Precomputed easing values.

When panning the star map it would be well to have a smooth animation
for the movement.

THese values are from easeInOutQuad at:

=> https://gist.github.com/gre/1650294

ui.py

@@ -26,6 +26,17 @@ import data, stars
 
 DARK_GRAY = '#222'
 
+
+ease = 0.0, 0.02, 0.08, 0.18, 0.32, 0.5, 0.68, 0.82, 0.92, 0.98, 1.0
+
+def eased(from_, to):
+    interval = to - from_
+    for e in ease:
+        yield round(from_ + interval * e)
+
+def eased_xy(from_x, from_y, to_x, to_y):
+    yield from zip(eased(from_x, to_x), eased(from_y, to_y))
+
 class App:
     '''
     A canvas with scrolling support.