fix handling of self-intersection

lib/extensions/convert_to_satin.py

@@ -5,6 +5,7 @@ import numpy
 from numpy import diff, sign, setdiff1d
 from scipy.signal import argrelmin
 import math
+from copy import deepcopy
 
 from .base import InkstitchExtension
 from ..svg.tags import SVG_PATH_TAG
@@ -40,6 +41,11 @@ class ConvertToSatin(InkstitchExtension):
                 except ValueError:
                     inkex.errormsg(_("Cannot convert %s to a satin column because it intersects itself.  Try breaking it up into multiple paths.") % element.node.get('id'))
 
+                    # revert any changes we've made
+                    self.document = deepcopy(self.original_document)
+
+                    return
+
                 parent.insert(index, self.satin_to_svg_node(rails, rungs, correction_transform))
 
             parent.remove(element.node)

messages.po

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PROJECT VERSION\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2018-07-30 16:03-0400\n"
+"POT-Creation-Date: 2018-07-30 16:40-0400\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -238,17 +238,17 @@ msgstr ""
 msgid "Please choose one or more commands to attach."
 msgstr ""
 
-#: lib/extensions/convert_to_satin.py:24
+#: lib/extensions/convert_to_satin.py:25
 msgid "Please select at least one line to convert to a satin column."
 msgstr ""
 
 #. : Convert To Satin extension, user selected one or more objects that were
 #. not lines.
-#: lib/extensions/convert_to_satin.py:29
+#: lib/extensions/convert_to_satin.py:30
 msgid "Only simple lines may be converted to satin columns."
 msgstr ""
 
-#: lib/extensions/convert_to_satin.py:41
+#: lib/extensions/convert_to_satin.py:42
 #, python-format
 msgid ""
 "Cannot convert %s to a satin column because it intersects itself.  Try "