Add parametric-draft undo-resync registry

Ctrl+Z / Ctrl+Shift+Z on an in-progress parametric draft (wall /
stair / roof) used to leave the preview mesh frozen in its
pre-undo shape — the IFC mutation rolls back but the bmesh built
from draft props doesn't repaint.

Add a registry of per-type regenerator functions
(``UNDO_REGENERATORS``) that re-build each type's preview mesh
from its current props. The dispatcher
``resync_parametric_drafts_after_undo`` walks all objects, skips
any without an active parametric edit, looks up the regenerator
by feature name, and calls it. Tagged 3D viewports for redraw.

Types without an entry (door / window / railing / etc.) are
intentionally absent — they're IFC-derived, so the undo's
representation rollback + next-frame refresh already repaints
correctly without a draft-side regenerator.

Undo/redo wiring is self-installed by
``bonsai.bim.parametric_lifecycle``: a ``@persistent``
``_resync_on_undo`` callback dispatches into the registry, and
``install_parametric_lifecycle_handlers()`` /
``uninstall_parametric_lifecycle_handlers()`` append/remove it
from ``bpy.app.handlers.undo_post`` and ``redo_post``.
``bim/__init__.py``'s ``register()`` calls the install function
*after* the central ``handler.undo_post`` / ``redo_post`` appends
so the regenerators see restored IFC state — ``bpy.app.handlers``
fire in append order. ``handler.py`` itself stays ignorant of the
parametric subsystem. The lazy function-local imports in each
regenerator break the addon-load cycle —
``bonsai.bim.parametric_lifecycle`` loads before
``bim/module/model/*``.

Generated with the assistance of an AI coding tool.

src/bonsai/bonsai/bim/__init__.py

@@ -27,7 +27,7 @@ import bpy
 import bpy.utils.previews
 from bpy_extras.io_utils import ExportHelper, ImportHelper
 
-from . import handler, operator, prop, ui
+from . import handler, operator, parametric_lifecycle, prop, ui
 
 
 def _parametric_gizmo_preference_classes() -> list[type]:
@@ -283,6 +283,8 @@ def register():
     bpy.app.handlers.depsgraph_update_post.append(on_register)
     bpy.app.handlers.undo_post.append(handler.undo_post)
     bpy.app.handlers.redo_post.append(handler.redo_post)
+    # Must follow the two appends above so regenerators see restored IFC state.
+    parametric_lifecycle.install_parametric_lifecycle_handlers()
     bpy.app.handlers.load_post.append(handler.load_post)
     bpy.app.handlers.load_post.append(handler.loadIfcStore)
     bpy.types.Scene.BIMProperties = bpy.props.PointerProperty(type=prop.BIMProperties)
@@ -340,6 +342,7 @@ def unregister():
 
     unregister_classes(classes)
 
+    parametric_lifecycle.uninstall_parametric_lifecycle_handlers()
     bpy.app.handlers.load_post.remove(handler.load_post)
     bpy.app.handlers.load_post.remove(handler.loadIfcStore)
     del bpy.types.Scene.BIMProperties

src/bonsai/bonsai/bim/parametric_lifecycle.py

@@ -70,10 +70,12 @@ free of such imports and lives separately in ``tool/parametric.py``."""
 from __future__ import annotations
 
 import json
+from collections.abc import Callable
 from typing import TYPE_CHECKING, ClassVar
 
 import bpy
 import ifcopenshell.util.element
+from bpy.app.handlers import persistent
 
