Prevent axis related plot crash when plot is resized too small (#848)

* dont raise if datalow > datahigh

* additional NaN checking in auto_ticks

* add some logging about the bad range coming from the mappper

* better warning message

chaco/axis.py

@@ -10,6 +10,8 @@
 
 """ Defines the PlotAxis class, and associated validator and UI.
 """
+import logging
+
 # Major library import
 from numpy import (
     array,
@@ -58,6 +60,8 @@
 from .label import Label
 from .log_mapper import LogMapper
 
+logger = logging.getLogger(__name__)
+
 
 def DEFAULT_TICK_FORMATTER(val):
     return ("%f" % val).rstrip("0").rstrip(".")
@@ -500,20 +504,21 @@ def _compute_tick_positions(self, gc, overlay_component=None):
             screenlow, screenhigh = screenhigh, screenlow
 
         if (
-            (datalow == datahigh)
+            (datalow >= datahigh)
             or (screenlow == screenhigh)
             or (datalow in [inf, -inf])
             or (datahigh in [inf, -inf])
         ):
+            if datalow > datahigh:
+                logger.warning(
+                    "{self.mapper} has an invalid data range with "
+                    "low={datalow} > high={datahigh}; unable to compute axis "
+                    "ticks."
+                )
             self._reset_cache()
             self._cache_valid = True
             return
 
-        if datalow > datahigh:
-            raise RuntimeError(
-                "DataRange low is greater than high; unable to compute axis ticks."
-            )
-
         if not self.tick_generator:
             return
 

chaco/ticks.py

@@ -305,6 +305,8 @@ def auto_ticks(
 
     if upper > end:
         end += tick_interval
+    if isnan([start, end]).any():
+        return []
     ticks = arange(start, end + (tick_interval / 2.0), tick_interval)
 
     if len(ticks) < 2: