Fix axis inversion with loglocator and logitlocator.

anntzer · anntzer · commit df9c15236fc3 · 2019-08-06T21:17:44.000+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/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -3205,8 +3205,11 @@ 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:
@@ -3585,8 +3588,11 @@ 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
@@ -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/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
@@ -1697,8 +1697,8 @@ 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):
         """
@@ -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
 
 
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -616,8 +616,11 @@ 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:
@@ -674,8 +677,11 @@ 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:
@@ -732,8 +738,11 @@ 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:
