Sanity-check: skip glyphs with no area

They cause the python-poly2tri call to segfault, so skip them if
they exist.

Author: rmunn

extractpoints.py

@@ -28,7 +28,7 @@
 )
 from generalfuncs import (
     pairwise, by_threes, flatten,
-    vectorlength, are_points_equal, are_lines_equal,
+    vectorlength, are_points_equal, are_lines_equal, is_sane_contour,
     averagepoint_as_ffpoint, averagepoint_as_tuple, averagepoint_as_tuplevector,
     comp, iterfilter_stopatvectors, itermap_stopatvectors,
     AttrDict, closer, closerish, further, angle, similar_direction, shallow_angle,
@@ -572,6 +572,10 @@ def extract_dots(glyph, show_glyph=True):
     # Extract vectors with the real stroke width now
     approx_outlines = []
     for contour in layer:
+        if not is_sane_contour(contour):
+            print("Skipping invalid contour:")
+            print(", ".join(str((p.x, p.y)) for p in contour))
+            continue
         points = extrapolate_midpoints(list(contour))
         approx_vectors = extract_vectors(points)
         linestring = vectorpairs_to_linestring(approx_vectors)
@@ -657,7 +661,10 @@ def make_triangles(polygon_data, holes = None):
     new_polyline = convert_polyline_to_polytri_version(polygon_data['line'])
     if are_points_equal(new_polyline[-1], new_polyline[0]):
         del new_polyline[-1]
+    #print("About to call p2t with polyline:")
+    #print(", ".join(str((p.x, p.y)) for p in new_polyline))
     cdt = p2t.CDT(new_polyline)
+    #print("Just called p2t")
     for hole_data in holes:
         hole = hole_data['line']
         if hasattr(hole, 'coords'):

generalfuncs.py

@@ -33,6 +33,18 @@ def vectorlength(point1, point2):
     length = squaredlength**0.5
     return length
 
+def is_sane_contour(contour):
+    """Takes a contour in Fontforge format, and makes sure that it's sane.
+    One way contours can be insane is if all their points have the same x
+    coordinate, or the same y coordinate. This produces a glyph with no area,
+    which causes the poly2tri operation to segfault."""
+    x1, y1 = contour[0].x, contour[0].y
+    if (all(p.x == x1 for p in contour)):
+        return False
+    if (all(p.y == y1 for p in contour)):
+        return False
+    return True
+
 def ux(p):
     """Extract the x value of a point in any format"""
     try: