Added Surround method to MObject, as well as special-case implementation of it to Circle

mobject/mobject.py

@@ -384,6 +384,10 @@ class Mobject(object):
         self.shift(mobject.get_center() - self.get_center())
         return self
 
+    def surround(self, mobject, dim_to_match = 0, stretch = False, buffer_factor = 1.2):
+        self.replace(mobject, dim_to_match, stretch)
+        self.scale_in_place(buffer_factor)
+
     def position_endpoints_on(self, start, end):
         curr_vect = self.points[-1] - self.points[0]
         if np.all(curr_vect == 0):

topics/geometry.py

@@ -47,6 +47,13 @@ class Circle(Arc):
     def __init__(self, **kwargs):
         Arc.__init__(self, 2*np.pi, **kwargs)
 
+    def surround(self, mobject, dim_to_match = 0, stretch = False, buffer_factor = 1.2):
+        # Ignores dim_to_match and stretch; result will always be a circle
+        # TODO: Perhaps create an ellipse class to handle singele-dimension stretching
+        self.replace(mobject, dim_to_match, stretch)
+        self.scale_to_fit_width(np.sqrt(mobject.get_width()**2 + mobject.get_height()**2))
+        self.scale(buffer_factor)
+
 class Dot(Circle):
     CONFIG = {
         "radius"       : 0.08,