feature: add arrowhead style, width, and length properties to LineFormat

Add begin/end arrowhead properties to LineFormat for controlling arrow
styles on lines and connectors. Introduces MSO_LINE_END_TYPE and
MSO_LINE_END_SIZE enums and models CT_LineEndProperties for the
a:headEnd and a:tailEnd XML elements.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: MHoroszowski

features/dml-line.feature

@@ -33,6 +33,30 @@ Feature: Get and change line properties
       | solid       | None              |
 
 
+  Scenario Outline: LineFormat.end_arrowhead_style getter
+    Given a LineFormat object as line having <arrowhead> end arrowhead
+     Then line.end_arrowhead_style is <value>
+
+    Examples: End arrowhead styles
+      | arrowhead   | value                         |
+      | no explicit | None                          |
+      | triangle    | MSO_LINE_END_TYPE.TRIANGLE    |
+
+  Scenario: LineFormat.end_arrowhead_style setter
+    Given a LineFormat object as line having no explicit end arrowhead
+     When I assign MSO_LINE_END_TYPE.STEALTH to line.end_arrowhead_style
+     Then line.end_arrowhead_style is MSO_LINE_END_TYPE.STEALTH
+
+  Scenario Outline: LineFormat.begin_arrowhead_style getter
+    Given a LineFormat object as line having <arrowhead> begin arrowhead
+     Then line.begin_arrowhead_style is <value>
+
+    Examples: Begin arrowhead styles
+      | arrowhead   | value                         |
+      | no explicit | None                          |
+      | stealth     | MSO_LINE_END_TYPE.STEALTH     |
+
+
   Scenario: LineFormat.fill
     Given a LineFormat object as line
      Then line.fill is a FillFormat object

features/steps/line.py

@@ -6,7 +6,7 @@
 from helpers import test_pptx
 
 from pptx import Presentation
-from pptx.enum.dml import MSO_LINE
+from pptx.enum.dml import MSO_LINE, MSO_LINE_END_TYPE
 from pptx.util import Length, Pt
 
 # given ===================================================
@@ -25,6 +25,20 @@ def given_a_LineFormat_object_as_line_having_dash_style(context, current):
     context.line = shape.line
 
 
+@given("a LineFormat object as line having {arrowhead} end arrowhead")
+def given_a_LineFormat_object_as_line_having_end_arrowhead(context, arrowhead):
+    shape_idx = {"no explicit": 0, "triangle": 1}[arrowhead]
+    shape = Presentation(test_pptx("dml-line-end")).slides[0].shapes[shape_idx]
+    context.line = shape.line
+
+
+@given("a LineFormat object as line having {arrowhead} begin arrowhead")
+def given_a_LineFormat_object_as_line_having_begin_arrowhead(context, arrowhead):
+    shape_idx = {"no explicit": 0, "stealth": 2}[arrowhead]
+    shape = Presentation(test_pptx("dml-line-end")).slides[0].shapes[shape_idx]
+    context.line = shape.line
+
+
 @given("a LineFormat object as line having {line_width} width")
 def given_a_LineFormat_object_as_line_having_width(context, line_width):
     shape_idx = {"no explicit": 0, "1 pt": 1}[line_width]
@@ -47,6 +61,16 @@ def when_I_assign_value_to_line_dash_style(context, value_key):
     context.line.dash_style = value
 
 
+@when("I assign {value_key} to line.end_arrowhead_style")
+def when_I_assign_value_to_line_end_arrowhead_style(context, value_key):
+    value = {
+        "None": None,
+        "MSO_LINE_END_TYPE.TRIANGLE": MSO_LINE_END_TYPE.TRIANGLE,
+        "MSO_LINE_END_TYPE.STEALTH": MSO_LINE_END_TYPE.STEALTH,
+    }[value_key]
+    context.line.end_arrowhead_style = value
+
+
 @when("I assign {line_width} to line.width")
 def when_I_assign_value_to_line_width(context, line_width):
     value = {"None": None, "1 pt": Pt(1), "2.34 pt": Pt(2.34)}[line_width]
@@ -81,6 +105,27 @@ def then_line_dash_style_is_value(context, dash_style):
     )
 
