Fixes problems with referents

src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_layout.py

@@ -89,7 +89,8 @@ def _add_segment_to_layout(file: ifcopenshell.file, layout: entity_instance, seg
         # update the zero length layout segment
         unit_scale = ifcopenshell.util.unit.calculate_unit_scale(file)
 
-        zero_length_segment = layout.IsNestedBy[0].RelatedObjects[-1]
+        segment_nest = ifcopenshell.api.alignment.get_alignment_segment_nest(layout)
+        zero_length_segment = segment_nest.RelatedObjects[-1]
         # DesignParameters.StartPoint for IfcAlignmentHorizontalSegment is automatically updated when the
         # geometric representation is updated because the semantic and geometric data use the same IfcPoint.
         # This is not the case of IfcAlignmentVerticalSegment and IfcAlignmentCantSegment. For these
@@ -136,7 +137,8 @@ def _add_segment_to_layout(file: ifcopenshell.file, layout: entity_instance, seg
             start_dist_along = segment.DesignParameters.StartDistAlong + segment.DesignParameters.HorizontalLength
             zero_length_segment.DesignParameters.StartDistAlong = start_dist_along
 
-        end_referent = zero_length_segment.IsNestedBy[0].RelatedObjects[0]
+        referent_nest = ifcopenshell.api.alignment.get_referent_nest(file,layout)
+        end_referent = referent_nest.RelatedObjects[-1]
         end_referent.Name = f"{_get_segment_start_point_label(zero_length_segment,None)} ({ifcopenshell.util.alignment.station_as_string(file,start_station+start_dist_along)})"
 
         # update the referent's geometric representation's location
@@ -173,12 +175,12 @@ def _add_segment_to_layout(file: ifcopenshell.file, layout: entity_instance, seg
 
         # get the previous segment. Working from the end of the basis curve, -1 is zero length segment
         # -2 is the newly added segment, so -3 is the segment occuring just before the newly added segment
-        segment_nest = ifcopenshell.api.alignment.get_alignment_segment_nest(layout)
         prev_segment = segment_nest.RelatedObjects[-3] if 2 < len(segment_nest.RelatedObjects) else None
         name = f"{_get_segment_start_point_label(prev_segment,segment)} ({ifcopenshell.util.alignment.station_as_string(file,station)})"
         referent = ifcopenshell.api.alignment.add_stationing_referent(
-            file, segment, distance_along=dist_along, station=station, name=name
+            file, layout, distance_along=dist_along, station=station, name=name, positioned_product=segment
         )
+        ifcopenshell.api.nest.reorder_nesting(file,referent,-1,-1)
 
         if len(curve.Segments) == 2 and layout.is_a("IfcAlignmentHorizontal"):
             # this is the first real segment in the horizontal alignment

src/ifcopenshell-python/ifcopenshell/api/alignment/_add_zero_length_segment.py

@@ -48,8 +48,9 @@ def _add_zero_length_segment(file: ifcopenshell.file, layout: entity_instance) -
     if curve:
         ifcopenshell.api.alignment.add_zero_length_segment(file, curve)
 
-        segment = layout.IsNestedBy[0].RelatedObjects[-1]
+        segment_nest = ifcopenshell.api.alignment.get_alignment_segment_nest(layout)
+        segment = segment_nest.RelatedObjects[-1]
         alignment = ifcopenshell.api.alignment.get_alignment(layout)
         station = ifcopenshell.api.alignment.get_alignment_station(file, alignment)
         name = f"{_get_segment_start_point_label(segment,None)} ({ifcopenshell.util.alignment.station_as_string(file,station)})"
-        ifcopenshell.api.alignment.add_stationing_referent(file, segment, 0.0, station, name=name)
+        ifcopenshell.api.alignment.add_stationing_referent(file, layout, 0.0, station, name, segment)

src/ifcopenshell-python/ifcopenshell/api/alignment/add_stationing_referent.py

@@ -34,6 +34,7 @@ def add_stationing_referent(
     distance_along: float,
     station: float,
     name: str,
+    positioned_product: entity_instance
 ) -> entity_instance:
     """
     Adds an IfcReferent to the element with the Pset_Stationing property set.
@@ -43,6 +44,7 @@ def add_stationing_referent(
     :param distance_along: distance along the alignment curve
     :param station: station value
     :param name: name to assign to IfcReferent.Name, typically a stringized version of the station value
+    :param positioned_product: the product whose position is informed by the referent 
     :return: referent
 
     Example:
@@ -54,9 +56,17 @@ def add_stationing_referent(
     """
     alignment = element
 
+    layout_types = [
+        "IfcAlignmentHorizontal",
+        "IfcAlignmentVertical",
+        "IfcAlignmentCant",
+    ]
+
     if element.is_a("IfcAlignmentSegment"):
         layout = element.Nests[0].RelatingObject
         alignment = ifcopenshell.api.alignment.get_alignment(layout)
+    elif element.is_a() in layout_types:
+        alignment = ifcopenshell.api.alignment.get_alignment(element)
 
     basis_curve = ifcopenshell.api.alignment.get_basis_curve(alignment)
 
@@ -137,15 +147,15 @@ def add_stationing_referent(
     nest = ifcopenshell.api.alignment.get_referent_nest(file,element)
     nest.RelatedObjects += (referent,)
 
-    if len(alignment.Positions) == 0:
+    if len(referent.Positions) == 0:
         rel_positions = file.createIfcRelPositions(
             GlobalId=ifcopenshell.guid.new(),
-            RelatingPositioningElement=alignment,
+            RelatingPositioningElement=referent,
             RelatedProducts=[
-                referent,
+                positioned_product,
             ],
         )
     else:
-        alignment.Positions[0].RelatedProducts += (referent,)
+        referent.Positions[0].RelatedProducts += (positioned_product,)
 
     return referent

src/ifcopenshell-python/ifcopenshell/api/alignment/create.py

@@ -86,7 +86,7 @@ def create(
     if include_geometry:
         # define stationing
         name = ifcopenshell.util.alignment.station_as_string(file, start_station)
-        referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, start_station, name)
+        referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, start_station, name, alignment)
 
 
     # IFC 4.1.4.1.1 Alignment Aggregation To Project

src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_polyline.py

@@ -137,13 +137,11 @@ def create_as_polyline(
         Name=name,
     )
 
-    # _create_layout(file,alignment,points)
-
     _create_polyline_representation(file, alignment, points)
 
     # define stationing
     name = ifcopenshell.util.alignment.station_as_string(file, start_station)
-    referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, start_station, name)
+    referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, start_station, name, alignment)
     ifcopenshell.api.nest.reorder_nesting(file, referent, -1, 0)
 
     # IFC 4.1.4.1.1 Alignment Aggregation To Project

src/ifcopenshell-python/ifcopenshell/api/alignment/util.py

@@ -162,3 +162,11 @@ def print_composite_curve_deep(curve):
         print(" " * 4, segment.Placement)
         print(" " * 4, segment.Placement.Location)
         print(" " * 4, segment.Placement.RefDirection)
+
+def print_positioned_products(file: ifcopenshell.file):
+    referents = file.by_type("IfcReferent")
+    for referent in referents:
+        print(referent)
+        for rel in referent.Positions:
+            for product in rel.RelatedProducts:
+                print(" " * 2,product)