 
 
-class _Auto(str):
-    unit = None
-    value = 'auto'
-AUTO = _Auto('auto')  # for values that can be 'auto' as well as a dimension
-
-
 # See http://www.w3.org/TR/CSS21/propidx.html
 INITIAL_VALUES = {
     'background_attachment': 'scroll',
@@ -34,7 +28,7 @@ INITIAL_VALUES = {
     'background_repeat': 'repeat',
     'background_clip': 'border-box',  # CSS3
     'background_origin': 'padding-box',  # CSS3
-    'background_size': (AUTO, AUTO),  # CSS3
+    'background_size': ('auto', 'auto'),  # CSS3
     'border_collapse': 'separate',
     # http://www.w3.org/TR/css3-color/#currentcolor
     'border_top_color': 'currentColor',
@@ -50,7 +44,7 @@ INITIAL_VALUES = {
     'border_right_width': 3,
     'border_bottom_width': 3,
     'border_left_width': 3,
-    'bottom': AUTO,
+    'bottom': 'auto',
     'caption_side': 'top',
     'clear': 'none',
     'clip': (),  # empty collection, computed value for 'auto'
@@ -71,8 +65,8 @@ INITIAL_VALUES = {
     'font_style': 'normal',
     'font_variant': 'normal',
     'font_weight': 400,
-    'height': AUTO,
-    'left': AUTO,
+    'height': 'auto',
+    'left': 'auto',
     'letter_spacing': 'normal',
     'line_height': 'normal',
     'list_style_image': 'none',
@@ -100,20 +94,20 @@ INITIAL_VALUES = {
     'page_break_inside': 'auto',
     'quotes': list('“”‘’'),  # depends on user agent
     'position': 'static',
-    'right': AUTO,
+    'right': 'auto',
     'table_layout': 'auto',
     'text_align': '-weasy-start',  # Taken from CSS3 Text.
                    # The only other supported value form CSS3 is -weasy-end.
     'text_decoration': 'none',
     'text_indent': Dimension(0, 'px'),
     'text_transform': 'none',
-    'top': AUTO,
+    'top': 'auto',
     'unicode_bidi': 'normal',
     'vertical_align': 'baseline',
     'visibility': 'visible',
     'white_space': 'normal',
     'widows': 2,
-    'width': AUTO,
+    'width': 'auto',
     'word_spacing': 0,  # computed value for 'normal'
     'z_index': 'auto',
 

weasyprint/css/validation.py

@@ -22,7 +22,7 @@ from ..logger import LOGGER
 from ..formatting_structure import counters
 from ..compat import urljoin
 from .properties import (INITIAL_VALUES, KNOWN_PROPERTIES, NOT_PRINT_MEDIA,
-                         AUTO, Dimension)
+                         Dimension)
 from . import computed_values
 
 # TODO: unit-test these validators
@@ -253,15 +253,15 @@ def background_size(tokens):
         if keyword in ('contain', 'cover'):
             return keyword
         if keyword == 'auto':
-            return (AUTO, AUTO)
+            return ('auto', 'auto')
         length = get_length(token, negative=False)
         if length:
-            return (length, AUTO)
+            return (length, 'auto')
     elif len(tokens) == 2:
         values = []
         for token in tokens:
             if get_keyword(token) == 'auto':
-                values.append(AUTO)
+                values.append('auto')
             else:
                 length = get_length(token, negative=False)
                 if length:
@@ -341,7 +341,7 @@ def clip(token):
             values = []
             for arg in args:
                 if get_keyword(arg) == 'auto':
-                    values.append(AUTO)
+                    values.append('auto')
                 else:
                     length = get_length(arg)
                     if length:
@@ -465,7 +465,7 @@ def lenght_precentage_or_auto(token, negative=True):
     if length:
         return length
     if get_keyword(token) == 'auto':
-        return AUTO
+        return 'auto'
 
 
 @validator('height')

weasyprint/layout/percentages.py

@@ -15,8 +15,7 @@ from __future__ import division, unicode_literals
 from ..formatting_structure import boxes
 
 
-def resolve_one_percentage(box, property_name, refer_to,
-                           allowed_keywords=None):
+def resolve_one_percentage(box, property_name, refer_to):
     """Set a used length value from a computed length value.
 
