matplotlib/matplotlib — pull request #1531 by pierre-haessig (2012-11-24 18:03:09+00:00)
Title: fix rendering slowdown with big invisible lines (issue #1256)

tiny change in Line2D.draw to return immediately if the line is not visible.
This avoids annoying rendering slowdown with *big* Line2D objects (say lines holding about 10**7 points)