Handle fractional twips measures

src/docx/oxml/simpletypes.py

@@ -399,7 +399,10 @@ class ST_TwipsMeasure(XsdUnsignedLong):
     def convert_from_xml(cls, str_value: str) -> Length:
         if "i" in str_value or "m" in str_value or "p" in str_value:
             return ST_UniversalMeasure.convert_from_xml(str_value)
-        return Twips(int(str_value))
+        try:
+            return Twips(int(str_value))
+        except ValueError:
+            return Twips(int(round(float(str_value))))
 
     @classmethod
     def convert_to_xml(cls, value: int | Length) -> str:

tests/oxml/test_simpletypes.py

@@ -0,0 +1,38 @@
+"""Unit test suite for the docx.oxml.simpletypes module."""
+
+import pytest
+
+from docx.oxml.simpletypes import ST_TwipsMeasure
+from docx.shared import Inches, Twips
+
+
+class DescribeST_TwipsMeasure:
+    @pytest.mark.parametrize(
+        ("str_value", "expected_twips"),
+        [("0.49", 0), ("0.51", 1), ("1.49", 1), ("1.51", 2)],
+    )
+    def it_accepts_fractional_twips(self, str_value: str, expected_twips: int):
+        value = ST_TwipsMeasure.convert_from_xml(str_value)
+
+        assert value == Twips(expected_twips)
+
+    @pytest.mark.parametrize("str_value", ["120", "9007199254740993"])
+    def it_preserves_exact_integer_twips(self, str_value: str):
+        value = ST_TwipsMeasure.convert_from_xml(str_value)
+
+        assert value == Twips(int(str_value))
+
+    def it_preserves_unit_suffixed_measurements(self):
+        value = ST_TwipsMeasure.convert_from_xml("1in")
+
+        assert value == Inches(1)
+
+    @pytest.mark.parametrize("str_value", ["not-a-number", "NaN", "Infinity", "-Infinity"])
+    def it_rejects_invalid_or_non_finite_measurements(self, str_value: str):
+        with pytest.raises((ValueError, OverflowError)):
+            ST_TwipsMeasure.convert_from_xml(str_value)
+
+    def it_serializes_measurements_as_integer_twips(self):
+        str_value = ST_TwipsMeasure.convert_to_xml(Twips(42))
+
+        assert str_value == "42"

tests/test_section.py

@@ -470,6 +470,14 @@ def it_knows_its_page_margins(
 
         assert value == expected_value
 
+    def it_accepts_a_fractional_right_margin(self, document_part_: Mock):
+        sectPr = cast(CT_SectPr, element("w:sectPr/w:pgMar{w:right=0.218505859375}"))
+        section = Section(sectPr, document_part_)
+
+        right_margin = section.right_margin
+
+        assert right_margin == 0
+
     @pytest.mark.parametrize(
         ("sectPr_cxml", "margin_prop_name", "value", "expected_cxml"),
         [