ColumnWidths: add support for fractions

Also: add 'HALVES' (/2), similar to 'QUARTERS' (/4)

CHANGES.rst

@@ -20,6 +20,7 @@ Fixed:
 * When a caption occurs in an unnumbered chapter, an exception aborts rendering
   (even when ``number_separator`` style attribute is set to ``None``)
 * Handling of base template specified as string in a template configuration
+* Table column widths entries now also accept fractions
 
 
 Release 0.5.0 (2021-02-03)
@@ -33,7 +34,7 @@ New Features:
   style property.
 * Table: in addition to fixed and relative-width columns, you can indicate
   columns to be automatically sized by specifying a value of 'auto' in the
-  'column_widths' style parameter in yout style sheet.
+  'column_widths' style parameter in your style sheet.
 * docutils frontend: support the ``:align:`` option to table directives, which
   will override the alignment set for the table in the style sheet.
 * The starting number of enumerated lists in reStructuredText is respected.

src/rinoh/dimension.py

@@ -353,4 +353,5 @@ def __rmul__(self, nominator):
 
 
 PERCENT = FractionUnit(100, '%')            #: fraction of 100
+HALVES = FractionUnit(2, '/2')              #: fraction of 2
 QUARTERS = FractionUnit(4, '/4')            #: fraction of 4

src/rinoh/table.py

@@ -73,7 +73,7 @@ class ColumnWidths(AcceptNoneAttributeType):
     def check_type(cls, value):
         return (super().check_type(value)
                 or (isinstance(value, list)
-                    and all(item is None or isinstance(item, (Dimension, int))
+                    and all(item is None or isinstance(item, (DimBase, int))
                             for item in value)))
 
     @classmethod

tests/test_parse.py

@@ -11,7 +11,7 @@
 from rinoh.attribute import OptionSet, Bool, Integer, ParseError
 from rinoh.color import Color, HexColor
 from rinoh.dimension import (Dimension, PT, PICA, INCH, MM, CM,
-                             PERCENT, QUARTERS)
+                             PERCENT, HALVES, QUARTERS)
 from rinoh.draw import Stroke
 from rinoh.flowable import FlowableWidth, HorizontalAlignment, Break
 from rinoh.font.style import ClassSet, FontWeight, FontSlant, FontWidth
@@ -261,6 +261,8 @@ def test_dimension_from_string():
     assert Dimension.from_string('-2.1 cm') == -2.1*CM
     assert Dimension.from_string('21%') == 21*PERCENT
     assert Dimension.from_string('-16.12%') == -16.12*PERCENT
+    assert Dimension.from_string('1/2') == 1*HALVES
+    assert Dimension.from_string('3/2') == 3*HALVES
     assert Dimension.from_string('3/4') == 3*QUARTERS
     with pytest.raises(ParseError):
         assert Dimension.from_string('20inch')
@@ -456,6 +458,10 @@ def test_column_widths_from_string():
     assert ColumnWidths.from_string('2      4  6') == [2, 4, 6]
     assert ColumnWidths.from_string('6  5   4   ') == [6, 5, 4]
     assert ColumnWidths.from_string('1pt 2cm 3in') == [1*PT, 2*CM, 3*INCH]
+    assert ColumnWidths.from_string('20% 30%') == [20*PERCENT, 30*PERCENT]
+    assert ColumnWidths.from_string('1/2 3/4') == [1*HALVES, 3*QUARTERS]
+    assert ColumnWidths.from_string('1/2 auto 20%') == [1*HALVES, None,
+                                                        20*PERCENT]
     assert ColumnWidths.from_string('4 pt 5 cm 6 in') == [4*PT, 5*CM, 6*INCH]
     assert ColumnWidths.from_string('7pt 8 cm 9in') == [7*PT, 8*CM, 9*INCH]
     assert ColumnWidths.from_string('10 20 1cm 30') == [10, 20, 1*CM, 30]