update plugin.

- sync PyBMap work. use different library name in different OS.
- add BMap encoding default value according to different OS (Windows and non-Windows) because non-Windows OS, we use libiconv as encoding converter.
- move all pointer properties to a single module and give corresponding visitor.
- add shared importer exporter parameters module thus bmfile import/export also can ref it.

bbp_ng/PROP_ptrprop_resolver.py

@@ -0,0 +1,51 @@
+import bpy
+
+## Intent
+#  Operator is not allowed to register Pointer Properties.
+#  The solution is register pointer properties in Scene and reference it when drawing operator window.
+#  This module contains all pointer properties used by other operators.
+
+class BBP_PG_ptrprop_resolver(bpy.types.PropertyGroup):
+    rail_uv_material: bpy.props.PointerProperty(
+        name = "Material",
+        description = "The material used for rail",
+        type = bpy.types.Material,
+    )
+    
+    export_collection: bpy.props.PointerProperty(
+        type = bpy.types.Collection,
+        name = "Collection",
+        description = "The collection exported. Nested collections allowed."
+    )
+    
+    export_object: bpy.props.PointerProperty(
+        type = bpy.types.Object,
+        name = "Object",
+        description = "The object exported"
+    )
+
+def get_ptrprop_resolver() -> BBP_PG_ptrprop_resolver:
+    return bpy.context.scene.bbp_ptrprop_resolver
+
+def get_rail_uv_material() -> bpy.types.Material:
+    return get_ptrprop_resolver().rail_uv_material
+def draw_rail_uv_material(layout: bpy.types.UILayout) -> None:
+    layout.prop(get_ptrprop_resolver(), 'rail_uv_material')
+
+def get_export_collection() -> bpy.types.Collection:
+    return get_ptrprop_resolver().export_collection
+def draw_export_collection(layout: bpy.types.UILayout) -> None:
+    layout.prop(get_ptrprop_resolver(), 'export_collection')
+
+def get_export_object() -> bpy.types.Object:
+    return get_ptrprop_resolver().export_object
+def draw_export_object(layout: bpy.types.UILayout) -> None:
+    layout.prop(get_ptrprop_resolver(), 'export_object')
+
+def register():
+    bpy.utils.register_class(BBP_PG_ptrprop_resolver)
+    bpy.types.Scene.bbp_ptrprop_resolver = bpy.props.PointerProperty(type = BBP_PG_ptrprop_resolver)
+
+def unregister():
+    del bpy.types.Scene.bbp_ptrprop_resolver
+    bpy.utils.unregister_class(BBP_PG_ptrprop_resolver)