From 2cbb48e2ef2c20fdf487b9e5b11e02d2da502359 Mon Sep 17 00:00:00 2001
From: Richard Brice <37087370+RickBrice@users.noreply.github.com>
Date: Sun, 13 Sep 2026 11:26:26 -0700
Subject: [PATCH] Improves interactive editing of horizontal alignment

---
 .../bonsai/bim/module/alignment/prop.py       | 19 +++++++++++++++++--
 src/bonsai/bonsai/tool/alignment.py           | 17 +++++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/bonsai/bonsai/bim/module/alignment/prop.py b/src/bonsai/bonsai/bim/module/alignment/prop.py
index 7e6d3d37a1..a3691a9da3 100644
--- a/src/bonsai/bonsai/bim/module/alignment/prop.py
+++ b/src/bonsai/bonsai/bim/module/alignment/prop.py
@@ -39,14 +39,28 @@ def _on_vertical_visibility_update(self, context):
     VerticalProfileDecorator.tag_redraw()
 
 
+# Blender requires a dynamic EnumProperty callback to keep a reference to the
+# items it returns — the strings are read by the C/RNA layer after the Python
+# call returns, and if the list is only local to the function it can be
+# garbage-collected before that happens. Without this cache, the dropdown can
+# resolve its stored index against a stale/freed items list — e.g. right
+# after adding and drawing a new alignment — leaving the dropdown (and the
+# segment table, which reads its value) showing a different alignment than
+# the one actually active in the viewport. See bpy.props.EnumProperty docs.
+_alignment_enum_items_cache: list[tuple[str, str, str]] = []
+
+
 def _alignment_enum_items(self, context):
     """Dynamic items: all top-level IfcAlignment entities in the current file."""
     import bonsai.tool as tool
 
+    global _alignment_enum_items_cache
+
     items = [("0", "— select alignment —", "")]
     ifc_file = tool.Ifc.get()
     if not ifc_file:
-        return items
+        _alignment_enum_items_cache = items
+        return _alignment_enum_items_cache
     try:
         for a in ifc_file.by_type("IfcAlignment"):
             # Skip child alignments (used in multi-vertical template)
@@ -59,7 +73,8 @@ def _alignment_enum_items(self, context):
             items.append((str(a.id()), label, ""))
     except Exception:
         pass
-    return items
+    _alignment_enum_items_cache = items
+    return _alignment_enum_items_cache
 
 
 def _on_active_alignment_update(self, context):
diff --git a/src/bonsai/bonsai/tool/alignment.py b/src/bonsai/bonsai/tool/alignment.py
index 6e8febbc5f..0932e3aa7f 100644
--- a/src/bonsai/bonsai/tool/alignment.py
+++ b/src/bonsai/bonsai/tool/alignment.py
@@ -1057,6 +1057,23 @@ class Alignment:
     @classmethod
     def get_active_alignment(cls) -> ifcopenshell.entity_instance | None:
         if obj := tool.Blender.get_active_object():
+            # PI curve marker empties (see PICurveMarkerProperties) are never
+            # IFC-linked — they're transient viewport helpers — so they need
+            # their own lookup via the alignment_id they were tagged with,
+            # rather than falling through to tool.Ifc.get_entity() below.
+            # Without this, selecting a marker to press Apply Curve leaves
+            # this returning None, and the Alignments tab's dropdown/segment
+            # table (which sync from this) revert to "select an alignment".
+            marker = obj.bonsai_pi_curve_marker
+            if marker.is_pi_marker:
+                ifc_file = tool.Ifc.get()
+                if not ifc_file:
+                    return None
+                try:
+                    alignment = ifc_file.by_id(marker.alignment_id)
+                except RuntimeError:
+                    return None
+                return cls._get_top_level_alignment(alignment) if alignment.is_a("IfcAlignment") else None
             element = tool.Ifc.get_entity(obj)
             if not element:
                 return None