assign_representation_styles to reuse existing styled item + tests

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

@@ -47,8 +47,8 @@ class Usecase:
             showing up in Revit. In that case, set it to True, but keep in mind
             that this is no longer a valid IFC. Blame Autodesk.
         :type should_use_presentation_style_assignment: bool
-        :return: None
-        :rtype: None
+        :return: List of created IfcStyledItems
+        :rtype: ifcopenshell.entity_instance.entity_instance
 
         Example:
 
@@ -101,7 +101,10 @@ class Usecase:
     def execute(self):
         if not self.settings["styles"]:
             return []
+        self.settings["styles"] = self.settings["styles"].copy()
         self.results = []
+        use_style_assignment = self.file.schema == "IFC2X3" or self.settings["should_use_presentation_style_assignment"]
+
         for element in self.file.traverse(self.settings["shape_representation"]):
             if not element.is_a("IfcShapeRepresentation"):
                 continue
@@ -112,7 +115,34 @@ class Usecase:
                     # If there are more items than styles, fallback to using the last style
                     style = self.settings["styles"].pop(0)
                 name = style.Name
-                if self.file.schema == "IFC2X3" or self.settings["should_use_presentation_style_assignment"]:
+
+                # item may had previous styled item
+                prev_styled_item = next((i for i in item.StyledByItem), None)
+                if prev_styled_item is not None:
+                    # collect previously assigned styles
+                    assigned_styles = []
+                    style_assignment = None  # try to find some style assignment to reuse
+                    for style_ in prev_styled_item.Styles:
+                        if style_.is_a("IfcPresentationStyleAssignment"):
+                            if style_assignment is None:
+                                style_assignment = style_
+                            assigned_styles.extend(style_.Styles)
+                        else:  # IfcPresentationStyle
+                            assigned_styles.append(style_)
+
+                    if style not in assigned_styles:
+                        if use_style_assignment:
+                            if style_assignment is not None:
+                                style_assignment.Styles = style_assignment.Styles + (style,)
+                            else:
+                                style_assignment = self.file.createIfcPresentationStyleAssignment([style])
+                                prev_styled_item.Styles = prev_styled_item.Styles + (style_assignment,)
+                        else:
+                            prev_styled_item.Styles = prev_styled_item.Styles + (style,)
+                    # if style is in previous styles we also continue
+                    continue
+
+                if use_style_assignment:
                     style_assignment = self.file.createIfcPresentationStyleAssignment([style])
                     self.results.append(self.file.createIfcStyledItem(item, [style_assignment], name))
                 else:

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

@@ -0,0 +1,89 @@
+# 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 TestAssignRepresentationStyles(test.bootstrap.IFC4):
+    def test_run(self):
+        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        product_shape = self.file.createIfcProductDefinitionShape()
+        element.Representation = product_shape
+
+        representation = self.file.createIfcShapeRepresentation()
+        item = self.file.createIfcExtrudedAreaSolid()
+        representation.Items = [item]
+
+        style = self.file.createIfcSurfaceStyle()
+        ifcopenshell.api.run(
+            "style.assign_representation_styles", self.file, styles=[style], shape_representation=representation
+        )
+        assert item.StyledByItem[0].Styles == (style,)
+
+        # reusing existing styled item
+        style2 = self.file.createIfcSurfaceStyle()
+        ifcopenshell.api.run(
+            "style.assign_representation_styles", self.file, styles=[style2], shape_representation=representation
+        )
+        assert item.StyledByItem[0].Styles == (style, style2)
+        assert len(self.file.by_type("IfcStyledItem")) == 1
+
+    def test_assign_using_style_assignment(self):
+        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        product_shape = self.file.createIfcProductDefinitionShape()
+        element.Representation = product_shape
+
+        representation = self.file.createIfcShapeRepresentation()
+        item = self.file.createIfcExtrudedAreaSolid()
+        representation.Items = [item]
+
+        style = self.file.createIfcSurfaceStyle()
+        ifcopenshell.api.run(
+            "style.assign_representation_styles",
+            self.file,
+            styles=[style],
+            shape_representation=representation,
+            should_use_presentation_style_assignment=True,
+        )
+        assert len(self.file.by_type("IfcPresentationStyleAssignment")) == 1
+        style_assignment = self.file.by_type("IfcPresentationStyleAssignment")[0]
+        assert style_assignment.Styles == (style,)
+        assert item.StyledByItem[0].Styles == (style_assignment,)
+
+        # reusing existing styled item and style assignment
+        style2 = self.file.createIfcSurfaceStyle()
+        ifcopenshell.api.run(
+            "style.assign_representation_styles",
+            self.file,
+            styles=[style2],
+            shape_representation=representation,
+            should_use_presentation_style_assignment=True,
+        )
+
+        assert len(self.file.by_type("IfcPresentationStyleAssignment")) == 1
+        assert item.StyledByItem[0].Styles == (style_assignment,)
+        assert item.StyledByItem[0].Styles[0].Styles == (style, style2)
+        assert len(self.file.by_type("IfcStyledItem")) == 1
+
+
+class TestAssignRepresentationStylesIFC2X3(test.bootstrap.IFC2X3):
+    def test_run(self):
+        TestAssignRepresentationStyles.test_assign_using_style_assignment(self)