     ``refer_to`` is the length for 100%. If ``refer_to`` is not a number, it
@@ -25,21 +24,13 @@ def resolve_one_percentage(box, property_name, refer_to,
     """
     # box.style has computed values
     value = box.style[property_name]
-    if value.unit == 'px':
+    if value == 'auto':
+        result = value
+    elif value.unit == 'px':
         result = value.value
     else:
-        if value.unit == '%':
-            if isinstance(refer_to, (int, float)):
-                # A percentage
-                result = value.value * refer_to / 100.
-            else:
-                # Replace percentages when we have no refer_to that
-                # makes sense.
-                result = refer_to
-        else:
-            # Some other values such as 'auto' may be allowed
-            result = value
-            assert allowed_keywords and result in allowed_keywords
+        assert value.unit == '%'
+        result = value.value * refer_to / 100.
     # box attributes are used values
     setattr(box, property_name, result)
 
@@ -56,15 +47,15 @@ def resolve_percentages(box, containing_block):
         maybe_height = cb_height
     else:
         maybe_height = cb_width
-    resolve_one_percentage(box, 'margin_left', cb_width, ['auto'])
-    resolve_one_percentage(box, 'margin_right', cb_width, ['auto'])
-    resolve_one_percentage(box, 'margin_top', maybe_height, ['auto'])
-    resolve_one_percentage(box, 'margin_bottom', maybe_height, ['auto'])
+    resolve_one_percentage(box, 'margin_left', cb_width)
+    resolve_one_percentage(box, 'margin_right', cb_width)
+    resolve_one_percentage(box, 'margin_top', maybe_height)
+    resolve_one_percentage(box, 'margin_bottom', maybe_height)
     resolve_one_percentage(box, 'padding_left', cb_width)
     resolve_one_percentage(box, 'padding_right', cb_width)
     resolve_one_percentage(box, 'padding_top', maybe_height)
     resolve_one_percentage(box, 'padding_bottom', maybe_height)
-    resolve_one_percentage(box, 'width', cb_width, ['auto'])
+    resolve_one_percentage(box, 'width', cb_width)
     # Not supported yet:
 #    resolve_one_percentage(box, 'min_width', cb_width)
 #    resolve_one_percentage(box, 'max_width', cb_width, ['none'])
@@ -74,12 +65,17 @@ def resolve_percentages(box, containing_block):
     if cb_height == 'auto':
         # Special handling when the height of the containing block
         # depends on its content.
-        resolve_one_percentage(box, 'height', 'auto', ['auto'])
+        height = box.style.height
+        if height == 'auto' or height.unit == '%':
+            box.height = 'auto'
+        else:
+            assert height.unit == 'px'
+            box.height = height.value
         # Not supported yet, but min_height is used for margin collapsing.
         resolve_one_percentage(box, 'min_height', 0)
 #        resolve_one_percentage(box, 'max_height', None, ['none'])
     else:
-        resolve_one_percentage(box, 'height', cb_height, ['auto'])
+        resolve_one_percentage(box, 'height', cb_height)
         # Not supported yet, but min_height is used for margin collapsing.
         resolve_one_percentage(box, 'min_height', cb_height)
 #        resolve_one_percentage(box, 'max_height', cb_height, ['none'])

weasyprint/layout/tables.py

@@ -276,7 +276,7 @@ def fixed_table_layout(table):
 
     # `width` on column boxes
     for i, column in enumerate(all_columns):
-        resolve_one_percentage(column, 'width', table.width, ['auto'])
+        resolve_one_percentage(column, 'width', table.width)
         if column.width != 'auto':
             column_widths[i] = column.width