From a142ed0ef229888519ec272dc68321cc6cffc194 Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Thu, 21 Feb 2019 22:59:34 +0100
Subject: [PATCH] Allow sharing Locators and Formatters across Axises.

---
 lib/matplotlib/axis.py   | 43 ++++++++++++++++++++++++++++++++++++----
 lib/matplotlib/figure.py | 30 ++--------------------------
 2 files changed, 41 insertions(+), 32 deletions(-)

diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
index bfdb62df8377..b1571a948637 100644
--- a/lib/matplotlib/axis.py
+++ b/lib/matplotlib/axis.py
@@ -539,14 +539,20 @@ class Ticker:
     """
 
     def __init__(self):
+        self._axis = None
         self._locator = None
         self._formatter = None
         self._locator_is_default = True
         self._formatter_is_default = True
 
+    # The machinery below allows TickHelpers to be shared over multiple Axis.
+
     @property
     def locator(self):
-        return self._locator
+        locator = self._locator
+        if locator is not None:
+            locator.set_axis(self._axis)
+        return locator
 
     @locator.setter
     def locator(self, locator):
@@ -557,7 +563,10 @@ def locator(self, locator):
 
     @property
     def formatter(self):
-        return self._formatter
+        formatter = self._formatter
+        if formatter is not None:
+            formatter.set_axis(self._axis)
+        return formatter
 
     @formatter.setter
     def formatter(self, formatter):
@@ -566,6 +575,10 @@ def formatter(self, formatter):
                             'matplotlib.ticker.Formatter')
         self._formatter = formatter
 
+    @locator.setter
+    def locator(self, locator):
+        self._locator = locator
+
 
 class _LazyTickList:
     """
@@ -653,8 +666,8 @@ def __init__(self, axes, pickradius=15):
         self.isDefault_label = True
 
         self.axes = axes
-        self.major = Ticker()
-        self.minor = Ticker()
+        self._major = Ticker()
+        self._minor = Ticker()
         self.callbacks = cbook.CallbackRegistry()
 
         self._autolabelpos = True
@@ -680,6 +693,28 @@ def __init__(self, axes, pickradius=15):
         self.clear()
         self._set_scale('linear')
 
+    # The machinery below allows TickHelpers to be shared over multiple Axis.
+
+    @property
+    def major(self):
+        major = self._major
+        major._axis = self
+        return major
+
+    @major.setter
+    def major(self, major):
+        self._major = major
+
+    @property
+    def minor(self):
+        minor = self._minor
+        minor._axis = self
+        return minor
+
+    @minor.setter
+    def minor(self, minor):
+        self._minor = minor
+
     @property
     def isDefault_majloc(self):
         return self.major._locator_is_default
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
index aae1ef07a4ae..d2921532399f 100644
--- a/lib/matplotlib/figure.py
+++ b/lib/matplotlib/figure.py
@@ -902,38 +902,12 @@ def delaxes(self, ax):
         """
         Remove the `~.axes.Axes` *ax* from the figure; update the current Axes.
         """
-
-        def _reset_locators_and_formatters(axis):
-            # Set the formatters and locators to be associated with axis
-            # (where previously they may have been associated with another
-            # Axis instance)
-            axis.get_major_formatter().set_axis(axis)
-            axis.get_major_locator().set_axis(axis)
-            axis.get_minor_formatter().set_axis(axis)
-            axis.get_minor_locator().set_axis(axis)
-
-        def _break_share_link(ax, grouper):
-            siblings = grouper.get_siblings(ax)
-            if len(siblings) > 1:
-                grouper.remove(ax)
-                for last_ax in siblings:
-                    if ax is not last_ax:
-                        return last_ax
-            return None
-
         self._axstack.remove(ax)
         self._axobservers.process("_axes_change_event", self)
         self.stale = True
         self._localaxes.remove(ax)
-
-        # Break link between any shared axes
-        for name in ax._axis_names:
-            last_ax = _break_share_link(ax, ax._shared_axes[name])
-            if last_ax is not None:
-                _reset_locators_and_formatters(getattr(last_ax, f"{name}axis"))
-
-        # Break link between any twinned axes
-        _break_share_link(ax, ax._twinned_axes)
+        for axis_name in ax._shared_axes:
+            ax._shared_axes[axis_name].remove(ax)
 
     # Note: in the docstring below, the newlines in the examples after the
     # calls to legend() allow replacing it with figlegend() to generate the