Restore autolimits status when pressing "home" key.

When pressing the "home" key, the autoscaling state should be
restored as well, as interactive zoom/pan could have turned it off.
test_toolbar_home_restores_autoscale shows an example of why.  Assume
one starts with `plot(range(11), range(11))`.  In linear scale this
autoscales to (0, 10) (assuming no margins or the old round limits
mode); in log scale this autoscales to (1, 10) (dropping the zero).  But
previously, when "home" did not restore autoscale state, then a manual
zoom followed by "home" (in linear scale) would set the limits to (0,
10) and turn off autoscale, after which switching to log scale
interactively would give incorrect autolimits.

Author: anntzer

lib/matplotlib/axes/_base.py

@@ -3985,35 +3985,30 @@ def _get_view(self):
         """
         Save information required to reproduce the current view.
 
-        Called before a view is changed, such as during a pan or zoom
-        initiated by the user. You may return any information you deem
-        necessary to describe the view.
+        This method is called before a view is changed, such as during a pan or zoom
+        initiated by the user.  It returns an opaque object that describes the current
+        view, in a format compatible with :meth:`_set_view`.
 
-        .. note::
-
-            Intended to be overridden by new projection types, but if not, the
-            default implementation saves the view limits. You *must* implement
-            :meth:`_set_view` if you implement this method.
+        The default implementation saves the view limits and autoscaling state.
+        Subclasses may override this as needed, as long as :meth:`_set_view` is also
+        adjusted accordingly.
         """
-        xmin, xmax = self.get_xlim()
-        ymin, ymax = self.get_ylim()
-        return xmin, xmax, ymin, ymax
+        return {
+            "xlim": self.get_xlim(), "autoscalex_on": self.get_autoscalex_on(),
+            "ylim": self.get_ylim(), "autoscaley_on": self.get_autoscaley_on(),
+        }
 
     def _set_view(self, view):
         """
         Apply a previously saved view.
 
-        Called when restoring a view, such as with the navigation buttons.
+        This method is called when restoring a view (with the return value of
+        :meth:`_get_view` as argument), such as with the navigation buttons.
 
-        .. note::
-
-            Intended to be overridden by new projection types, but if not, the
-            default implementation restores the view limits. You *must*
-            implement :meth:`_get_view` if you implement this method.
+        Subclasses that override :meth:`_get_view` also need to override this method
+        accordingly.
         """
-        xmin, xmax, ymin, ymax = view
-        self.set_xlim((xmin, xmax))
-        self.set_ylim((ymin, ymax))
+        self.set(**view)
 
     def _prepare_view_from_bbox(self, bbox, direction='in',
                                 mode=None, twinx=False, twiny=False):

lib/matplotlib/tests/test_backend_bases.py

@@ -280,6 +280,36 @@ def test_toolbar_zoompan():
     assert ax.get_navigate_mode() == "PAN"
 
 
+def test_toolbar_home_restores_autoscale():
+    fig, ax = plt.subplots()
+    ax.plot(range(11), range(11))
+
+    tb = NavigationToolbar2(fig.canvas)
+    tb.zoom()
+
+    # Switch to log.
+    KeyEvent("key_press_event", fig.canvas, "k", 100, 100)._process()
+    KeyEvent("key_press_event", fig.canvas, "l", 100, 100)._process()
+    assert ax.get_xlim() == ax.get_ylim() == (1, 10)  # Autolimits excluding 0.
+    # Switch back to linear.
+    KeyEvent("key_press_event", fig.canvas, "k", 100, 100)._process()
+    KeyEvent("key_press_event", fig.canvas, "l", 100, 100)._process()
+    assert ax.get_xlim() == ax.get_ylim() == (0, 10)  # Autolimits.
+
+    # Zoom in from (x, y) = (2, 2) to (5, 5).
+    start, stop = ax.transData.transform([(2, 2), (5, 5)])
+    MouseEvent("button_press_event", fig.canvas, *start, MouseButton.LEFT)._process()
+    MouseEvent("button_release_event", fig.canvas, *stop, MouseButton.LEFT)._process()
+    # Go back to home.
+    KeyEvent("key_press_event", fig.canvas, "h")._process()
+
+    assert ax.get_xlim() == ax.get_ylim() == (0, 10)
+    # Switch to log.
+    KeyEvent("key_press_event", fig.canvas, "k", 100, 100)._process()
+    KeyEvent("key_press_event", fig.canvas, "l", 100, 100)._process()
+    assert ax.get_xlim() == ax.get_ylim() == (1, 10)  # Autolimits excluding 0.
+
+
 @pytest.mark.parametrize(
     "backend", ['svg', 'ps', 'pdf',
                 pytest.param('pgf', marks=needs_pgf_xelatex)]

lib/mpl_toolkits/mplot3d/axes3d.py

@@ -1000,13 +1000,16 @@ def _button_release(self, event):
 
     def _get_view(self):
         # docstring inherited
-        return (self.get_xlim(), self.get_ylim(), self.get_zlim(),
-                self.elev, self.azim, self.roll)
+        return {
+            "xlim": self.get_xlim(), "autoscalex_on": self.get_autoscalex_on(),
+            "ylim": self.get_ylim(), "autoscaley_on": self.get_autoscaley_on(),
+            "zlim": self.get_zlim(), "autoscalez_on": self.get_autoscalez_on(),
+        }, (self.elev, self.azim, self.roll)
 
     def _set_view(self, view):
         # docstring inherited
-        xlim, ylim, zlim, elev, azim, roll = view
-        self.set(xlim=xlim, ylim=ylim, zlim=zlim)
+        props, (elev, azim, roll) = view
+        self.set(**props)
         self.elev = elev
         self.azim = azim
         self.roll = roll