FIX: always use at least 2 ticks and recompute

tacaswell · tacaswell · commit 59abb91ab48d · 2015-12-31T11:55:21.000-05:00
For extreme aspect-ratio plots the auto ntick logic would decide that
no ticks will fit, leading to divide by 0 issue.

 - This changes the logic in Axis.get_tick_space to have a floor of 1.
 - also does not cache the number of ticks so that if the on-screen
   aspect ratio changes the number of ticks will update correctly.
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -2004,7 +2004,7 @@ def get_tick_space(self):
             # is no more than 3:1
             size = tick.label1.get_size() * 3
             size *= np.cos(np.deg2rad(tick.label1.get_rotation()))
-            self._tick_space = np.floor(length / size)
+            return max(1, np.floor(length / size))
         return self._tick_space
 
 
@@ -2346,5 +2346,5 @@ def get_tick_space(self):
             # Having a spacing of at least 2 just looks good.
             size = tick.label1.get_size() * 2.0
             size *= np.cos(np.deg2rad(tick.label1.get_rotation()))
-            self._tick_space = np.floor(length / size)
+            return max(1, np.floor(length / size))
         return self._tick_space
