Added a strategy to stop losing ticks on the ends of an axis. The approach that is

Daniel Hyams · Daniel Hyams · commit 255f213cd9fc · 2013-01-19T19:08:34.000-05:00
used is to pad the interval that is being used to "clip" ticks from the axis because
they are off the end.

The padding is chosen specifically such that the tick cannot be drawn a pixel past the
end of the axis.  So long as the tick is within this bound, it should be OK to draw it.
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -972,11 +972,24 @@ def _update_ticks(self, renderer):
                 tick_tups = [ti for ti in tick_tups
                              if (ti[1] >= ilow) and (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.
+        if interval[0] <= interval[1]:
+            interval_expanded = interval
+        else:
+            interval_expanded = interval[1],interval[0]
+        
+        if hasattr(self,'_get_pixel_distance_along_axis'):
+            ds1 = self._get_pixel_distance_along_axis(interval_expanded[0],-1)/2.0
+            ds2 = self._get_pixel_distance_along_axis(interval_expanded[1],+1)/2.0
+            interval_expanded = (interval[0]-ds1,interval[1]+ds2)
+
         ticks_to_draw = []
         for tick, loc, label in tick_tups:
             if tick is None:
                 continue
-            if not mtransforms.interval_contains(interval, loc):
+            if not mtransforms.interval_contains(interval_expanded, loc):
                 continue
             tick.update_position(loc)
             tick.set_label1(label)
@@ -1599,6 +1612,24 @@ def _get_offset_text(self):
         self.offset_text_position = 'bottom'
         return offsetText
 
+    def _get_pixel_distance_along_axis(self,where,perturb):
+        # returns the amount, in data coordinates, that a single pixel corresponds to in the
+        # locality given by "where", which is also given in data coordinates, and is an x coordinate.
+        # "perturb" is the amount to perturb the pixel.  Usually +1 or -1.
+        
+        # first figure out the pixel location of the "where" point.  We use 1e-10 for the
+        # y point, so that we remain compatible with log axes.
+        #
+        # I THINK this will work too for polar axes, but I'm not 100% sure.
+        #
+        trans = self.axes.transData     # transformation from data coords to display coords
+        transinv = trans.inverted()     # transformation from display coords to data coords
+        pix  = trans.transform_point((where,1e-10))
+        ptp  = transinv.transform_point((pix[0]+perturb,pix[1])) # perturb the pixel.
+        dx   = abs(ptp[0]-where)
+        
+        return dx
+
     def get_label_position(self):
         """
         Return the label position (top or bottom)
@@ -1874,6 +1905,22 @@ def _get_offset_text(self):
         self.offset_text_position = 'left'
         return offsetText
 
+    def _get_pixel_distance_along_axis(self,where,perturb):
+        # returns the amount, in data coordinates, that a single pixel corresponds to in the
+        # locality given by "where", which is also given in data coordinates, and is a y coordinate.
+        # "perturb" is the amount to perturb the pixel.  Usually +1 or -1.
+        
+        # first figure out the pixel location of the "where" point.  We use 1e-10 for the
+        # x point, so that we remain compatible with log axes.
+        #
+        # I THINK this will work too for polar axes, but I'm not 100% sure.
+        #
+        trans = self.axes.transData     # transformation from data coords to display coords
+        transinv = trans.inverted()     # transformation from display coords to data coords
+        pix  = trans.transform_point((1e-10,where))
+        ptp  = transinv.transform_point((pix[0],pix[1]+perturb)) # perturb the pixel.
+        dy   = abs(ptp[1]-where)
+
     def get_label_position(self):
         """
         Return the label position (left or right)
