Simple support for API listeners for parametric IFC authoring - editing any parameter can now trigger events from a "parametric engine" which synchronises other related geometry and attributes in the IFC dataset. Implement auto box generation as a first demo.

src/ifcopenshell-python/ifcopenshell/api/__init__.py

@@ -1,11 +1,38 @@
 import importlib
+import ifcopenshell
 import ifcopenshell.api
 
 
-def run(usecase_path, ifc_file=None, **settings):
+registered_ifcs = {}
+pre_listeners = {}
+post_listeners = {}
+
+
+def run(usecase_path, ifc_file=None, should_run_listeners=True, **settings):
+    ifc_key = registered_ifcs.setdefault(ifc_file, ifcopenshell.guid.new())
+
+    if should_run_listeners:
+        for listener in pre_listeners.get(".".join([ifc_key, usecase_path]), []):
+            listener(usecase_path, ifc_file, **settings)
     importlib.import_module(f"ifcopenshell.api.{usecase_path}")
     module, usecase = usecase_path.split(".")
     usecase_class = getattr(getattr(getattr(ifcopenshell.api, module), usecase), "Usecase")
+
     if ifc_file:
-        return usecase_class(ifc_file, **settings).execute()
-    return usecase_class(**settings).execute()
+        result = usecase_class(ifc_file, **settings).execute()
+    else:
+        result = usecase_class(**settings).execute()
+
+    if should_run_listeners:
+        for listener in post_listeners.get(".".join([ifc_key, usecase_path]), []):
+            listener(usecase_path, ifc_file, **settings)
+    return result
+
+
+def add_pre_listener(usecase_path, ifc_file, callback):
+    ifc_key = registered_ifcs.setdefault(ifc_file, ifcopenshell.guid.new())
+    pre_listeners.setdefault(".".join([ifc_key, usecase_path]), set()).add(callback)
+
+def add_post_listener(usecase_path, ifc_file, callback):
+    ifc_key = registered_ifcs.setdefault(ifc_file, ifcopenshell.guid.new())
+    post_listeners.setdefault(".".join([ifc_key, usecase_path]), set()).add(callback)