produce only one satin from convert to satin

2 files changed, 42 insertions, 5 deletions

diff --git a/lib/elements/satin_column.py b/lib/elements/satin_column.py
index 86c6d05a..cc0cda9f 100644
--- a/lib/elements/satin_column.py
+++ b/lib/elements/satin_column.py
@@ -825,6 +825,38 @@ class SatinColumn(EmbroideryElement):
 
         return SatinColumn(node)
 
+    def merge(self, satin):
+        """Merge this satin with another satin
+
+        This method expects that the provided satin continues on directly after
+        this one, as would be the case, for example, if the two satins were the
+        result of the split() method.
+
+        Returns a new SatinColumn instance that combines the rails and rungs of
+        this satin and the provided satin.  A rung is added at the end of this
+        satin.
+        """
+        rails = [self.flatten_subpath(rail) for rail in self.rails]
+        other_rails = [satin.flatten_subpath(rail) for rail in satin.rails]
+
+        if len(rails) != 2 or len(other_rails) != 2:
+            # weird non-satin things, give up and don't merge
+            return self
+
+        rails[0].extend(other_rails[0])
+        rails[1].extend(other_rails[1])
+
+        rungs = [self.flatten_subpath(rung) for rung in self.rungs]
+        other_rungs = [satin.flatten_subpath(rung) for rung in satin.rungs]
+
+        # add a rung at the end of my satin
+        rungs.append([rails[0][-1], rails[1][-1]])
+
+        # add on the other satin's rungs
+        rungs.extend(other_rungs)
+
+        return self._csp_to_satin(point_lists_to_csp(rails + rungs))
+
     @property
     @cache
     def center_line(self):
diff --git a/lib/extensions/convert_to_satin.py b/lib/extensions/convert_to_satin.py
index 7a36ce21..093b301c 100644
--- a/lib/extensions/convert_to_satin.py
+++ b/lib/extensions/convert_to_satin.py
@@ -13,7 +13,7 @@ from numpy import diff, setdiff1d, sign
 from shapely import geometry as shgeo
 
 from .base import InkstitchExtension
-from ..elements import Stroke
+from ..elements import SatinColumn, Stroke
 from ..i18n import _
 from ..svg import PIXELS_PER_MM, get_correction_transform
 from ..svg.tags import INKSTITCH_ATTRIBS
@@ -57,16 +57,21 @@ class ConvertToSatin(InkstitchExtension):
                     # ignore paths with just one point -- they're not visible to the user anyway
                     continue
 
-                for satin in self.convert_path_to_satins(path, element.stroke_width, style_args, correction_transform, path_style):
-                    parent.insert(index, satin)
-                    index += 1
+                satins = list(self.convert_path_to_satins(path, element.stroke_width, style_args, correction_transform, path_style))
+
+                if satins:
+                    joined_satin = satins[0]
+                    for satin in satins[1:]:
+                        joined_satin = joined_satin.merge(satin)
+
+                    parent.insert(index, joined_satin.node)
 
             parent.remove(element.node)
 
     def convert_path_to_satins(self, path, stroke_width, style_args, correction_transform, path_style, depth=0):
         try:
             rails, rungs = self.path_to_satin(path, stroke_width, style_args)
-            yield self.satin_to_svg_node(rails, rungs, correction_transform, path_style)
+            yield SatinColumn(self.satin_to_svg_node(rails, rungs, correction_transform, path_style))
         except SelfIntersectionError:
             # The path intersects itself.  Split it in two and try doing the halves
             # individually.