Added screw threads to most things that are threaded.

Added a mechanism for tests.py and views.py to have command line options.

scripts/options.py

@@ -0,0 +1,49 @@
+#
+# NopSCADlib Copyright Chris Palmer 2020
+# nop.head@gmail.com
+# hydraraptor.blogspot.com
+#
+# This file is part of NopSCADlib.
+#
+# NopSCADlib is free software: you can redistribute it and/or modify it under the terms of the
+# GNU General Public License as published by the Free Software Foundation, either version 3 of
+# the License, or (at your option) any later version.
+#
+# NopSCADlib is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+# without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with NopSCADlib.
+# If not, see <https://www.gnu.org/licenses/>.
+#
+
+# Set command line options from enviroment variables and check if they have changed
+
+import json, os, deps
+
+def check_options(dir = '.'):
+    global options, options_mtime
+    options = { "show_threads": str(os.getenv("SHOW_THREADS")) }
+    options_fname = dir + '/options.json'
+    try:
+        with open(options_fname) as json_file:
+            last_options = json.load(json_file)
+    except:
+        last_options = {}
+    if last_options != options:
+        with open(options_fname, 'w') as outfile:
+            json.dump(options, outfile, indent = 4)
+    options_mtime = deps.mtime(options_fname)
+
+def have_changed(changed, target):
+    if not changed and deps.mtime(target) < options_mtime:
+        return "command line options changed"
+    return changed
+
+def list():
+    result = []
+    for name in options.keys():
+        value = options[name]
+        if value != 'None':
+            result.append('-D$' + name + '=' + value)
+    return result