DRY tag-redraw-3D-viewports loops via tool.Blender.update_all_viewports

Five inline copies of the same defensive pattern lived across
``tool/parametric.py``, ``bim/parametric_lifecycle.py``,
``bim/module/model/preview_base.py`` (twice), and as a near-twin
in ``tool/blender.py:update_all_viewports`` itself.

``tool.Blender.update_all_viewports`` already covered the
``tag_redraw`` job but used an ``assert context.screen`` that would
raise during background-mode operators or early-load_post calls
where ``screen`` legitimately is None. Relax to a defensive
``getattr(context, "screen", None)`` + silent return so the helper
fits every caller's needs, then collapse the 4 inline copies to
single calls.

Net -9 LOC. The helper now describes its contract ("silent no-op
when no screen attached") rather than naming specific callers, so
moving a caller doesn't rot the docstring.

Generated with the assistance of an AI coding tool.

src/bonsai/bonsai/bim/module/model/preview_base.py

@@ -126,9 +126,7 @@ def make_dim_setter(
         if props is None:
             return
         setattr(props, field, max(min_value, float(value)))
-        for area in bpy.context.screen.areas if bpy.context.screen else ():
-            if area.type == "VIEW_3D":
-                area.tag_redraw()
+        tool.Blender.update_all_viewports()
 
     return _set
 
@@ -179,10 +177,7 @@ def try_cancel_active_preview(context: bpy.types.Context) -> bool:
             getattr(bpy.ops.bim, op_name)()
             cancelled = True
     if cancelled:
-        screen = context.screen
-        for area in screen.areas if screen else ():
-            if area.type == "VIEW_3D":
-                area.tag_redraw()
+        tool.Blender.update_all_viewports(context)
     return cancelled
 
 

src/bonsai/bonsai/bim/parametric_lifecycle.py

@@ -436,11 +436,7 @@ def resync_parametric_drafts_after_undo() -> None:
         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()
+    tool.Blender.update_all_viewports()
 
 
 @persistent
@@ -464,4 +460,3 @@ def uninstall_parametric_lifecycle_handlers() -> None:
             hook.remove(_resync_on_undo)
         except ValueError:
             pass
->>>>>>> 8e305588d (fixup! Add parametric-draft undo-resync registry + handler hooks)

src/bonsai/bonsai/tool/blender.py

@@ -680,9 +680,13 @@ class Blender(bonsai.core.tool.Blender):
 
     @classmethod
     def update_all_viewports(cls, context: bpy.types.Context | None = None) -> None:
+        """Tag every visible 3D viewport for redraw. Silent no-op when no
+        screen attached (background mode, plug-out, mid-load_post)."""
         context = context or bpy.context
-        assert context.screen
-        for area in context.screen.areas:
+        screen = getattr(context, "screen", None)
+        if screen is None:
+            return
+        for area in screen.areas:
             if area.type == "VIEW_3D":
                 area.tag_redraw()
 

src/bonsai/bonsai/tool/parametric.py

@@ -187,11 +187,7 @@ class Parametric(bonsai.core.tool.Parametric):
 
         cls._geom_generation += 1
         bonsai.bim.handler.update_bim_tool_props()
-        screen = getattr(bpy.context, "screen", None)
-        if screen is not None:
-            for area in screen.areas:
-                if area.type == "VIEW_3D":
-                    area.tag_redraw()
+        tool.Blender.update_all_viewports()
 
     @classmethod
     def find_by_name(cls, name: str) -> Optional[ParametricObject]: