matplotlib · efiring · Dec 25, 2020 · Jul 30, 2020 · Jul 31, 2020 · Jul 31, 2020
diff --git a/doc/api/next_api_changes/behavior/18127-ES.rst b/doc/api/next_api_changes/behavior/18127-ES.rst
@@ -0,0 +1,11 @@
+Autoscaling in Axes3D
+~~~~~~~~~~~~~~~~~~~~~
+
+In Matplotlib 3.2.0, autoscaling was made lazier for 2D Axes, i.e., limits
+would only be recomputed when actually rendering the canvas, or when the user
+queries the Axes limits. This performance improvement is now extended to
+`.Axes3D`. This also fixes some issues with autoscaling being triggered
+unexpectedly in Axes3D.
+
+Please see :ref:`the API change for 2D Axes <api-changes-3-2-0-autoscaling>`
+for further details.
diff --git a/doc/api/prev_api_changes/api_changes_3.2.0/behavior.rst b/doc/api/prev_api_changes/api_changes_3.2.0/behavior.rst
@@ -54,6 +54,8 @@ writer, without performing the availability check on subsequent writers, it is
 now possible to iterate over the registry, which will yield the names of the
 available classes.
 
+.. _api-changes-3-2-0-autoscaling:
+
 Autoscaling
 ~~~~~~~~~~~
 

diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -6717,34 +6717,24 @@ def test_ytickcolor_is_not_markercolor():
         assert tick.tick1line.get_markeredgecolor() != 'white'
 
 
+@pytest.mark.parametrize('axis', ('x', 'y'))
 @pytest.mark.parametrize('auto', (True, False, None))
-def test_unautoscaley(auto):
-    fig, ax = plt.subplots()
-    x = np.arange(100)
-    y = np.linspace(-.1, .1, 100)
-    ax.scatter(x, y)
-
-    post_auto = ax.get_autoscaley_on() if auto is None else auto
-
-    ax.set_ylim((-.5, .5), auto=auto)
-    assert post_auto == ax.get_autoscaley_on()
-    fig.canvas.draw()
-    assert_array_equal(ax.get_ylim(), (-.5, .5))
-
-
-@pytest.mark.parametrize('auto', (True, False, None))
-def test_unautoscalex(auto):
+def test_unautoscale(axis, auto):
     fig, ax = plt.subplots()
     x = np.arange(100)
     y = np.linspace(-.1, .1, 100)
     ax.scatter(y, x)
 
-    post_auto = ax.get_autoscalex_on() if auto is None else auto
+    get_autoscale_on = getattr(ax, f'get_autoscale{axis}_on')
+    set_lim = getattr(ax, f'set_{axis}lim')
+    get_lim = getattr(ax, f'get_{axis}lim')
+
+    post_auto = get_autoscale_on() if auto is None else auto
 
-    ax.set_xlim((-.5, .5), auto=auto)
-    assert post_auto == ax.get_autoscalex_on()
+    set_lim((-0.5, 0.5), auto=auto)
+    assert post_auto == get_autoscale_on()
     fig.canvas.draw()
-    assert_array_equal(ax.get_xlim(), (-.5, .5))
+    assert_array_equal(get_lim(), (-0.5, 0.5))
 
 
 @check_figures_equal(extensions=["png"])

diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -90,6 +90,7 @@ def __init__(
         self.zz_viewLim = Bbox.unit()
         self.xy_dataLim = Bbox.unit()
         self.zz_dataLim = Bbox.unit()
+        self._stale_viewlim_z = False
 
         # inhibit autoscale_view until the axes are defined
         # they can't be defined until Axes.__init__ has been called
@@ -191,6 +192,24 @@ def get_zaxis(self):
     def _get_axis_list(self):
         return super()._get_axis_list() + (self.zaxis, )
 
+    def _unstale_viewLim(self):
+        # We should arrange to store this information once per share-group
+        # instead of on every axis.
