OpenSCAD: Rewrite fixVisibility() to use rootObj

The original algorithm tried to use a heuristic to calculate which
objects should be shown or hidden, based on the object name. This commit
replaces that heurstic with a request for the list of root objects from
FreeCAD, which is then filtered to remove those that existed before the
import. Any descendant of those root objects is hidden, and the root
made visible, in keeping with the design of the CSG importer.

src/Mod/OpenSCAD/importCSG.py

@@ -52,6 +52,7 @@
 
 hassetcolor=[]
 alreadyhidden=[]
+original_root_objects = []
 
 # Get the token map from the lexer.  This is required.
 import tokrules
@@ -83,14 +84,15 @@ def setColorRecursively(obj, color, transp):
                 setColorRecursively(currentObject, color, transp)
 
 def fixVisibility():
-    for obj in FreeCAD.ActiveDocument.Objects:
-         if(( obj.TypeId=="Part::Fuse" or obj.TypeId=="Part::MultiFuse") and shallHide(obj)):
-            if "Group" in obj.FullName:
-                alreadyhidden.append(obj)
+    # After an import, only the remaining root objects that we created should be visible, not any 
+    # of their individual component objects. But make sure to only handle the ones we just imported,
+    # not anything that already existed. And objects that exist at the toplevel without any
+    # children are ignored.
+    for root_object in FreeCAD.ActiveDocument.RootObjects:
+        if root_object not in original_root_objects:
+            root_object.ViewObject.Visibility=True
+            for obj in root_object.OutListRecursive:
                 obj.ViewObject.Visibility=False
-                for currentObject in obj.OutList:
-                    if(currentObject not in alreadyhidden):
-                        currentObject.ViewObject.Visibility=True
 
 if gui:
     try:
@@ -135,6 +137,8 @@ def insert(filename,docname):
     groupname_unused = os.path.splitext(os.path.basename(filename))[0]
     try:
         doc=FreeCAD.getDocument(docname)
+        for obj in doc.RootObjects:
+            original_root_objects.append(obj)
     except NameError:
         doc=FreeCAD.newDocument(docname)
     #importgroup = doc.addObject("App::DocumentObjectGroup",groupname)