assigning material styles to reuse existing styled item + tests

src/ifcopenshell-python/ifcopenshell/api/style/assign_material_style.py

@@ -114,6 +114,7 @@ class Usecase:
         else:
             self.create_new_definition_representation()
 
+        # handle material constituents and shape aspects
         material_constituents_names = []
         for inverse in self.file.get_inverse(self.settings["material"]):
             if inverse.is_a("IfcMaterialConstituent") and inverse.Name:
@@ -136,25 +137,28 @@ class Usecase:
                 )
 
     def modify_existing_definition_representation(self):
+        # NOTE: while it's theoritically possible to have multiple styles per 1 material
+        # (either with multiple styled items or multiple styles in 1 item)
+        # we use an implicit convention that
         definition_representation = self.settings["material"].HasRepresentation[0]
         representation = self.get_styled_representation(definition_representation)
         if representation:
-            potential_orphans = []
             items = list(representation.Items)
             new_items = []
-            removed_items = []
+            same_style_items = []
             for item in items:
                 if not item.is_a("IfcStyledItem"):
                     continue
                 if self.has_proposed_style(item):
                     return
                 if self.has_same_style_type(item):
-                    removed_items.append(item)
+                    same_style_items.append(item)
                 else:
                     new_items.append(item)
-            new_items.append(self.create_styled_item())
+            item_to_reuse = same_style_items.pop(0) if same_style_items else None
+            new_items.append(self.create_styled_item(item_to_reuse))
             representation.Items = new_items
-            for item in removed_items:
+            for item in same_style_items:
                 if len(self.file.get_inverse(item)) == 0:
                     self.file.remove(item)
         else:
@@ -172,7 +176,7 @@ class Usecase:
         representation = self.create_styled_representation()
         definition_representation = self.file.create_entity(
             "IfcMaterialDefinitionRepresentation",
-            **{"Representations": [representation], "RepresentedMaterial": self.settings["material"]}
+            **{"Representations": [representation], "RepresentedMaterial": self.settings["material"]},
         )
 
     def get_styled_representation(self, definition_representation):
@@ -191,8 +195,14 @@ class Usecase:
                 "ContextOfItems": self.settings["context"],
                 "RepresentationIdentifier": self.settings["context"].ContextIdentifier,
                 "Items": [self.create_styled_item()],
-            }
+            },
         )
 
-    def create_styled_item(self):
-        return self.file.create_entity("IfcStyledItem", **{"Styles": [self.style], "Name": self.settings["style"].Name})
+    def create_styled_item(self, reuse_item=None):
+        if reuse_item is None:
+            return self.file.create_entity(
+                "IfcStyledItem", **{"Styles": [self.style], "Name": self.settings["style"].Name}
+            )
+        reuse_item.Styles = (self.style,)
+        reuse_item.Name = self.settings["style"].Name
+        return reuse_item

src/ifcopenshell-python/ifcopenshell/api/style/unassign_material_style.py

@@ -49,7 +49,6 @@ class Usecase:
         }
 
     def execute(self):
-        to_delete = set()
         for definition in self.settings["material"].HasRepresentation:
             for representation in definition.Representations:
                 if not representation.is_a("IfcStyledRepresentation"):

src/ifcopenshell-python/test/api/style/test_assign_material_style.py

@@ -22,9 +22,35 @@ import ifcopenshell
 import ifcopenshell.api
 
 
-# TODO: test assigning styles without material constituents
 class TestAssignMaterialStyle(test.bootstrap.IFC4):
-    def test_update_shape_aspect_representaitons_items_styles_if_material_is_part_of_matching_material_constituents(
+    def test_run(self):
+        material = ifcopenshell.api.run("material.add_material", self.file)
+        context = self.file.createIfcGeometricRepresentationContext()
+        style = self.file.createIfcSurfaceStyle()
+        ifcopenshell.api.run("style.assign_material_style", self.file, material=material, style=style, context=context)
+
+        assert len(material.HasRepresentation) == 1
+        definition = material.HasRepresentation[0]
+        assert len(definition.Representations) == 1
+        representation = definition.Representations[0]
+        assert representation.is_a("IfcStyledRepresentation")
+        assert representation.ContextOfItems == context
+        assert len(representation.Items) == 1
+        item = representation.Items[0]
+        assert item.is_a("IfcStyledItem")
+        assert item.Styles == (style,)
+
+        style2 = self.file.createIfcSurfaceStyle()
+        ifcopenshell.api.run("style.assign_material_style", self.file, material=material, style=style2, context=context)
+
+        # reuse existing elements and reassign the style
+        assert material.HasRepresentation == (definition,)
+        assert definition.Representations == (representation,)
+        assert len(representation.Items) == 1
+        assert representation.Items[0] == item
+        assert representation.Items[0].Styles == (style2,)
+
+    def test_update_shape_aspect_representations_items_styles_if_material_is_part_of_matching_material_constituents(
         self,
     ):
         element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")

src/ifcopenshell-python/test/api/style/test_unassign_material_style.py

@@ -0,0 +1,47 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2022 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell 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 Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import pytest
+import test.bootstrap
+import ifcopenshell
+import ifcopenshell.api
+
+
+class TestAssignMaterialStyle(test.bootstrap.IFC4):
+    def test_run(self):
+        material = ifcopenshell.api.run("material.add_material", self.file)
+        context = self.file.createIfcGeometricRepresentationContext()
+        style = self.file.createIfcSurfaceStyle()
+        ifcopenshell.api.run("style.assign_material_style", self.file, material=material, style=style, context=context)
+
+        # unassign 1 style
+        style2 = self.file.createIfcSurfaceStyle()
+        item = self.file.by_type("IfcStyledItem")[0]
+        item.Styles = item.Styles + (style2,)
+        ifcopenshell.api.run(
+            "style.unassign_material_style", self.file, material=material, style=style2, context=context
+        )
+        assert item.Styles == (style,)
+
+        # unassign last style
+        ifcopenshell.api.run(
+            "style.unassign_material_style", self.file, material=material, style=style, context=context
+        )
+        assert len(self.file.by_type("IfcMaterialDefinitionRepresentation")) == 0
+        assert len(self.file.by_type("IfcStyledRepresentation")) == 0
+        assert len(self.file.by_type("IfcStyledItem")) == 0