Incorrect aligned dimension extension lines and measurment text for slightly non-vertical segments

[necto]

For certain segments, rendering an aligned dimension results in incorrect extension lines and wrong measurement text. Depending on the point coordinates, it might be correct or wrong, while the dimension.get_measurement() returns the correct value.

Here is the reproducer example:

import ezdxf
print(f"Using ezdxf version: {ezdxf.__version__}")

points = [
    (250235.3373553778, 99368),
    (250235.3373553779, 99412),
]

output_filename = "polyline_example.dxf"

doc = ezdxf.new()
doc.modelspace().add_lwpolyline(points)

p1, p2 = points[0], points[1]
doc.modelspace().add_aligned_dim(p1, p2, distance=20).render()

print(f"Polyline points: {points}")
dim = list(doc.modelspace().query("DIMENSION"))[0]
print(f"Dimension text: {dim.dxf.text}")
print(f"Dimension measurement: {dim.get_measurement()}")
for e in dim.virtual_entities():
    if e.dxftype() == "MTEXT":
        print(f"MTEXT text: {e.dxf.text}")

doc.saveas(output_filename)
print(f"DXF file '{output_filename}' created successfully!")

Note that the distance between the points is ~44 units.

I use python version 3.12.9

Output:

Using ezdxf version: 1.4.2
Polyline points: [(250235.3373553778, 99368), (250235.3373553779, 99412)]
Dimension text: <>
Dimension measurement: 44.0
MTEXT text: 32
DXF file 'polyline_example.dxf' created successfully!

If I change the numeric values ever so slightly, I get the expected parallel lines and correct measurement text:

Using ezdxf version: 1.4.2
Polyline points: [(250235.337355377, 99368), (250235.337355377, 99412)]
Dimension text: <>
Dimension measurement: 44.0
MTEXT text: 44
DXF file 'polyline_example.dxf' created successfully!

[necto]

Here is my workaround:

def avoid_slightly_non_vertical_segments(p1, p2):
    if abs(p1[0] - p2[0]) < 0.001:
        return ((p1[0], p1[1]), (p1[0], p2[1]))
    return (p1, p2)