Reduce the floating point slop allowance in selecting ticks to show.

efiring · efiring · commit 2ac8e47608c7 · 2018-09-04T09:44:47.000-10:00
In #1686 this was set to half a pixel, but I don't think this makes sense, and it is not needed in order to pass the test that was added to check for lost ticks (#1310), or for the cases in #1310.
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -1053,9 +1053,7 @@ def _update_ticks(self, renderer):
             tick_tups = [ti for ti in tick_tups if ilow <= ti[1] <= ihigh]
 
         # so that we don't lose ticks on the end, expand out the interval ever
-        # so slightly.  The "ever so slightly" is defined to be the width of a
-        # half of a pixel.  We don't want to draw a tick that even one pixel
-        # outside of the defined axis interval.
+        # so slightly to compensate for floating point slop.
         if interval[0] <= interval[1]:
             interval_expanded = interval
         else:
@@ -1076,8 +1074,8 @@ def _update_ticks(self, renderer):
             with np.errstate(invalid='ignore'):
                 try:
                     ds1 = self._get_pixel_distance_along_axis(
-                        interval_expanded[0], -0.5)
-                except Exception:
+                        interval_expanded[0], -0.0005)
+                except:
                     warnings.warn("Unable to find pixel distance along axis "
                                   "for interval padding of ticks; assuming no "
                                   "interval padding needed.")
@@ -1086,8 +1084,8 @@ def _update_ticks(self, renderer):
                     ds1 = 0.0
                 try:
                     ds2 = self._get_pixel_distance_along_axis(
-                        interval_expanded[1], +0.5)
-                except Exception:
+                        interval_expanded[1], +0.0005)
+                except:
                     warnings.warn("Unable to find pixel distance along axis "
                                   "for interval padding of ticks; assuming no "
                                   "interval padding needed.")