+        scalex = any(ax._stale_viewlim_x
+                     for ax in self._shared_x_axes.get_siblings(self))
+        scaley = any(ax._stale_viewlim_y
+                     for ax in self._shared_y_axes.get_siblings(self))
+        scalez = any(ax._stale_viewlim_z
+                     for ax in self._shared_z_axes.get_siblings(self))
+        if scalex or scaley or scalez:
+            for ax in self._shared_x_axes.get_siblings(self):
+                ax._stale_viewlim_x = False
+            for ax in self._shared_y_axes.get_siblings(self):
+                ax._stale_viewlim_y = False
+            for ax in self._shared_z_axes.get_siblings(self):
+                ax._stale_viewlim_z = False
+            self.autoscale_view(scalex=scalex, scaley=scaley, scalez=scalez)
+
     def unit_cube(self, vals=None):
         minx, maxx, miny, maxy, minz, maxz = vals or self.get_w_lims()
         return [(minx, miny, minz),
@@ -378,6 +397,8 @@ def apply_aspect(self, position=None):
 
     @artist.allow_rasterization
     def draw(self, renderer):
+        self._unstale_viewLim()
+
         # draw the background patch
         self.patch.draw(renderer)
         self._frameon = False
@@ -477,9 +498,9 @@ def _unit_change_handler(self, axis_name, event=None):
                 self._unit_change_handler, axis_name, event=object())
         _api.check_in_list(self._get_axis_map(), axis_name=axis_name)
         self.relim()
-        self.autoscale_view(scalex=(axis_name == "x"),
-                            scaley=(axis_name == "y"),
-                            scalez=(axis_name == "z"))
+        self._request_autoscale_view(scalex=(axis_name == "x"),
+                                     scaley=(axis_name == "y"),
+                                     scalez=(axis_name == "z"))
 
     def update_datalim(self, xys, **kwargs):
         pass
@@ -528,6 +549,24 @@ def set_autoscalez_on(self, b):
         """
         self._autoscaleZon = b
 
+    def set_xmargin(self, m):
+        # docstring inherited
+        scalez = self._stale_viewlim_z
+        super().set_xmargin(m)
+        # Superclass is 2D and will call _request_autoscale_view with defaults
+        # for unknown Axis, which would be scalez=True, but it shouldn't be for
+        # this call, so restore it.
+        self._stale_viewlim_z = scalez
+
+    def set_ymargin(self, m):
+        # docstring inherited
+        scalez = self._stale_viewlim_z
+        super().set_ymargin(m)
+        # Superclass is 2D and will call _request_autoscale_view with defaults
+        # for unknown Axis, which would be scalez=True, but it shouldn't be for
+        # this call, so restore it.
+        self._stale_viewlim_z = scalez
+
     def set_zmargin(self, m):
         """
         Set padding of Z data limits prior to autoscaling.
@@ -542,6 +581,7 @@ def set_zmargin(self, m):
         if m < 0 or m > 1:
             raise ValueError("margin must be in range 0 to 1")
         self._zmargin = m
+        self._request_autoscale_view(scalex=False, scaley=False, scalez=True)
         self.stale = True
 
     def margins(self, *margins, x=None, y=None, z=None, tight=True):
@@ -639,8 +679,8 @@ def autoscale(self, enable=True, axis='both', tight=None):
                 self._autoscaleZon = scalez = bool(enable)
             else:
                 scalez = False
-        self.autoscale_view(tight=tight, scalex=scalex, scaley=scaley,
-                            scalez=scalez)
+        self._request_autoscale_view(tight=tight, scalex=scalex, scaley=scaley,
+                                     scalez=scalez)
 
     def auto_scale_xyz(self, X, Y, Z=None, had_data=None):
         # This updates the bounding boxes as to keep a record as to what the
@@ -656,6 +696,19 @@ def auto_scale_xyz(self, X, Y, Z=None, had_data=None):
         # Let autoscale_view figure out how to use this data.
         self.autoscale_view()
 
+    # API could be better, right now this is just to match the old calls to
+    # autoscale_view() after each plotting method.
