matplotlib · QuLogic · Nov 26, 2021 · Nov 24, 2021 · Nov 25, 2021
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -12,6 +12,7 @@
 
 from collections import defaultdict
 import functools
+import inspect
 import itertools
 import math
 from numbers import Integral
@@ -412,24 +413,27 @@ def do_3d_projection(artist):
                 Call `do_3d_projection` on an *artist*, and warn if passing
                 *renderer*.
 
-                For our Artists, never pass *renderer*. For external Artists,
-                in lieu of more complicated signature parsing, always pass
-                *renderer* and raise a warning.
+                Attempt to bind the empty signature first, so external Artists
+                can avoid the deprecation warning if they support the new
+                calling convention.
                 """
-
-                if artist.__module__ == 'mpl_toolkits.mplot3d.art3d':
-                    # Our 3D Artists have deprecated the renderer parameter, so
-                    # avoid passing it to them; call this directly once the
-                    # deprecation has expired.
+                try:
+                    signature = inspect.signature(artist.do_3d_projection)
+                    signature.bind()
+                # ValueError if `inspect.signature` cannot provide a signature
+                # and TypeError if the binding fails or the object does not
+                # appear to be callable - the next call will then re-raise.
+                except (ValueError, TypeError):
+                    _api.warn_deprecated(
+                        "3.4",
+                        message="The 'renderer' parameter of "
+                        "do_3d_projection() was deprecated in Matplotlib "
+                        "%(since)s and will be removed %(removal)s.")
+                    return artist.do_3d_projection(renderer)
+                else:
+                    # Call this directly once the deprecation period expires.
                     return artist.do_3d_projection()
 
-                _api.warn_deprecated(
-                    "3.4",
-                    message="The 'renderer' parameter of "
-                    "do_3d_projection() was deprecated in Matplotlib "
-                    "%(since)s and will be removed %(removal)s.")
-                return artist.do_3d_projection(renderer)
-
             collections_and_patches = (
                 artist for artist in self._children
                 if isinstance(artist, (mcoll.Collection, mpatches.Patch))

diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -1711,3 +1711,63 @@ def test_view_init_vertical_axis(
         tickdir_expected = tickdirs_expected[i]
         tickdir_actual = axis._get_tickdir()
         np.testing.assert_array_equal(tickdir_expected, tickdir_actual)
+
+
+def test_do_3d_projection_renderer_deprecation_warn_on_argument():
+    """
+    Test that an external artist with an old-style calling convention raises
+    a suitable deprecation warning.
+    """
+    class DummyPatch(art3d.Patch3D):
+        def do_3d_projection(self, renderer):
+            return 0
+
+        def draw(self, renderer):
+            pass
+
+    fig = plt.figure()
+    ax = fig.add_subplot(111, projection='3d')
+    artist = DummyPatch()
+    ax.add_artist(artist)
+
+    match = r"The 'renderer' parameter of do_3d_projection\(\) was deprecated"
+    with pytest.warns(MatplotlibDeprecationWarning, match=match):
+        fig.canvas.draw()
+
+
+def test_do_3d_projection_renderer_deprecation_nowarn_on_optional_argument():
+    """
+    Test that an external artist with a calling convention compatible with
+    both v3.3 and v3.4 does not raise a deprecation warning.
+    """
+    class DummyPatch(art3d.Patch3D):
+        def do_3d_projection(self, renderer=None):
+            return 0
+
+        def draw(self, renderer):
+            pass
+
+    fig = plt.figure()
+    ax = fig.add_subplot(111, projection='3d')
+    artist = DummyPatch()
+    ax.add_artist(artist)
+    fig.canvas.draw()
+
+
+def test_do_3d_projection_renderer_deprecation_nowarn_on_no_argument():
+    """
+    Test that an external artist with a calling convention compatible with
+    only v3.4 does not raise a deprecation warning.
+    """
+    class DummyPatch(art3d.Patch3D):
+        def do_3d_projection(self):
+            return 0
+
+        def draw(self, renderer):
+            pass
+
+    fig = plt.figure()
+    ax = fig.add_subplot(111, projection='3d')
+    artist = DummyPatch()
+    ax.add_artist(artist)
+    fig.canvas.draw()