Replace use of renderer._uid by weakref.

anntzer · anntzer · commit 8d224089a855 · 2017-08-22T00:13:18.000-07:00
This avoids the need for a note regarding issues with renderer classes
that do not inherit from RendererBase.

Remember that the goal of _uid was to prevent two renderers from sharing
the same id() even though they were actually different (if one has been
GC'd and another is created at the same address).  Maintaining a weakref
to the renderer works as well, as weakref equality is thusly defined:

    If the referents are still alive, two references have the same
    equality relationship as their referents (regardless of the
    callback). If either referent has been deleted, the references are
    equal only if the reference objects are the same object.
diff --git a/doc/api/api_changes/2017-06-03-ES_unique_renderer.rst b/doc/api/api_changes/2017-06-03-ES_unique_renderer.rst
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -42,7 +42,6 @@
 from functools import partial
 import importlib
 import io
-import itertools
 import os
 import sys
 import time
@@ -101,12 +100,6 @@
 }
 
 
-# Used to ensure that caching based on renderer id() is unique without being as
-# expensive as a real UUID. 0 is used for renderers that don't derive from
-# here, so start at 1.
-_unique_renderer_id = itertools.count(1)
-
-
 def register_backend(format, backend, description=None):
     """
     Register a backend for saving to a given file format.
@@ -277,12 +270,7 @@ class RendererBase(object):
 
     """
     def __init__(self):
-        # A lightweight id for unique-ification purposes. Along with id(self),
-        # the combination should be unique enough to use as part of a cache key.
-        self._uid = next(_unique_renderer_id)
-
         self._texmanager = None
-
         self._text2path = textpath.TextToPath()
 
     def open_group(self, s, gid=None):
diff --git a/lib/matplotlib/backends/backend_mixed.py b/lib/matplotlib/backends/backend_mixed.py
@@ -5,7 +5,6 @@
 
 import six
 
-import matplotlib.backend_bases
 from matplotlib.backends.backend_agg import RendererAgg
 from matplotlib.tight_bbox import process_figure_for_rasterizing
 
@@ -50,9 +49,6 @@ def __init__(self, figure, width, height, dpi, vector_renderer,
         if raster_renderer_class is None:
             raster_renderer_class = RendererAgg
 
-        # See matplotlib.backend_bases.RendererBase._uid.
-        self._uid = next(matplotlib.backend_bases._unique_renderer_id)
-
         self._raster_renderer_class = raster_renderer_class
         self._width = width
         self._height = height
diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -9,6 +9,7 @@
 
 import math
 import warnings
+import weakref
 
 import contextlib
 
@@ -180,7 +181,6 @@ class Text(Artist):
     Handle storing and drawing of text in window or data coordinates.
     """
     zorder = 3
-
     _cached = maxdict(50)
 
     def __repr__(self):
@@ -912,7 +912,7 @@ def get_prop_tup(self, renderer=None):
                 self._verticalalignment, self._horizontalalignment,
                 hash(self._fontproperties),
                 self._rotation, self._rotation_mode,
-                self.figure.dpi, id(renderer), getattr(renderer, '_uid', 0),
+                self.figure.dpi, weakref.ref(renderer),
                 self._linespacing
                 )
 
