closes:#6821 - This modification checks if the layer's material has a Category attribute and if it's not empty, then adds it as a CSS class with the format layer-material-category-{category_name}.

This will give you additional styling granularity when working with material layers, allowing you to target elements not just by their material name but also by their material category in your SVG styling.

src/bonsai/bonsai/bim/module/drawing/operator.py

@@ -1266,9 +1266,15 @@ class CreateDrawing(bpy.types.Operator):
 
         if layer:
             classes.append(layer.is_a())
-            material_name = layer.Material.Name or "null"
-            material_name = tool.Drawing.canonicalise_class_name(material_name)
-            classes.append(f"layer-material-{material_name}")
+            layer_material = layer.Material
+            layer_material_name = layer_material.Name or "null"
+            layer_material_name = tool.Drawing.canonicalise_class_name(layer_material_name)
+            classes.append(f"layer-material-{layer_material_name}")
+            
+            # Add material category if available
+            if hasattr(layer_material, 'Category') and layer_material.Category:
+                layer_material_category = tool.Drawing.canonicalise_class_name(layer_material.Category)
+                classes.append(f"layer-material-category-{layer_material_category}")
 
         for key in self.metadata:
             value = ifcopenshell.util.selector.get_element_value(element, key)