fix for must restart blender when installing

Author: losanc

__init__.py

@@ -55,6 +55,11 @@ def register():
     bpy.types.Mesh.SIMLOADER = bpy.props.PointerProperty(type=SIMLOADER_mesh_property)
 
 
+    # manually call this function once
+    # so when addon being installed, it can run correctly
+    # because scene is not used, so pass None into it
+    SIMLOADER_initilize(None)
+
 def unregister():
     for cls in classes:
         bpy.utils.unregister_class(cls)

simloader/messanger.py

@@ -13,10 +13,12 @@ def selected_callback():
 
 
 def subscribe_to_selected():
-    # A known problem of this function,
-    # This function will not be executed, when the first time this addon is installed.
-    # It will start to work, e.g. restart the blender, then in `load_post` function, this function will be called and start to work
     import simloader
+    
+    # because current implementation may subscribe twice
+    # so clear once to avoid duplication
+    bpy.msgbus.clear_by_owner(simloader)
+
     bpy.msgbus.subscribe_rna(
         key=(bpy.types.LayerObjects, 'active'),
         #  don't know why it needs this owner, so I set owner to this module `simloader`