create a setting to produce pythonOCC shapes for ifcopenshell.geom.iterator and -create_shape()

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

@@ -22,7 +22,33 @@ import sys
 
 from .. import ifcopenshell_wrapper
 
-settings = ifcopenshell_wrapper.settings
+def has_occ():
+    try: import OCC.BRepTools
+    except: return False
+    return True
+
+
+has_occ = has_occ()
+wrap_shape_creation = lambda settings, shape: shape
+if has_occ:
+    import occ_utils as utils
+    wrap_shape_creation = lambda settings, shape: utils.create_shape_from_serialization(shape) if getattr(settings, 'use_python_opencascade', False) else shape
+
+
+# Subclass the settings module to provide an additional
+# setting to enable pythonOCC when available
+class settings(ifcopenshell_wrapper.settings):
+    if has_occ:
+        USE_PYTHON_OPENCASCADE = -1
+        def set(self, *args):
+            setting, value = args
+            if setting == settings.USE_PYTHON_OPENCASCADE:
+                self.set(settings.USE_BREP_DATA, value)
+                self.set(settings.DISABLE_TRIANGULATION, value)
+                self.use_python_opencascade = value
+            else:
+                ifcopenshell_wrapper.settings.set(self, *args)
+
 
 # Hide templating precision to the user by choosing based on Python's 
 # internal float type. This is probably always going to be a double.
@@ -34,11 +60,15 @@ for ty in (ifcopenshell_wrapper.iterator_single_precision, ifcopenshell_wrapper.
 # Make sure people are able to use python's platform agnostic paths
 class iterator(_iterator):
     def __init__(self, settings, filename):
+        self.settings = settings
         _iterator.__init__(self, settings, os.path.abspath(filename))
+    if has_occ:
+        def get(self):
+            return wrap_shape_creation(self.settings, _iterator.get(self))
 
 
 def create_shape(settings, inst): 
-    return ifcopenshell_wrapper.create_shape(settings, inst.wrapped_data)
+    return wrap_shape_creation(settings, ifcopenshell_wrapper.create_shape(settings, inst.wrapped_data))
 
 
 def iterate(settings, filename):
@@ -47,3 +77,5 @@ def iterate(settings, filename):
         while True:
             yield it.get()
             if not it.next(): break
+
+