From bde39c12359fe761ef5fe0c128b8029bc8bdd21a Mon Sep 17 00:00:00 2001
From: Petru Conduraru <petru@bimvoice.com>
Date: Thu, 16 Jul 2026 16:52:36 +0300
Subject: [PATCH] Bonsai: fix BCF viewpoint line markup crash on modern Grease
 Pencil API

draw_lines() used the pre-4.3 Annotation Grease Pencil scripting API
(frame.strokes.new()), which Blender removed the stroke-mutation
methods from in 4.3 and dropped scene.grease_pencil/the legacy
datablock entirely in 5.1. Activating a BCF viewpoint whose markup
includes lines then crashed with
AttributeError: bpy_prop_collection: attribute "new" not found.

Detect the available API by capability (frame.drawing presence) rather
than a hardcoded version check, since Blender exposes the rewritten,
object-based Grease Pencil through grease_pencils_v3 on 4.3-5.0 and
through the unified grease_pencils on 5.1+, while 4.2 still has the
original Annotation API. Reproduced live against the reporter's actual
BCF/IFC files on Blender 4.5.8 and 5.1.2: the crash occurs on
unpatched code, and no crash occurs after the fix, with the viewpoint
markup lines correctly drawn on both.

Fixes #7318.

Generated with the assistance of an AI coding tool.
---
 src/bonsai/bonsai/bim/module/bcf/operator.py | 68 ++++++++++++++------
 1 file changed, 50 insertions(+), 18 deletions(-)

diff --git a/src/bonsai/bonsai/bim/module/bcf/operator.py b/src/bonsai/bonsai/bim/module/bcf/operator.py
index 461321852d..f3d1c202fc 100644
--- a/src/bonsai/bonsai/bim/module/bcf/operator.py
+++ b/src/bonsai/bonsai/bim/module/bcf/operator.py
@@ -1259,9 +1259,7 @@ class ActivateBcfViewpoint(bpy.types.Operator):
         if self.file:
             self.set_viewpoint_components(viewpoint, context)
 
-        gp = bpy.data.grease_pencils.get("BCF")
-        if gp:
-            bpy.data.grease_pencils.remove(gp)
+        self.delete_lines()
         if viewpoint.visualization_info.lines:
             self.draw_lines(viewpoint, context)
 
@@ -1434,24 +1432,58 @@ class ActivateBcfViewpoint(bpy.types.Operator):
             if obj:
                 obj.color = self.hex_to_rgb(color)
 
+    def delete_lines(self) -> None:
+        if obj := bpy.data.objects.get("BCF"):
+            bpy.data.objects.remove(obj)
+        for grease_pencils in (bpy.data.grease_pencils, getattr(bpy.data, "grease_pencils_v3", None)):
+            if grease_pencils is not None and (gp := grease_pencils.get("BCF")):
+                grease_pencils.remove(gp)
+
     def draw_lines(self, viewpoint: bcf.agnostic.visinfo.VisualizationInfoHandler, context: bpy.types.Context) -> None:
-        gp = bpy.data.grease_pencils.new("BCF")
-        scene = context.scene
-        scene.grease_pencil = gp
-        scene.frame_set(1)
+        # Blender 4.3+ moved the object-based Grease Pencil to its own
+        # `grease_pencils_v3` collection (merged back into `grease_pencils`
+        # in 5.1+, which also dropped the legacy Annotation API used below).
+        grease_pencils = getattr(bpy.data, "grease_pencils_v3", None)
+        if grease_pencils is None:
+            grease_pencils = bpy.data.grease_pencils
+        gp = grease_pencils.new("BCF")
         layer = gp.layers.new("BCF Annotation", set_active=True)
-        layer.thickness = 3
-        layer.color = (1, 0, 0)
         frame = layer.frames.new(1)
-        stroke = frame.strokes.new()
-        stroke.display_mode = "3DSPACE"
-        stroke.points.add(len(viewpoint.visualization_info.lines.line) * 2)
-        coords = []
-        for l in viewpoint.visualization_info.lines.line:
-            coords.extend(
-                [l.start_point.x, l.start_point.y, l.start_point.z, l.end_point.x, l.end_point.y, l.end_point.z]
-            )
-        stroke.points.foreach_set("co", coords)
+        lines = viewpoint.visualization_info.lines.line
+        if (drawing := getattr(frame, "drawing", None)) is not None:
+            obj = bpy.data.objects.new("BCF", gp)
+            context.scene.collection.objects.link(obj)
+            drawing.add_strokes(sizes=[2] * len(lines))
+            coords = []
+            for l in lines:
+                coords.extend(
+                    [l.start_point.x, l.start_point.y, l.start_point.z, l.end_point.x, l.end_point.y, l.end_point.z]
+                )
+            drawing.attributes["position"].data.foreach_set("vector", coords)
+            radius = drawing.attributes.new("radius", "FLOAT", "POINT")
+            radius.data.foreach_set("value", [0.01] * (len(lines) * 2))
+            drawing.tag_positions_changed()
+            mat = bpy.data.materials.get("BCF Annotation")
+            if mat is None:
+                mat = bpy.data.materials.new("BCF Annotation")
+                bpy.data.materials.create_gpencil_data(mat)
+            mat.grease_pencil.color = (1, 0, 0, 1)
+            gp.materials.append(mat)
+        else:
+            scene = context.scene
+            scene.grease_pencil = gp
+            scene.frame_set(1)
+            layer.thickness = 3
+            layer.color = (1, 0, 0)
+            stroke = frame.strokes.new()
+            stroke.display_mode = "3DSPACE"
+            stroke.points.add(len(lines) * 2)
+            coords = []
+            for l in lines:
+                coords.extend(
+                    [l.start_point.x, l.start_point.y, l.start_point.z, l.end_point.x, l.end_point.y, l.end_point.z]
+                )
+            stroke.points.foreach_set("co", coords)
 
     def create_clipping_planes(self, viewpoint: bcf.agnostic.visinfo.VisualizationInfoHandler) -> None:
         n = 0