raise if num ticks exceeds some threshold to address sf bug 2715172

jdh2358 · jdh2358 · commit 0022de240f91 · 2009-09-07T18:42:41.000Z
svn path=/trunk/matplotlib/; revision=7676
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -522,6 +522,8 @@ def __call__(self):
 
         self.rule.set(dtstart=start, until=stop)
         dates = self.rule.between(dmin, dmax, True)
+        if len(dates)>=ticker.Locator.MAXTICKS:
+           raise RuntimeError('RRuleLocator attempting to generate %d ticks from %s to %s: exceeds matplotlib.ticker.Locator.MAXTICKS'%(len(dates), dates[0], dates[-1]))
         return date2num(dates)
 
     def _get_unit(self):
diff --git a/lib/matplotlib/tests/test_dates.py b/lib/matplotlib/tests/test_dates.py
@@ -1,6 +1,6 @@
 import datetime
 import numpy as np
-from matplotlib.testing.decorators import image_comparison
+from matplotlib.testing.decorators import image_comparison, knownfailureif
 import matplotlib.pyplot as plt
 
 @image_comparison(baseline_images=['date_empty'])
@@ -66,7 +66,10 @@ def test_date_axvline():
     fig.autofmt_xdate()
     fig.savefig('date_axvline')
 
-@image_comparison(baseline_images=['date_xlim_empty'])
+# we want to test that this method raises a RuntimeError -- what is
+# the rightway to do this in the current framework
+@knownfailureif(True)
+#@image_comparison(baseline_images=['date_xlim_empty'])
 def test_set_xlim_and_unexpected_handling():
     # Attempt to test SF 2715172, see
     # https://sourceforge.net/tracker/?func=detail&aid=2715172&group_id=80706&atid=560720
@@ -80,7 +83,7 @@ def test_set_xlim_and_unexpected_handling():
     ax.xaxis.set_major_locator(DayLocator())
     ax.xaxis.set_major_formatter(DateFormatter("%m/%d/%y, %I:%M%p"))
     ax.xaxis.set_minor_locator(HourLocator())
-    if 1:
+    if 0:
         # this seems to cause an ininite loop.
         from nose.plugins.skip import SkipTest
         raise SkipTest('avoiding never-ending drawing')
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -657,7 +657,14 @@ class Locator(TickHelper):
     because the locator stores references to the Axis data and view
     limits
     """
-
+    
+    # some automatic tick locators can generate so many ticks they
+    # kill the machine when you try and render them, see eg sf bug
+    # report
+    # https://sourceforge.net/tracker/index.php?func=detail&aid=2715172&group_id=80706&atid=560720.
+    # This parameter is set to cause locators to raise an error if too
+    # many ticks are generated
+    MAXTICKS = 1000
     def __call__(self):
         'Return the locations of the ticks'
         raise NotImplementedError('Derived must override')
diff --git a/lib/matplotlib/transforms.py b/lib/matplotlib/transforms.py
@@ -2266,6 +2266,7 @@ def nonsingular(vmin, vmax, expander=0.001, tiny=1e-15, increasing=True):
         else:
             vmin -= expander*abs(vmin)
             vmax += expander*abs(vmax)
+
     if swapped and not increasing:
         vmin, vmax = vmax, vmin
     return vmin, vmax
