Only allow set_adjustable("datalim") for axes with standard data ratios.

anntzer · anntzer · commit 2cc8e14aa191 · 2019-07-17T22:48:53.000+02:00
If an Axes subclass overrides get_data_ratio to anything else than
"ratio of data limits after application of scales" (e.g. Polar always
returns 1), then the data limits manipulation in apply_aspect won't
achieve the proper data ratio anyways, so disable setting adjustable to
"datalim" in that case.

For example, calling `axis("equal")` on polar axes (which also sets
adjustable to "datalim") will now error out instead of resulting in a
nonsensical plot.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -1317,11 +1317,19 @@ def set_adjustable(self, adjustable, share=False):
         """
         cbook._check_in_list(["box", "datalim"], adjustable=adjustable)
         if share:
-            axes = {*self._shared_x_axes.get_siblings(self),
-                    *self._shared_y_axes.get_siblings(self)}
+            axs = {*self._shared_x_axes.get_siblings(self),
+                   *self._shared_y_axes.get_siblings(self)}
         else:
-            axes = [self]
-        for ax in axes:
+            axs = [self]
+        if (adjustable == "datalim"
+                and any(getattr(ax.get_data_ratio, "__func__")
+                        != _AxesBase.get_data_ratio
+                        for ax in axs)):
+            # Limits adjustment by apply_aspect assumes that the axes' aspect
+            # ratio can be computed from the data limits and scales.
+            raise ValueError("Cannot set axes adjustable to 'datalim' for "
+                             "Axes which override 'get_data_ratio'")
+        for ax in axs:
             ax._adjustable = adjustable
         self.stale = True
 
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -4724,6 +4724,12 @@ def test_shared_with_aspect_3():
             assert round(expected, 4) == round(ax.get_aspect(), 4)
 
 
+def test_polar_not_datalim_adjustable():
+    ax = plt.figure().add_subplot(projection="polar")
+    with pytest.raises(ValueError):
+        ax.set_adjustable("datalim")
+
+
 @pytest.mark.parametrize('twin', ('x', 'y'))
 def test_twin_with_aspect(twin):
     fig, ax = plt.subplots()
