Fix axis inversion with loglocator and logitlocator.

anntzer · anntzer · commit 0e94bb921556 · 2019-08-19T21:26:42.000+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
@@ -47,9 +47,3 @@ properties of the `.Collection` object:
 While this seems complicated, the logic is simply to use the information from
 the object that are in data space for the limits, but not information that is
 in physical units.
-
-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/dates.py b/lib/matplotlib/dates.py
@@ -1117,8 +1117,9 @@ 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:
@@ -1336,6 +1337,8 @@ 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/ticker.py b/lib/matplotlib/ticker.py
@@ -2495,9 +2495,7 @@ 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.
@@ -2515,8 +2513,6 @@ 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
 
 
