add get_bounds_nonempty

masque/pattern.py

@@ -568,6 +568,17 @@ class Pattern(LockableImpl, AnnotatableImpl, Mirrorable, metaclass=AutoSlots):
         else:
             return numpy.vstack((min_bounds, max_bounds))
 
+    def get_bounds_nonempty(self) -> NDArray[numpy.float64]:
+        """
+        Convenience wrapper for `get_bounds()` which asserts that the Pattern as non-None bounds.
+
+        Returns:
+            `[[x_min, y_min], [x_max, y_max]]`
+        """
+        bounds = self.get_bounds()
+        assert(bounds is not None)
+        return bounds
+
     def flatten(self: P) -> P:
         """
         Removes all subpatterns and adds equivalent shapes.

masque/shapes/path.py

@@ -332,7 +332,7 @@ class Path(Shape, metaclass=AutoSlots):
             bounds = numpy.array([[+inf, +inf], [-inf, -inf]])
             polys = self.to_polygons()
             for poly in polys:
-                poly_bounds = poly.get_bounds()
+                poly_bounds = poly.get_bounds_nonempty()
                 bounds[0, :] = numpy.minimum(bounds[0, :], poly_bounds[0, :])
                 bounds[1, :] = numpy.maximum(bounds[1, :], poly_bounds[1, :])
         else:

masque/traits/positionable.py

@@ -65,9 +65,21 @@ class Positionable(metaclass=ABCMeta):
     def get_bounds(self) -> Optional[NDArray[numpy.float64]]:
         """
         Returns `[[x_min, y_min], [x_max, y_max]]` which specify a minimal bounding box for the entity.
+        Returns `None` for an empty entity.
         """
         pass
 
+    def get_bounds_nonempty(self) -> NDArray[numpy.float64]:
+        """
+        Returns `[[x_min, y_min], [x_max, y_max]]` which specify a minimal bounding box for the entity.
+        Asserts that the entity is non-empty (i.e., `get_bounds()` does not return None).
+
+        This is handy for destructuring like `xy_min, xy_max = entity.get_bounds_nonempty()`
+        """
+        bounds = self.get_bounds()
+        assert(bounds is not None)
+        return bounds
+
 
 class PositionableImpl(Positionable, metaclass=ABCMeta):
     """