Fix alignment of offset text on top axis.

QuLogic · QuLogic · commit 64fdfcb7f6e4 · 2020-05-04T15:41:23.000-04:00
When set to show offset text on the top, the alignment is set to top,
but that's the same alignment as if it were on the bottom. It should be
set to bottom instead, or it will overlap with ticks.
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -2047,19 +2047,15 @@ def _update_offset_text_position(self, bboxes, bboxes2):
             else:
                 bbox = mtransforms.Bbox.union(bboxes)
                 bottom = bbox.y0
-            self.offsetText.set_position(
-                (x, bottom - self.OFFSETTEXTPAD * self.figure.dpi / 72)
-            )
+            y = bottom - self.OFFSETTEXTPAD * self.figure.dpi / 72
         else:
             if not len(bboxes2):
                 top = self.axes.bbox.ymax
             else:
                 bbox = mtransforms.Bbox.union(bboxes2)
                 top = bbox.y1
-            self.offsetText.set_va('top')
-            self.offsetText.set_position(
-                (x, top + self.OFFSETTEXTPAD * self.figure.dpi / 72)
-            )
+            y = top + self.OFFSETTEXTPAD * self.figure.dpi / 72
+        self.offsetText.set_position((x, y))
 
     def get_text_heights(self, renderer):
         """
@@ -2102,10 +2098,12 @@ def set_ticks_position(self, position):
             self.set_tick_params(which='both', top=True, labeltop=True,
                                  bottom=False, labelbottom=False)
             self._tick_position = 'top'
+            self.offsetText.set_verticalalignment('bottom')
         elif position == 'bottom':
             self.set_tick_params(which='both', top=False, labeltop=False,
                                  bottom=True, labelbottom=True)
             self._tick_position = 'bottom'
+            self.offsetText.set_verticalalignment('top')
         elif position == 'both':
             self.set_tick_params(which='both', top=True,
                                  bottom=True)
@@ -2116,6 +2114,7 @@ def set_ticks_position(self, position):
             self.set_tick_params(which='both', top=True, labeltop=False,
                                  bottom=True, labelbottom=True)
             self._tick_position = 'bottom'
+            self.offsetText.set_verticalalignment('top')
         else:
             assert False, "unhandled parameter not caught by _check_in_list"
         self.stale = True
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -4641,19 +4641,23 @@ def test_move_offsetlabel():
     ax.plot(data)
     fig.canvas.draw()
     before = ax.yaxis.offsetText.get_position()
+    assert ax.yaxis.offsetText.get_horizontalalignment() == 'left'
     ax.yaxis.tick_right()
     fig.canvas.draw()
     after = ax.yaxis.offsetText.get_position()
     assert after[0] > before[0] and after[1] == before[1]
+    assert ax.yaxis.offsetText.get_horizontalalignment() == 'right'
 
     fig, ax = plt.subplots()
     ax.plot(data)
     fig.canvas.draw()
     before = ax.xaxis.offsetText.get_position()
+    assert ax.xaxis.offsetText.get_verticalalignment() == 'top'
     ax.xaxis.tick_top()
     fig.canvas.draw()
     after = ax.xaxis.offsetText.get_position()
     assert after[0] == before[0] and after[1] > before[1]
+    assert ax.xaxis.offsetText.get_verticalalignment() == 'bottom'
 
 
 @image_comparison(['rc_spines.png'], savefig_kwarg={'dpi': 40})