 
+@then("line.end_arrowhead_style is {value_key}")
+def then_line_end_arrowhead_style_is_value(context, value_key):
+    expected_value = {
+        "None": None,
+        "MSO_LINE_END_TYPE.TRIANGLE": MSO_LINE_END_TYPE.TRIANGLE,
+        "MSO_LINE_END_TYPE.STEALTH": MSO_LINE_END_TYPE.STEALTH,
+    }[value_key]
+    actual_value = context.line.end_arrowhead_style
+    assert actual_value == expected_value, "expected %s, got %s" % (expected_value, actual_value)
+
+
+@then("line.begin_arrowhead_style is {value_key}")
+def then_line_begin_arrowhead_style_is_value(context, value_key):
+    expected_value = {
+        "None": None,
+        "MSO_LINE_END_TYPE.STEALTH": MSO_LINE_END_TYPE.STEALTH,
+    }[value_key]
+    actual_value = context.line.begin_arrowhead_style
+    assert actual_value == expected_value, "expected %s, got %s" % (expected_value, actual_value)
+
+
 @then("line.fill is a FillFormat object")
 def then_line_fill_is_a_FillFormat_object(context):
     class_name = context.line.fill.__class__.__name__

features/steps/test_files/dml-line-end.pptx

@@ -2,10 +2,15 @@
 
 from __future__ import annotations
 
+from typing import TYPE_CHECKING
+
 from pptx.dml.fill import FillFormat
-from pptx.enum.dml import MSO_FILL
+from pptx.enum.dml import MSO_FILL, MSO_LINE_END_SIZE, MSO_LINE_END_TYPE
 from pptx.util import Emu, lazyproperty
 
+if TYPE_CHECKING:
+    from pptx.oxml.shapes.shared import CT_LineEndProperties
+
 
 class LineFormat(object):
     """Provides access to line properties such as color, style, and width.
@@ -18,6 +23,69 @@ def __init__(self, parent):
         super(LineFormat, self).__init__()
         self._parent = parent
 
+    @property
+    def begin_arrowhead_length(self) -> MSO_LINE_END_SIZE | None:
+        """Size of the arrowhead at the beginning of the line.
+
+        Read/write. Returns a member of :ref:`MsoArrowheadSize` or |None| if no explicit value
+        has been set. Assigning |None| removes any existing value.
+        """
+        headEnd = self._headEnd
+        if headEnd is None:
+            return None
+        return headEnd.len
+
+    @begin_arrowhead_length.setter
+    def begin_arrowhead_length(self, value: MSO_LINE_END_SIZE | None) -> None:
+        if value is None:
+            headEnd = self._headEnd
+            if headEnd is not None:
+                del headEnd.attrib["len"]
+            return
+        self._get_or_add_headEnd().len = value
+
+    @property
+    def begin_arrowhead_style(self) -> MSO_LINE_END_TYPE | None:
+        """Type of arrowhead at the beginning of the line.
+
+        Read/write. Returns a member of :ref:`MsoArrowheadStyle` or |None| if no explicit value
+        has been set. Assigning |None| removes any existing value.
+        """
+        headEnd = self._headEnd
+        if headEnd is None:
+            return None
+        return headEnd.type
+
+    @begin_arrowhead_style.setter
+    def begin_arrowhead_style(self, value: MSO_LINE_END_TYPE | None) -> None:
+        if value is None:
+            headEnd = self._headEnd
+            if headEnd is not None:
+                del headEnd.attrib["type"]
+            return
+        self._get_or_add_headEnd().type = value
+
+    @property
+    def begin_arrowhead_width(self) -> MSO_LINE_END_SIZE | None:
+        """Width of the arrowhead at the beginning of the line.
+
+        Read/write. Returns a member of :ref:`MsoArrowheadSize` or |None| if no explicit value
+        has been set. Assigning |None| removes any existing value.
+        """
+        headEnd = self._headEnd
+        if headEnd is None:
+            return None
+        return headEnd.w
+
+    @begin_arrowhead_width.setter
+    def begin_arrowhead_width(self, value: MSO_LINE_END_SIZE | None) -> None:
+        if value is None:
+            headEnd = self._headEnd
+            if headEnd is not None:
+                del headEnd.attrib["w"]
+            return
+        self._get_or_add_headEnd().w = value
+
     @lazyproperty
     def color(self):
         """
@@ -32,6 +100,69 @@ def color(self):
             self.fill.solid()
         return self.fill.fore_color
 
