Resolve issue 144

Added a test for the new mechanism
Added a gerber test file

FlatCAMApp.py

@@ -265,6 +265,7 @@ class App(QtCore.QObject):
             "point_clipboard_format": "(%.4f, %.4f)",
             "zdownrate": None,
             "excellon_zeros": "L",
+            "gerber_use_buffer_for_union": True,
             "cncjob_coordinate_format": "X%.4fY%.4f"
         })
 
@@ -1807,6 +1808,7 @@ class App(QtCore.QObject):
         routes = {
             "zdownrate": CNCjob,
             "excellon_zeros": Excellon,
+            "gerber_use_buffer_for_union": Gerber,
             "cncjob_coordinate_format": CNCjob
         }
 

camlib.py

@@ -1159,7 +1159,8 @@ class Gerber (Geometry):
     """
 
     defaults = {
-        "steps_per_circle": 40
+        "steps_per_circle": 40,
+        "use_buffer_for_union": True
     }
 
     def __init__(self, steps_per_circle=None):
@@ -1277,6 +1278,8 @@ class Gerber (Geometry):
         # How to discretize a circle.
         self.steps_per_circ = steps_per_circle or Gerber.defaults['steps_per_circle']
 
+        self.use_buffer_for_union = self.defaults["use_buffer_for_union"]
+
     def scale(self, factor):
         """
         Scales the objects' geometry on the XY plane by a given factor.
@@ -1964,8 +1967,15 @@ class Gerber (Geometry):
 
             # --- Apply buffer ---
             log.warn("Joining %d polygons." % len(poly_buffer))
-            new_poly = cascaded_union(poly_buffer)
-            new_poly = new_poly.buffer(0)
+            if (self.use_buffer_for_union):
+                new_poly = MultiPolygon(poly_buffer)
+                new_poly = new_poly.buffer(0.00000001)
+                new_poly = new_poly.buffer(-0.00000001)
+                log.warn("Union(buffer) done.")
+            else:
+                new_poly = cascaded_union(poly_buffer)
+                new_poly = new_poly = new_poly.buffer(0)
+                log.warn("Union done.")
             if current_polarity == 'D':
                 self.solid_geometry = self.solid_geometry.union(new_poly)
             else:

tests/test_gerber_buffer.py

@@ -0,0 +1,44 @@
+import unittest
+import camlib
+from shapely.geometry import Polygon, LineString, Point, LinearRing
+from shapely.geometry import MultiPoint, MultiPolygon
+from shapely.geometry import box as shply_box
+from shapely.ops import cascaded_union
+import shapely.affinity as affinity
+from shapely.wkt import loads as sloads
+from shapely.wkt import dumps as sdumps
+from shapely.geometry.base import BaseGeometry
+
+class GerberBuffer(unittest.TestCase):
+    def setUp(self):
+        self.gerber1 = camlib.Gerber()
+        self.gerber1.use_buffer_for_union = True
+        self.gerber1.parse_file ("./gerber_files/STM32F4-spindle.cmp")
+        geometry1 = self.gerber1.solid_geometry
+        self.geometry1_area = self.compute_area (geometry1)
+        self.gerber2 = camlib.Gerber()
+        self.gerber2.use_buffer_for_union = False
+        self.gerber2.parse_file ("./gerber_files/STM32F4-spindle.cmp")
+        geometry2 = self.gerber2.solid_geometry
+        self.geometry2_area = self.compute_area (geometry2)
+
+
+
+    def compute_area (self, geometry):
+        area = 0
+        try:
+            for geo in geometry:
+                area += geo.area
+
+        ## Not iterable, do the actual indexing and add.
+        except TypeError:
+            area = geometry.area
+        return area
+
+
+    def test_buffer(self):
+        self.assertLessEqual (abs(self.geometry2_area - self.geometry1_area), 0.000001)
+
+
+if __name__ == '__main__':
+    unittest.main()