From fc0ee8f41b3f83402af7811fca9e5cae522802cd Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Mon, 30 Jun 2025 10:39:29 +0200
Subject: [PATCH] Backport PR #30223: Polar log scale: fix inner patch boundary
 and spine location

---
 lib/matplotlib/projections/polar.py |  8 +++++++-
 lib/matplotlib/spines.py            |  8 +++++++-
 lib/matplotlib/tests/test_polar.py  | 20 ++++++++++++++++++++
 lib/matplotlib/tests/test_spines.py | 12 ++++++++++++
 4 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/lib/matplotlib/projections/polar.py b/lib/matplotlib/projections/polar.py
index 7fe6045039b1..2630a7dac3aa 100644
--- a/lib/matplotlib/projections/polar.py
+++ b/lib/matplotlib/projections/polar.py
@@ -857,6 +857,10 @@ def _init_axis(self):
         self.xaxis = ThetaAxis(self, clear=False)
         self.yaxis = RadialAxis(self, clear=False)
         self.spines['polar'].register_axis(self.yaxis)
+        inner_spine = self.spines.get('inner', None)
+        if inner_spine is not None:
+            # Subclasses may not have inner spine.
+            inner_spine.register_axis(self.yaxis)
 
     def _set_lim_and_transforms(self):
         # A view limit where the minimum radius can be locked if the user
@@ -1002,7 +1006,9 @@ def draw(self, renderer):
         thetamin, thetamax = np.rad2deg(self._realViewLim.intervalx)
         if thetamin > thetamax:
             thetamin, thetamax = thetamax, thetamin
-        rmin, rmax = ((self._realViewLim.intervaly - self.get_rorigin()) *
+        rscale_tr = self.yaxis.get_transform()
+        rmin, rmax = ((rscale_tr.transform(self._realViewLim.intervaly) -
+                       rscale_tr.transform(self.get_rorigin())) *
                       self.get_rsign())
         if isinstance(self.patch, mpatches.Wedge):
             # Backwards-compatibility: Any subclassed Axes might override the
diff --git a/lib/matplotlib/spines.py b/lib/matplotlib/spines.py
index 7e77a393f2a2..9732a2f3347a 100644
--- a/lib/matplotlib/spines.py
+++ b/lib/matplotlib/spines.py
@@ -265,11 +265,17 @@ def _adjust_location(self):
                 self._path = mpath.Path.arc(np.rad2deg(low), np.rad2deg(high))
 
                 if self.spine_type == 'bottom':
-                    rmin, rmax = self.axes.viewLim.intervaly
+                    if self.axis is None:
+                        tr = mtransforms.IdentityTransform()
+                    else:
+                        tr = self.axis.get_transform()
+                    rmin, rmax = tr.transform(self.axes.viewLim.intervaly)
                     try:
                         rorigin = self.axes.get_rorigin()
                     except AttributeError:
                         rorigin = rmin
+                    else:
+                        rorigin = tr.transform(rorigin)
                     scaled_diameter = (rmin - rorigin) / (rmax - rorigin)
                     self._height = scaled_diameter
                     self._width = scaled_diameter
diff --git a/lib/matplotlib/tests/test_polar.py b/lib/matplotlib/tests/test_polar.py
index 87c8efe3045e..844ab8cf3a06 100644
--- a/lib/matplotlib/tests/test_polar.py
+++ b/lib/matplotlib/tests/test_polar.py
@@ -482,6 +482,26 @@ def test_polar_log():
     ax.plot(np.linspace(0, 2 * np.pi, n), np.logspace(0, 2, n))
 
 
+@check_figures_equal()
+def test_polar_log_rorigin(fig_ref, fig_test):
+    # Test that equivalent linear and log radial settings give the same axes patch
+    # and spines.
+    ax_ref = fig_ref.add_subplot(projection='polar', facecolor='red')
+    ax_ref.set_rlim(0, 2)
+    ax_ref.set_rorigin(-3)
+    ax_ref.set_rticks(np.linspace(0, 2, 5))
+
+    ax_test = fig_test.add_subplot(projection='polar', facecolor='red')
+    ax_test.set_rscale('log')
+    ax_test.set_rlim(1, 100)
+    ax_test.set_rorigin(10**-3)
+    ax_test.set_rticks(np.logspace(0, 2, 5))
+
+    for ax in ax_ref, ax_test:
+        # Radial tick labels should be the only difference, so turn them off.
+        ax.tick_params(labelleft=False)
+
+
 def test_polar_neg_theta_lims():
     fig = plt.figure()
     ax = fig.add_subplot(projection='polar')
diff --git a/lib/matplotlib/tests/test_spines.py b/lib/matplotlib/tests/test_spines.py
index 29b4ecf6f330..99b8461ad851 100644
--- a/lib/matplotlib/tests/test_spines.py
+++ b/lib/matplotlib/tests/test_spines.py
@@ -154,3 +154,15 @@ def test_spines_black_axes():
     ax.set_xticks([])
     ax.set_yticks([])
     ax.set_facecolor((0, 0, 0))
+
+
+def test_arc_spine_inner_no_axis():
+    # Backcompat: smoke test that inner arc spine does not need a registered
+    # axis in order to be drawn
+    fig = plt.figure()
+    ax = fig.add_subplot(projection="polar")
+    inner_spine = ax.spines["inner"]
+    inner_spine.register_axis(None)
+    assert ax.spines["inner"].axis is None
+
+    fig.draw_without_rendering()