+    @property
+    def end_arrowhead_length(self) -> MSO_LINE_END_SIZE | None:
+        """Size of the arrowhead at the end of the line.
+
+        Read/write. Returns a member of :ref:`MsoArrowheadSize` or |None| if no explicit value
+        has been set. Assigning |None| removes any existing value.
+        """
+        tailEnd = self._tailEnd
+        if tailEnd is None:
+            return None
+        return tailEnd.len
+
+    @end_arrowhead_length.setter
+    def end_arrowhead_length(self, value: MSO_LINE_END_SIZE | None) -> None:
+        if value is None:
+            tailEnd = self._tailEnd
+            if tailEnd is not None:
+                del tailEnd.attrib["len"]
+            return
+        self._get_or_add_tailEnd().len = value
+
+    @property
+    def end_arrowhead_style(self) -> MSO_LINE_END_TYPE | None:
+        """Type of arrowhead at the end of the line.
+
+        Read/write. Returns a member of :ref:`MsoArrowheadStyle` or |None| if no explicit value
+        has been set. Assigning |None| removes any existing value.
+        """
+        tailEnd = self._tailEnd
+        if tailEnd is None:
+            return None
+        return tailEnd.type
+
+    @end_arrowhead_style.setter
+    def end_arrowhead_style(self, value: MSO_LINE_END_TYPE | None) -> None:
+        if value is None:
+            tailEnd = self._tailEnd
+            if tailEnd is not None:
+                del tailEnd.attrib["type"]
+            return
+        self._get_or_add_tailEnd().type = value
+
+    @property
+    def end_arrowhead_width(self) -> MSO_LINE_END_SIZE | None:
+        """Width of the arrowhead at the end of the line.
+
+        Read/write. Returns a member of :ref:`MsoArrowheadSize` or |None| if no explicit value
+        has been set. Assigning |None| removes any existing value.
+        """
+        tailEnd = self._tailEnd
+        if tailEnd is None:
+            return None
+        return tailEnd.w
+
+    @end_arrowhead_width.setter
+    def end_arrowhead_width(self, value: MSO_LINE_END_SIZE | None) -> None:
+        if value is None:
+            tailEnd = self._tailEnd
+            if tailEnd is not None:
+                del tailEnd.attrib["w"]
+            return
+        self._get_or_add_tailEnd().w = value
+
     @property
     def dash_style(self):
         """Return value indicating line style.
@@ -88,13 +219,37 @@ def width(self, emu):
         ln = self._get_or_add_ln()
         ln.w = emu
 
+    def _get_or_add_headEnd(self) -> CT_LineEndProperties:
+        """Return the `a:headEnd` element, creating it if not present."""
+        return self._get_or_add_ln().get_or_add_headEnd()
+
     def _get_or_add_ln(self):
         """
         Return the ``<a:ln>`` element containing the line format properties
         in the XML.
         """
         return self._parent.get_or_add_ln()
 
