Merge pull request matplotlib#18459 from meeseeksmachine/auto-backport-of-pr-18393-on-v3.3.x

Backport PR matplotlib#18393 on branch v3.3.x (Fix Axis scale on twinned Axes.)

Author: dopplershift

lib/matplotlib/axes/_base.py

@@ -490,8 +490,8 @@ def __init__(self, fig, rect,
         self._anchor = 'C'
         self._stale_viewlim_x = False
         self._stale_viewlim_y = False
-        self._sharex = None
-        self._sharey = None
+        self._sharex = sharex
+        self._sharey = sharey
         self.set_label(label)
         self.set_figure(fig)
         self.set_box_aspect(box_aspect)
@@ -510,11 +510,6 @@ def __init__(self, fig, rect,
         self._rasterization_zorder = None
         self.cla()
 
-        if sharex is not None:
-            self.sharex(sharex)
-        if sharey is not None:
-            self.sharey(sharey)
-
         # funcs used to format x and y - fall back on major formatters
         self.fmt_xdata = None
         self.fmt_ydata = None

lib/matplotlib/tests/test_axes.py

@@ -305,6 +305,50 @@ def test_twinx_cla():
     assert ax.yaxis.get_visible()
 
 
+@pytest.mark.parametrize('twin', ('x', 'y'))
+@check_figures_equal(extensions=['png'], tol=0.19)
+def test_twin_logscale(fig_test, fig_ref, twin):
+    twin_func = f'twin{twin}'  # test twinx or twiny
+    set_scale = f'set_{twin}scale'
+    x = np.arange(1, 100)
+
+    # Change scale after twinning.
+    ax_test = fig_test.add_subplot(2, 1, 1)
+    ax_twin = getattr(ax_test, twin_func)()
+    getattr(ax_test, set_scale)('log')
+    ax_twin.plot(x, x)
+
+    # Twin after changing scale.
+    ax_test = fig_test.add_subplot(2, 1, 2)
+    getattr(ax_test, set_scale)('log')
+    ax_twin = getattr(ax_test, twin_func)()
+    ax_twin.plot(x, x)
+
+    for i in [1, 2]:
+        ax_ref = fig_ref.add_subplot(2, 1, i)
+        getattr(ax_ref, set_scale)('log')
+        ax_ref.plot(x, x)
+
+        # This is a hack because twinned Axes double-draw the frame.
+        # Remove this when that is fixed.
+        Path = matplotlib.path.Path
+        fig_ref.add_artist(
+            matplotlib.patches.PathPatch(
+                Path([[0, 0], [0, 1],
+                      [0, 1], [1, 1],
+                      [1, 1], [1, 0],
+                      [1, 0], [0, 0]],
+                     [Path.MOVETO, Path.LINETO] * 4),
+                transform=ax_ref.transAxes,
+                facecolor='none',
+                edgecolor=mpl.rcParams['axes.edgecolor'],
+                linewidth=mpl.rcParams['axes.linewidth'],
+                capstyle='projecting'))
+
+    remove_ticks_and_titles(fig_test)
+    remove_ticks_and_titles(fig_ref)
+
+
 @image_comparison(['twin_autoscale.png'])
 def test_twinx_axis_scales():
     x = np.array([0, 0.5, 1])