+    def _request_autoscale_view(self, tight=None, scalex=True, scaley=True,
+                                scalez=True):
+        if tight is not None:
+            self._tight = tight
+        if scalex:
+            self._stale_viewlim_x = True  # Else keep old state.
+        if scaley:
+            self._stale_viewlim_y = True
+        if scalez:
+            self._stale_viewlim_z = True
+
     def autoscale_view(self, tight=None, scalex=True, scaley=True,
                        scalez=True):
         """
@@ -766,6 +819,9 @@ def set_xlim3d(self, left=None, right=None, emit=True, auto=False,
         left, right = sorted([left, right], reverse=bool(reverse))
         self.xy_viewLim.intervalx = (left, right)
 
+        # Mark viewlims as no longer stale without triggering an autoscale.
+        for ax in self._shared_x_axes.get_siblings(self):
+            ax._stale_viewlim_x = False
         if auto is not None:
             self._autoscaleXon = bool(auto)
 
@@ -821,6 +877,9 @@ def set_ylim3d(self, bottom=None, top=None, emit=True, auto=False,
             bottom, top = top, bottom
         self.xy_viewLim.intervaly = (bottom, top)
 
+        # Mark viewlims as no longer stale without triggering an autoscale.
+        for ax in self._shared_y_axes.get_siblings(self):
+            ax._stale_viewlim_y = False
         if auto is not None:
             self._autoscaleYon = bool(auto)
 
@@ -876,6 +935,9 @@ def set_zlim3d(self, bottom=None, top=None, emit=True, auto=False,
             bottom, top = top, bottom
         self.zz_viewLim.intervalx = (bottom, top)
 
+        # Mark viewlims as no longer stale without triggering an autoscale.
+        for ax in self._shared_z_axes.get_siblings(self):
+            ax._stale_viewlim_z = False
         if auto is not None:
             self._autoscaleZon = bool(auto)
 
@@ -1346,7 +1408,8 @@ def locator_params(self, axis='both', tight=None, **kwargs):
             self.yaxis.get_major_locator().set_params(**kwargs)
         if _z:
             self.zaxis.get_major_locator().set_params(**kwargs)
-        self.autoscale_view(tight=tight, scalex=_x, scaley=_y, scalez=_z)
+        self._request_autoscale_view(tight=tight, scalex=_x, scaley=_y,
+                                     scalez=_z)
 
     def tick_params(self, axis='both', **kwargs):
         """

diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -895,6 +895,28 @@ def test_autoscale():
     assert ax.get_w_lims() == (0, 1, -.1, 1.1, -.4, 2.4)
 
 
+@pytest.mark.parametrize('axis', ('x', 'y', 'z'))
+@pytest.mark.parametrize('auto', (True, False, None))
+def test_unautoscale(axis, auto):
+    fig = plt.figure()
+    ax = fig.gca(projection='3d')
+
+    x = np.arange(100)
+    y = np.linspace(-0.1, 0.1, 100)
+    ax.scatter(x, y)
+
+    get_autoscale_on = getattr(ax, f'get_autoscale{axis}_on')
+    set_lim = getattr(ax, f'set_{axis}lim')
+    get_lim = getattr(ax, f'get_{axis}lim')
+
+    post_auto = get_autoscale_on() if auto is None else auto
+
+    set_lim((-0.5, 0.5), auto=auto)
+    assert post_auto == get_autoscale_on()
+    fig.canvas.draw()
+    np.testing.assert_array_equal(get_lim(), (-0.5, 0.5))
+
+
 @mpl3d_image_comparison(['axes3d_ortho.png'], remove_text=False)
 def test_axes3d_ortho():
     fig = plt.figure()