Fixed bug with remembering materials assigned to faces

The problem was that bim.update_representation was assigning representation styles without taking into account that some styles may not be actually used in the mesh, so it was always assigning first style (blender material) to the first IFCPOLYGONALFACESET even though it might be using for example the 3rd style.

More - https://community.osarch.org/discussion/1636/materials-not-remembering-their-assigment

src/blenderbim/blenderbim/bim/module/geometry/operator.py

@@ -329,7 +329,7 @@ class UpdateRepresentation(bpy.types.Operator, Operator):
                 "style.assign_representation_styles",
                 self.file,
                 shape_representation=new_representation,
-                styles=tool.Geometry.get_styles(obj),
+                styles=tool.Geometry.get_styles(obj, only_assigned_to_faces=True),
                 should_use_presentation_style_assignment=context.scene.BIMGeometryProperties.should_use_presentation_style_assignment,
             )
             tool.Geometry.record_object_materials(obj)

src/blenderbim/blenderbim/tool/geometry.py

@@ -396,8 +396,16 @@ class Geometry(blenderbim.core.tool.Geometry):
         return f"{representation.ContextOfItems.id()}/{representation.id()}"
 
     @classmethod
-    def get_styles(cls, obj):
-        return [tool.Style.get_style(s.material) for s in obj.material_slots if s.material]
+    def get_styles(cls, obj, only_assigned_to_faces=False):
+        styles = [tool.Style.get_style(s.material) for s in obj.material_slots if s.material]
+        if not only_assigned_to_faces:
+            return styles
+
+        usage_count = [0] * len(obj.material_slots)
+        for poly in obj.data.polygons:
+            usage_count[poly.material_index] += 1
+        styles = [style for style, usage in zip(styles, usage_count, strict=True) if usage > 0]
+        return styles
 
     # TODO: multiple Literals?
     @classmethod