cht: add _BaseAxis.reverse_order getter

Author: scanny

features/cht-axis-props.feature

@@ -164,7 +164,6 @@ Feature: Axis properties
      Then axis.major_gridlines is a MajorGridlines object
 
 
-  @wip
   Scenario Outline: Get Axis.reverse_order
     Given an axis having reverse-order turned <status>
      Then axis.reverse_order is <expected-value>

pptx/chart/axis.py

@@ -10,6 +10,7 @@
     XL_TICK_MARK,
 )
 from pptx.oxml.ns import qn
+from pptx.oxml.simpletypes import ST_Orientation
 from pptx.shared import ElementProxy
 from pptx.text.text import Font, TextFrame
 from pptx.util import lazyproperty
@@ -175,6 +176,21 @@ def minor_tick_mark(self, value):
             return
         self._element._add_minorTickMark(val=value)
 
+    @property
+    def reverse_order(self):
+        """Read/write bool value specifying whether to reverse plotting order for axis.
+
+        For a category axis, this reverses the order in which the categories are
+        displayed. This may be desired, for example, on a (horizontal) bar-chart where
+        by default the first category appears at the bottom. Since we read from
+        top-to-bottom, many viewers may find it most natural for the first category to
+        appear on top.
+
+        For a value axis, it reverses the direction of increasing value from
+        bottom-to-top to top-to-bottom.
+        """
+        return self._element.orientation == ST_Orientation.MAX_MIN
+
     @lazyproperty
     def tick_labels(self):
         """

pptx/oxml/__init__.py

@@ -65,6 +65,7 @@ def register_element_cls(nsptagname, cls):
     CT_Crosses,
     CT_DateAx,
     CT_LblOffset,
+    CT_Orientation,
     CT_Scaling,
     CT_TickLblPos,
     CT_TickMark,
@@ -80,6 +81,7 @@ def register_element_cls(nsptagname, cls):
 register_element_cls("c:majorUnit", CT_AxisUnit)
 register_element_cls("c:minorTickMark", CT_TickMark)
 register_element_cls("c:minorUnit", CT_AxisUnit)
+register_element_cls("c:orientation", CT_Orientation)
 register_element_cls("c:scaling", CT_Scaling)
 register_element_cls("c:tickLblPos", CT_TickLblPos)
 register_element_cls("c:valAx", CT_ValAx)

pptx/oxml/chart/axis.py

@@ -6,7 +6,7 @@
 
 from pptx.enum.chart import XL_AXIS_CROSSES, XL_TICK_LABEL_POSITION, XL_TICK_MARK
 from pptx.oxml.chart.shared import CT_Title
-from pptx.oxml.simpletypes import ST_AxisUnit, ST_LblOffset
+from pptx.oxml.simpletypes import ST_AxisUnit, ST_LblOffset, ST_Orientation
 from pptx.oxml.text import CT_TextBody
 from pptx.oxml.xmlchemy import (
     BaseOxmlElement,
@@ -30,6 +30,18 @@ def defRPr(self):
         defRPr = txPr.defRPr
         return defRPr
 
+    @property
+    def orientation(self):
+        """Value of `val` attribute of `c:scaling/c:orientation` grandchild element.
+
+        Defaults to `ST_Orientation.MIN_MAX` if attribute or any ancestors are not
+        present.
+        """
+        orientation = self.scaling.orientation
+        if orientation is None:
+            return ST_Orientation.MIN_MAX
+        return orientation.val
+
     def _new_title(self):
         return CT_Title.new_title()
 
@@ -155,13 +167,25 @@ class CT_LblOffset(BaseOxmlElement):
     val = OptionalAttribute("val", ST_LblOffset, default=100)
 
 
+class CT_Orientation(BaseOxmlElement):
+    """`c:xAx/c:scaling/c:orientation` element, defining category order.
+
+    Used to reverse the order categories appear in on a bar chart so they start at the
+    top rather than the bottom. Because we read top-to-bottom, the default way looks odd
+    to many and perhaps most folks. Also applicable to value and date axes.
+    """
+
+    val = OptionalAttribute("val", ST_Orientation, default=ST_Orientation.MIN_MAX)
+
+
 class CT_Scaling(BaseOxmlElement):
     """`c:scaling` element.
 
     Defines axis scale characteristics such as maximum value, log vs. linear, etc.
     """
 
     _tag_seq = ("c:logBase", "c:orientation", "c:max", "c:min", "c:extLst")
+    orientation = ZeroOrOne("c:orientation", successors=_tag_seq[2:])
     max = ZeroOrOne("c:max", successors=_tag_seq[3:])
     min = ZeroOrOne("c:min", successors=_tag_seq[4:])
     del _tag_seq

pptx/oxml/simpletypes.py

@@ -1,12 +1,14 @@
 # encoding: utf-8
 
-"""
-Simple type classes, providing validation and format translation for values
-stored in XML element attributes. Naming generally corresponds to the simple
-type in the associated XML schema.
-"""
+"""Simple-type classes.
 
-from __future__ import absolute_import, print_function
+A "simple-type" is a scalar type, generally serving as an XML attribute. This is in
+contrast to a "complex-type" which would specify an XML element.
+
+These objects providing validation and format translation for values stored in XML
+element attributes. Naming generally corresponds to the simple type in the associated
+XML schema.
+"""
 
 import numbers
 
@@ -480,6 +482,15 @@ def validate(cls, value):
         cls.validate_int_in_range(value, 2, 72)
 
 
+class ST_Orientation(XsdStringEnumeration):
+    """Valid values for `val` attribute on c:orientation (CT_Orientation)."""
+
+    MAX_MIN = "maxMin"
+    MIN_MAX = "minMax"
+
+    _members = (MAX_MIN, MIN_MAX)
+
+
 class ST_Overlap(BaseIntType):
     """
     String value is an integer in range -100..100, representing a percent,

tests/chart/test_axis.py

@@ -112,6 +112,10 @@ def it_can_change_its_minor_tick_mark(self, minor_tick_set_fixture):
         axis.minor_tick_mark = new_value
         assert axis._element.xml == expected_xml
 
+    def it_knows_whether_it_renders_in_reverse_order(self, reverse_order_get_fixture):
+        xAx, expected_value = reverse_order_get_fixture
+        assert _BaseAxis(xAx).reverse_order == expected_value
+
     def it_knows_its_tick_label_position(self, tick_lbl_pos_get_fixture):
         axis, expected_value = tick_lbl_pos_get_fixture
         assert axis.tick_label_position == expected_value
@@ -475,6 +479,18 @@ def minor_tick_set_fixture(self, request):
         expected_xml = xml(expected_xAx_cxml)
         return axis, new_value, expected_xml
 
+    @pytest.fixture(
+        params=[
+            ("c:catAx/c:scaling", False),
+            ("c:valAx/c:scaling/c:orientation", False),
+            ("c:catAx/c:scaling/c:orientation{val=minMax}", False),
+            ("c:valAx/c:scaling/c:orientation{val=maxMin}", True),
+        ]
+    )
+    def reverse_order_get_fixture(self, request):
+        xAx_cxml, expected_value = request.param
+        return element(xAx_cxml), expected_value
+
     @pytest.fixture(params=["c:catAx", "c:dateAx", "c:valAx"])
     def tick_labels_fixture(self, request, TickLabels_, tick_labels_):
         xAx_cxml = request.param