+    def _get_or_add_tailEnd(self) -> CT_LineEndProperties:
+        """Return the `a:tailEnd` element, creating it if not present."""
+        return self._get_or_add_ln().get_or_add_tailEnd()
+
+    @property
+    def _headEnd(self) -> CT_LineEndProperties | None:
+        """Return `a:headEnd` element or None if not present."""
+        ln = self._ln
+        if ln is None:
+            return None
+        return ln.headEnd
+
     @property
     def _ln(self):
         return self._parent.ln
+
+    @property
+    def _tailEnd(self) -> CT_LineEndProperties | None:
+        """Return `a:tailEnd` element or None if not present."""
+        ln = self._ln
+        if ln is None:
+            return None
+        return ln.tailEnd

src/pptx/dml/line.py

@@ -139,6 +139,63 @@ class MSO_LINE_DASH_STYLE(BaseXmlEnum):
 MSO_LINE = MSO_LINE_DASH_STYLE
 
 
+class MSO_LINE_END_TYPE(BaseXmlEnum):
+    """Specifies the style of arrowhead at the end of a line.
+
+    Example::
+
+        from pptx.enum.dml import MSO_LINE_END_TYPE
+
+        shape.line.end_arrowhead_style = MSO_LINE_END_TYPE.TRIANGLE
+
+    MS API name: `MsoArrowheadStyle`
+
+    https://learn.microsoft.com/en-us/office/vba/api/Office.MsoArrowheadStyle
+    """
+
+    NONE = (1, "none", "No arrowhead.")
+    """No arrowhead."""
+
+    TRIANGLE = (2, "triangle", "A triangular arrowhead.")
+    """A triangular arrowhead."""
+
+    STEALTH = (3, "stealth", "A stealth-shaped arrowhead.")
+    """A stealth-shaped arrowhead."""
+
+    DIAMOND = (4, "diamond", "A diamond-shaped arrowhead.")
+    """A diamond-shaped arrowhead."""
+
+    OVAL = (5, "oval", "An oval arrowhead.")
+    """An oval arrowhead."""
+
+    OPEN = (6, "arrow", "An open arrowhead.")
+    """An open arrowhead."""
+
+
+class MSO_LINE_END_SIZE(BaseXmlEnum):
+    """Specifies the width or length of an arrowhead at the end of a line.
+
+    Example::
+
+        from pptx.enum.dml import MSO_LINE_END_SIZE
+
+        shape.line.end_arrowhead_width = MSO_LINE_END_SIZE.MEDIUM
+
+    MS API name: `MsoArrowheadWidth` / `MsoArrowheadLength`
+
+    https://learn.microsoft.com/en-us/office/vba/api/Office.MsoArrowheadWidth
+    """
+
+    SMALL = (1, "sm", "A small arrowhead.")
+    """A small arrowhead."""
+
+    MEDIUM = (2, "med", "A medium arrowhead.")
+    """A medium arrowhead."""
+
+    LARGE = (3, "lg", "A large arrowhead.")
+    """A large arrowhead."""
+
+
 class MSO_PATTERN_TYPE(BaseXmlEnum):
     """Specifies the fill pattern used in a shape.
 

src/pptx/enum/dml.py

@@ -370,6 +370,7 @@ def register_element_cls(nsptagname: str, cls: Type[BaseOxmlElement]):
 
 from pptx.oxml.shapes.shared import (  # noqa: E402
     CT_ApplicationNonVisualDrawingProps,
+    CT_LineEndProperties,
     CT_LineProperties,
     CT_NonVisualDrawingProps,
     CT_Placeholder,
@@ -382,8 +383,10 @@ def register_element_cls(nsptagname: str, cls: Type[BaseOxmlElement]):
 register_element_cls("a:chExt", CT_PositiveSize2D)
 register_element_cls("a:chOff", CT_Point2D)
 register_element_cls("a:ext", CT_PositiveSize2D)
+register_element_cls("a:headEnd", CT_LineEndProperties)
 register_element_cls("a:ln", CT_LineProperties)
 register_element_cls("a:off", CT_Point2D)
+register_element_cls("a:tailEnd", CT_LineEndProperties)
 register_element_cls("a:xfrm", CT_Transform2D)
 register_element_cls("c:spPr", CT_ShapeProperties)
 register_element_cls("p:cNvPr", CT_NonVisualDrawingProps)