add surface styles preview (based on their blender materials)

Example - https://i.imgur.com/jH9q7iF.png

src/bonsai/bonsai/bim/module/style/data.py

@@ -44,13 +44,13 @@ class StylesData:
         cls.is_loaded = True
 
     @classmethod
-    def styles_to_blender_material_names(cls):
+    def styles_to_blender_material_names(cls) -> dict[bpy.types.PropertyGroup, Union[str, None]]:
         ifc_file = tool.Ifc.get()
         props = bpy.context.scene.BIMStylesProperties
-        materials = []
+        materials: dict[bpy.types.PropertyGroup, Union[str, None]] = {}
         for style in props.styles:
             material = tool.Ifc.get_object(ifc_file.by_id(style.ifc_definition_id))
-            materials.append(material.name if material is not None else None)
+            materials[style] = material.name if material is not None else None
         return materials
 
     @classmethod

src/bonsai/bonsai/bim/module/style/ui.py

@@ -22,6 +22,7 @@ import bonsai.tool as tool
 from bpy.types import Panel, UIList
 from bonsai.bim.ifc import IfcStore
 from bonsai.bim.module.style.data import StylesData, BlenderMaterialStyleData
+from typing import Union
 
 
 class BIM_PT_styles(Panel):
@@ -93,7 +94,7 @@ class BIM_PT_styles(Panel):
         # style ui tools
         if active_style:
             row = self.layout.row(align=True)
-            material_name = StylesData.data["styles_to_blender_material_names"][self.props.active_style_index]
+            material_name = StylesData.data["styles_to_blender_material_names"][style]
             if material_name:  # The user may have unlinked the style, so the material may not exist
                 material = bpy.data.materials[material_name]
                 row.prop(material.BIMStyleProperties, "active_style_type", icon="SHADING_RENDERED", text="")
@@ -266,7 +267,12 @@ class BIM_UL_styles(UIList):
     def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
         if item:
             row = layout.row(align=True)
-            row.prop(item, "name", text="", emboss=False)
+            material_name: Union[str, None] = StylesData.data["styles_to_blender_material_names"][item]
+            material_icon = 0
+            if material_name and (material := bpy.data.materials.get(material_name)):
+                preview = material.preview_ensure()
+                material_icon = preview.icon_id
+            row.prop(item, "name", text="", emboss=False, icon_value=material_icon)
             if item.has_surface_colour:
                 row = row.row(align=True)
                 row.enabled = False