Fix axis inversion with loglocator and logitlocator.

anntzer · anntzer · commit 177164d3bf6a · 2019-06-26T00:01:35.000+02:00
diff --git a/doc/api/next_api_changes/2019-03-04-AL.rst b/doc/api/next_api_changes/2019-03-04-AL.rst
@@ -12,9 +12,3 @@ without an explicit call to `Axes.autoscale_view`.
 
 In some cases, this can result in different limits being reported.  If this is
 an issue, consider triggering a draw with `fig.canvas.draw`.
-
-LogLocator.nonsingular now maintains the orders of its arguments
-````````````````````````````````````````````````````````````````
-
-It no longer reorders them in increasing order.  The new behavior is consistent
-with MaxNLocator.
diff --git a/doc/api/next_api_changes/2019-06-25-AL.rst b/doc/api/next_api_changes/2019-06-25-AL.rst
@@ -0,0 +1,7 @@
+API changes
+```````````
+
+`Locator.nonsingular` (introduced in mpl 3.1), `DateLocator.nonsingular`, and
+`AutoDateLocator.nonsingular` now returns a range ``v0, v1`` with ``v0 <= v1``.
+This behavior is consistent with the implementation of ``nonsingular`` by the
+`LogLocator` and `LogitLocator` subclasses.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -3266,8 +3266,11 @@ def set_xlim(self, left=None, right=None, emit=True, auto=False,
             cbook._warn_external(
                 f"Attempting to set identical left == right == {left} results "
                 f"in singular transformations; automatically expanding.")
+        swapped = left > right
         left, right = self.xaxis.get_major_locator().nonsingular(left, right)
         left, right = self.xaxis.limit_range_for_scale(left, right)
+        if swapped:
+            left, right = right, left
 
         self._viewLim.intervalx = (left, right)
         if auto is not None:
@@ -3647,8 +3650,11 @@ def set_ylim(self, bottom=None, top=None, emit=True, auto=False,
                 f"Attempting to set identical bottom == top == {bottom} "
                 f"results in singular transformations; automatically "
                 f"expanding.")
+        swapped = bottom > top
         bottom, top = self.yaxis.get_major_locator().nonsingular(bottom, top)
         bottom, top = self.yaxis.limit_range_for_scale(bottom, top)
+        if swapped:
+            bottom, top = top, bottom
 
         self._viewLim.intervaly = (bottom, top)
         if auto is not None:
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -1124,8 +1124,9 @@ def nonsingular(self, vmin, vmax):
         """
         Given the proposed upper and lower extent, adjust the range
         if it is too close to being singular (i.e. a range of ~0).
-
         """
+        if vmax < vmin:
+            vmin, vmax = vmax, vmin
         unit = self._get_unit()
         interval = self._get_interval()
         if abs(vmax - vmin) < 1e-6:
@@ -1342,6 +1343,8 @@ def tick_values(self, vmin, vmax):
     def nonsingular(self, vmin, vmax):
         # whatever is thrown at us, we can scale the unit.
         # But default nonsingular date plots at an ~4 year period.
+        if vmax < vmin:
+            vmin, vmax = vmax, vmin
         if vmin == vmax:
             vmin = vmin - DAYS_PER_YEAR * 2
             vmax = vmax + DAYS_PER_YEAR * 2
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -899,7 +899,12 @@ def test_inverted_limits():
 
     assert ax.get_xlim() == (-5, 4)
     assert ax.get_ylim() == (5, -3)
-    plt.close()
+
+    # Test inverting nonlinear axes.
+    fig, ax = plt.subplots()
+    ax.set_yscale("log")
+    ax.set_ylim(10, 1)
+    assert ax.get_ylim() == (10, 1)
 
 
 @image_comparison(['nonfinite_limits'])
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -1520,8 +1520,8 @@ def raise_if_exceeds(self, locs):
         return locs
 
     def nonsingular(self, v0, v1):
-        """Modify the endpoints of a range as needed to avoid singularities."""
-        return mtransforms.nonsingular(v0, v1, increasing=False, expander=.05)
+        """Expand a range as needed to avoid singularities."""
+        return mtransforms.nonsingular(v0, v1, expander=.05)
 
     def view_limits(self, vmin, vmax):
         """
@@ -2317,9 +2317,7 @@ def view_limits(self, vmin, vmax):
         return vmin, vmax
 
     def nonsingular(self, vmin, vmax):
-        swap_vlims = False
         if vmin > vmax:
-            swap_vlims = True
             vmin, vmax = vmax, vmin
         if not np.isfinite(vmin) or not np.isfinite(vmax):
             vmin, vmax = 1, 10  # Initial range, no data plotted yet.
@@ -2337,8 +2335,6 @@ def nonsingular(self, vmin, vmax):
             if vmin == vmax:
                 vmin = _decade_less(vmin, self._base)
                 vmax = _decade_greater(vmax, self._base)
-        if swap_vlims:
-            vmin, vmax = vmax, vmin
         return vmin, vmax
 
 
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -632,8 +632,11 @@ def set_xlim3d(self, left=None, right=None, emit=True, auto=False,
             cbook._warn_external(
                 f"Attempting to set identical left == right == {left} results "
                 f"in singular transformations; automatically expanding.")
+        swapped = left > right
         left, right = self.xaxis.get_major_locator().nonsingular(left, right)
         left, right = self.xaxis.limit_range_for_scale(left, right)
+        if swapped:
+            left, right = right, left
         self.xy_viewLim.intervalx = (left, right)
 
         if auto is not None:
@@ -690,8 +693,11 @@ def set_ylim3d(self, bottom=None, top=None, emit=True, auto=False,
                 f"Attempting to set identical bottom == top == {bottom} "
                 f"results in singular transformations; automatically "
                 f"expanding.")
+        swapped = bottom > top
         bottom, top = self.yaxis.get_major_locator().nonsingular(bottom, top)
         bottom, top = self.yaxis.limit_range_for_scale(bottom, top)
+        if swapped:
+            bottom, top = top, bottom
         self.xy_viewLim.intervaly = (bottom, top)
 
         if auto is not None:
@@ -748,8 +754,11 @@ def set_zlim3d(self, bottom=None, top=None, emit=True, auto=False,
                 f"Attempting to set identical bottom == top == {bottom} "
                 f"results in singular transformations; automatically "
                 f"expanding.")
+        swapped = bottom > top
         bottom, top = self.zaxis.get_major_locator().nonsingular(bottom, top)
         bottom, top = self.zaxis.limit_range_for_scale(bottom, top)
+        if swapped:
+            bottom, top = top, bottom
         self.zz_viewLim.intervalx = (bottom, top)
 
         if auto is not None:
