Fix handling of zero-length line segments during pretty SVG export

Fixess gitlab issue #8

src/gerbonara/graphic_primitives.py

@@ -62,6 +62,12 @@ class GraphicPrimitive:
 
         raise NotImplementedError()
 
+    def is_zero_size(self):
+        """ Return whether this primitive is zero size
+
+        :rtype: bool
+        """
+
 
 @dataclass(frozen=True)
 class Circle(GraphicPrimitive):
@@ -84,6 +90,9 @@ class Circle(GraphicPrimitive):
                        [(True, (self.x, self.y)), (True, (self.x, self.y))],
                        polarity_dark=self.polarity_dark)
 
+    def is_zero_size(self):
+        return math.isclose(self.r, 0)
+
 
 @dataclass(frozen=True)
 class ArcPoly(GraphicPrimitive):
@@ -180,6 +189,20 @@ class ArcPoly(GraphicPrimitive):
         return self
 
 
+    def is_zero_size(self):
+        for (x1, y1), (x2, y2), (clockwise, (cx, cy)) in self.segments:
+            if clockwise is not None: # arc
+                if math.isclose(cx, x1) and math.isclose(cy, y1):
+                    continue
+                
+                if math.isclose(x1, x2) and math.isclose(y1, y2):
+                    return False
+
+        if math.isclose(polygon_area(self.outline), 0):
+            return True
+        return False
+
+
 @dataclass(frozen=True)
 class Line(GraphicPrimitive):
     """ Straight line with round end caps. """
@@ -244,6 +267,9 @@ class Line(GraphicPrimitive):
                     None,
                 ], polarity_dark=self.polarity_dark)
 
+    def is_zero_size(self):
+        return math.isclose(self.x1, self.x2) and math.isclose(self.y1, self.y2)
+
 
 @dataclass(frozen=True)
 class Arc(GraphicPrimitive):
@@ -310,6 +336,9 @@ class Arc(GraphicPrimitive):
                     (not self.clockwise, (self.cx, self.cy)),
                 ], polarity_dark=self.polarity_dark)
 
+    def is_zero_size(self):
+        return False # an arc with identical start and end points is defined as a circle
+
 
 @dataclass(frozen=True)
 class Rectangle(GraphicPrimitive):
@@ -345,3 +374,6 @@ class Rectangle(GraphicPrimitive):
         return tag('rect', x=prec(x), y=prec(y), width=prec(self.w), height=prec(self.h),
                 **svg_rotation(self.rotation, self.x, self.y), fill=color)
 
+    def is_zero_size(self):
+        return math.isclose(self.w, 0) or math.isclose(self.h, 0)
+

src/gerbonara/layers.py

@@ -1012,7 +1012,7 @@ class LayerStack:
             if use == 'mask':
                 objects.insert(0, tag('path', id='outline-path', d=self.outline_svg_d(unit=svg_unit), fill='white'))
             layers.append(tag('g', objects, id=f'l-{side}-{use}', filter=f'url(#f-{use})',
-                              fill=default_fill, stroke=default_stroke, **stroke_attrs,
+                              fill=default_fill, stroke=default_stroke, **stroke_attrs, fill_rule='evenodd',
                               **inkscape_attrs(f'{side} {use}'), transform=layer_transform))
 
         for i, layer in enumerate(self.drill_layers):
@@ -1284,6 +1284,7 @@ class LayerStack:
         maybe_allegro_hint = '' if self.generator != 'allegro' else ' This file looks like it was generated by Allegro/OrCAD. These tools produce quite mal-formed gerbers, and often export text on the outline layer. If you generated this file yourself, maybe try twiddling with the export settings.'
         polygons = []
         lines = [ obj.as_primitive(unit) for obj in self.outline.instance.objects if isinstance(obj, (go.Line, go.Arc)) ]
+        lines = [ prim for prim in lines if not prim.is_zero_size() ]
 
         by_x = sorted([ (obj.x1, obj) for obj in lines ] + [ (obj.x2, obj) for obj in lines ], key=lambda x: x[0])
         dist_sq = lambda x1, y1, x2, y2: (x2-x1)**2 + (y2-y1)**2

src/gerbonara/utils.py

@@ -605,6 +605,18 @@ def point_in_polygon(point, poly):
     return res
 
 
+def polygon_area(poly):
+    # https://en.wikipedia.org/wiki/Shoelace_formula
+
+    if not poly or len(poly) < 3:
+        return 0
+
+    acc = 0
+    for (x1, y1), (x2, y2) in zip(poly, poly[-1:] + poly):
+        acc += (y1 + y2) * (x1 - x2)
+    return acc/2
+
+
 def bbox_intersect(a, b):
     if a is None or b is None:
         return False

tests/test_layers.py

@@ -330,10 +330,12 @@ REFERENCE_DIRS = {
             'wc2-F_SilkS.gbr': 'top silk',
             'wc2.kicad_pcb': None,
         },
+    'zero-length-lines': {
+            }
     }
 
 @filter_syntax_warnings
-@pytest.mark.parametrize('ref_dir,file_map', list(REFERENCE_DIRS.items()))
+@pytest.mark.parametrize('ref_dir,file_map', [(k, v) for k, v in REFERENCE_DIRS.items() if v])
 def test_layer_classifier(ref_dir, file_map):
     path = reference_path(ref_dir)
     print('Reference path is', path)