FIX: always use at least 2 ticks and recompute

tacaswell · tacaswell · commit ea62a77634af · 2015-12-31T15:41:52.000-05:00
For extreme aspect-ratio plots the auto ntick logic would decide that
no ticks will fit, leading to divide by 0 issue.

 - In ticker ensure there is always at least on bin
 - Axis do 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 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 np.floor(length / size)
         return self._tick_space
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -1431,7 +1431,7 @@ def set_params(self, **kwargs):
     def bin_boundaries(self, vmin, vmax):
         nbins = self._nbins
         if nbins == 'auto':
-            nbins = min(self.axis.get_tick_space(), 9)
+            nbins = max(min(self.axis.get_tick_space(), 9), 1)
         scale, offset = scale_range(vmin, vmax, nbins)
         if self._integer:
             scale = max(1, scale)
