Modified the compositor once again so that the original caravel
project gets read in as a subcell and points to the GDS created by
"make ship";  then the fill patterns and the seal ring are placed
as siblings in the same top level cell.

scripts/compositor.py

diff --git a/scripts/compositor.py b/scripts/compositor.py
index 6e0d67b..8882bb8 100755
--- a/scripts/compositor.py
+++ b/scripts/compositor.py
@@ -99,19 +99,20 @@
     with open(magpath + '/compose_final.tcl', 'w') as ofile:
         print('#!/bin/env wish', file=ofile)
         print('drc off', file=ofile)
-        # print('gds read ../gds/user_project_wrapper', file=ofile)
-        # print('load ' + project + ' -dereference', file=ofile)
-        print('gds readonly true', file=ofile)
-        print('gds rescale false', file=ofile)
-        print('gds read ../gds/caravel', file=ofile)
+
+        # Read project from .mag but set GDS properties so that it points
+        # to the GDS file created by "make ship".
+        print('load ' + project + ' -dereference', file=ofile)
+        print('property GDS_FILE ../gds/' + project + '.gds', file=ofile)
+        print('property GDS_START 0', file=ofile)
         print('select top cell', file=ofile)
+        print('set bbox [box values]', file=ofile)
 
         # Ceate a cell to represent the generated fill.  There are
         # no magic layers corresponding to the fill shape data, and
         # it's gigabytes anyway, so we don't want to deal with any
         # actual data.  So it's just a placeholder.
 
-        print('set bbox [box values]', file=ofile)
         print('load ' + project_with_id + '_fill_pattern', file=ofile)
         print('snap internal', file=ofile)
         print('box values {*}$bbox', file=ofile)
@@ -120,9 +121,11 @@
         print('property GDS_START 0', file=ofile)
         print('property FIXED_BBOX "$bbox"', file=ofile)
 
-        # Now go back to the project top level and place the fill cell.
-        print('load ' + project, file=ofile)
-        print('select top cell', file=ofile)	
+        # Create a new project top level and place the fill cell.
+        print('load ' + project_with_id + ' -quiet', file=ofile)
+        print('box size 0 0', file=ofile)	
+        print('box position 6um 6um', file=ofile)	
+        print('getcell ' + project + ' child 0 0', file=ofile)
         print('getcell ' + project_with_id + '_fill_pattern child 0 0', file=ofile)
 
         # Move existing origin to (6um, 6um) for seal ring placement