SketchWidget takes window parameter

SketchWidget.py

@@ -9,8 +9,9 @@ from shapes import *
 from constraints import *
 
 class SketchWidget:
-    def __init__(self, sketch):
+    def __init__(self, sketch, window):
         self.sketch = sketch
+        self.window = window
         self.view_center = (0, 0)
         self.view_width = 4.0
         self.size = (1, 1)

Window.py

@@ -52,7 +52,7 @@ class Window:
 
         s.solve()
 
-        sw = SketchWidget(s)
+        sw = SketchWidget(s, self.window)
         self.window.add(sw.widget)
         self.window.show_all()