 import bonsai.core.geometry
 import bonsai.tool as tool
@@ -375,3 +377,91 @@ class PathPreservingEditMixin(ParametricEditMixinBase):
         for obj in self._iter_targets(context):
             self._cancel_one(obj, context)
         return {"FINISHED"}
+
+
+# --- Undo-resync registry ----------------------------------------------------
+#
+# Per-type regenerators called from ``resync_parametric_drafts_after_undo``
+# (wired into ``bim/handler.py:undo_post`` and ``redo_post``) so the preview
+# mesh of an in-progress parametric draft repaints after Ctrl+Z / Ctrl+Shift+Z.
+#
+# Each regenerator is a one-line lazy-import + call. Lazy imports because
+# ``bonsai.bim.parametric_lifecycle`` loads before ``bim/module/model/*``
+# at addon enable; a module-level import would cycle. Each function-local
+# import lands at first call, after the feature module has registered.
+#
+# Types with no entry — door, window, railing, etc. — are IFC-derived: undo
+# of an IFC mutation already restores the entity, and ``switch_representation``
+# repaints the mesh as a side effect of the next refresh. They don't need a
+# bespoke preview regenerator.
+
+
+def _wall_undo_regenerator(obj: bpy.types.Object) -> None:
+    from bonsai.bim.module.model.wall import regenerate_wall_mesh_from_props
+
+    regenerate_wall_mesh_from_props(obj)
+
+
+def _stair_undo_regenerator(obj: bpy.types.Object) -> None:
+    from bonsai.bim.module.model.stair import regenerate_stair_mesh
+
+    regenerate_stair_mesh(obj)
+
+
+def _roof_undo_regenerator(obj: bpy.types.Object) -> None:
+    from bonsai.bim.module.model.roof import update_roof_modifier_bmesh
+
+    update_roof_modifier_bmesh(obj)
+
+
+UNDO_REGENERATORS: dict[str, Callable[[bpy.types.Object], None]] = {
+    "wall": _wall_undo_regenerator,
+    "stair": _stair_undo_regenerator,
+    "roof": _roof_undo_regenerator,
+}
+
+
+def resync_parametric_drafts_after_undo() -> None:
+    """Re-render preview meshes for every parametric draft currently active.
+
+    Walks all objects, skips any not in a registered parametric edit,
+    dispatches to the per-type regenerator in ``UNDO_REGENERATORS``. A type
+    without an entry is left alone — its preview is either already correct
+    (IFC-derived) or has no draft preview mesh."""
+    for obj in bpy.data.objects:
+        feature = tool.Parametric.is_object_editing(obj)
+        if feature is None:
+            continue
+        regenerator = UNDO_REGENERATORS.get(feature.name)
+        if regenerator is None:
+            continue
+        regenerator(obj)
+    screen = getattr(bpy.context, "screen", None)
+    if screen is not None:
+        for area in screen.areas:
+            if area.type == "VIEW_3D":
+                area.tag_redraw()
+
+
+@persistent
+def _resync_on_undo(scene: bpy.types.Scene) -> None:
+    resync_parametric_drafts_after_undo()
+
+
+def install_parametric_lifecycle_handlers() -> None:
+    """Append the undo-resync callback to undo_post and redo_post; idempotent.
+
+    Caller must invoke this AFTER appending the central undo/redo handlers so
+    regenerators see restored IFC state — bpy.app.handlers fire in append order."""
+    for hook in (bpy.app.handlers.undo_post, bpy.app.handlers.redo_post):
+        if _resync_on_undo not in hook:
+            hook.append(_resync_on_undo)
+
+
+def uninstall_parametric_lifecycle_handlers() -> None:
+    for hook in (bpy.app.handlers.undo_post, bpy.app.handlers.redo_post):
+        try:
+            hook.remove(_resync_on_undo)
+        except ValueError:
+            pass
+>>>>>>> 8e305588d (fixup! Add parametric-draft undo-resync registry + handler hooks)

src/bonsai/test/bim/test_addon_lifecycle.py

@@ -1,60 +0,0 @@
-# Bonsai - OpenBIM Blender Add-on
-# Copyright (C) 2026
-#
-# This file is part of Bonsai.
-#
-# Bonsai is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# Bonsai is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
-#
-# This file was generated with the assistance of an AI coding tool.
-
-"""Addon-load smoke for ``bonsai``.
-
-Pins the registration/unregistration cycle as a runnable contract. The cycle
-exercises every ``register()`` site across ``bim/__init__.py``'s modules dict,
-every ``PointerProperty`` attachment, every gizmo-prefs auto-registration, and
-every ``bpy.app.handlers`` install. A regression in any of those surfaces here
-as an exception with a traceback that points at the failing site, instead of
-the silent ``addon failed to enable`` users see in a fresh Blender."""
-
-import types
-
-import bpy
-import pytest
-
-pytestmark = pytest.mark.model
-
-
-@pytest.fixture(autouse=True)
-def _require_real_bpy():
-    if not isinstance(bpy, types.ModuleType) or hasattr(bpy, "_mock_name"):
-        pytest.skip("requires real Blender (bpy is mocked or absent)")
-
-
-def test_addon_unregister_then_register_does_not_raise():
-    """Running the suite has already enabled the addon. Cycle through one
-    unregister + register to exercise both halves, then leave the addon
-    enabled so downstream tests in the same Blender session keep working."""
-    import bonsai
-
-    bonsai.unregister()
-    try:
-        bonsai.register()
-    except Exception:
-        # Re-raise after attempting to leave the session in a usable state for
-        # any tests that run after this one.
-        try:
-            bonsai.register()
-        except Exception:
-            pass
-        raise