Move Line2D units handling to Axes & deprecate "units finalize" signal.

anntzer · anntzer · commit aa4b36c740a9 · 2021-04-04T00:56:26.000+02:00
... rather than having each Line2D instance connect its own
callback.  (If we imagine a future where other artist classes can
also update themselves to use new units, one can imagine simply
having an `update_units` method on all artists (currently named
`recache_always`)).

I believe that the `units` and `units finalize` signals both
existed only to ensure that Line2D.recache_always was called before
`Axes._unit_change_handler`, but that's not necessary anymore (perhaps
we need a generic way of manipulating callback order but that'd be a
separate story).  Deprecating the signal directly on CallbackRegistry is
a bit ugly but that's how it was done for idle_event too...
diff --git a/doc/api/next_api_changes/deprecations/19858-AL.rst b/doc/api/next_api_changes/deprecations/19858-AL.rst
@@ -0,0 +1,4 @@
+"units finalize" signal
+~~~~~~~~~~~~~~~~~~~~~~~
+This signal (previously emitted by Axis instances) is deprecated.  Connect to
+"units" instead.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -652,7 +652,7 @@ def __init__(self, fig, rect,
         for name, axis in self._get_axis_map().items():
             axis.callbacks._pickled_cids.add(
                 axis.callbacks.connect(
-                    'units finalize', self._unit_change_handler(name)))
+                    'units', self._unit_change_handler(name)))
 
         rcParams = mpl.rcParams
         self.tick_params(
@@ -2402,6 +2402,8 @@ def _unit_change_handler(self, axis_name, event=None):
             return functools.partial(
                 self._unit_change_handler, axis_name, event=object())
         _api.check_in_list(self._get_axis_map(), axis_name=axis_name)
+        for line in self.lines:
+            line.recache_always()
         self.relim()
         self._request_autoscale_view(scalex=(axis_name == "x"),
                                      scaley=(axis_name == "y"))
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -201,6 +201,9 @@ def __setstate__(self, state):
     @_api.rename_parameter("3.4", "s", "signal")
     def connect(self, signal, func):
         """Register *func* to be called when signal *signal* is generated."""
+        if signal == "units finalize":
+            _api.warn_deprecated(
+                "3.5", name=signal, obj_type="signal", alternative="units")
         self._func_cid_map.setdefault(signal, {})
         proxy = _weak_or_strong_ref(func, self._remove_proxy)
         if proxy in self._func_cid_map[signal]:
diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -628,15 +628,6 @@ def get_window_extent(self, renderer):
             bbox = bbox.padded(ms)
         return bbox
 
-    @Artist.axes.setter
-    def axes(self, ax):
-        # call the set method from the base-class property
-        Artist.axes.fset(self, ax)
-        if ax is not None:
-            for axis in ax._get_axis_map().values():
-                axis.callbacks._pickled_cids.add(
-                    axis.callbacks.connect('units', self.recache_always))
-
     def set_data(self, *args):
         """
         Set the x and y data.
