Add a unique number to any renderer hash keys.

QuLogic · QuLogic · commit 7a49d2085f3d · 2017-06-03T02:22:33.000-04:00
The result of id() is only guaranteed to be unique for objects that
exist at the same time. This global integer is a quick and light way to
ensure that new renderers that match an old one don't produce the same
caching key.
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
@@ -0,0 +1,11 @@
+Unique identifier added to `RendererBase` classes
+`````````````````````````````````````````````````
+
+Since ``id()`` is not guaranteed to be unique between objects that exist at
+different times, a new private property ``_uid`` has been added to
+`RendererBase` which is used along with the renderer's ``id()`` to cache
+certain expensive operations.
+
+If a custom renderer does not subclass `RendererBase` or `MixedModeRenderer`,
+it is not required to implement this ``_uid`` property, but this may produce
+incorrect behavior when the renderers' ``id()`` clashes.
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -100,6 +100,11 @@
 }
 
 
+# Used to ensure that caching based on renderer id() is unique without being as
+# expensive as a real UUID.
+_unique_renderer_id = 0
+
+
 def register_backend(format, backend, description=None):
     """
     Register a backend for saving to a given file format.
@@ -212,10 +217,25 @@ class RendererBase(object):
 
     """
     def __init__(self):
+        self._id = None
         self._texmanager = None
 
         self._text2path = textpath.TextToPath()
 
+    @property
+    def _uid(self):
+        """
+        A lightweight id for unique-ification purposes.
+
+        Along with id(self), this combination should be unique enough to use as
+        part of a caching key.
+        """
+        if self._id is None:
+            global _unique_renderer_id
+            _unique_renderer_id += 1
+            self._id = _unique_renderer_id
+        return self._id
+
     def open_group(self, s, gid=None):
         """
         Open a grouping element with label *s*. If *gid* is given, use
diff --git a/lib/matplotlib/backends/backend_mixed.py b/lib/matplotlib/backends/backend_mixed.py
@@ -49,6 +49,7 @@ def __init__(self, figure, width, height, dpi, vector_renderer,
         if raster_renderer_class is None:
             raster_renderer_class = RendererAgg
 
+        self._id = None
         self._raster_renderer_class = raster_renderer_class
         self._width = width
         self._height = height
@@ -80,6 +81,18 @@ def __init__(self, figure, width, height, dpi, vector_renderer,
         _text2path _get_text_path_transform height width
         """.split()
 
+    @property
+    def _uid(self):
+        """
+        See matplotlib.backend_bases.RendererBase._uid.
+        """
+        if self._id is None:
+            from matplotlib import backend_bases
+            backend_bases._unique_renderer_id
+            backend_bases._unique_renderer_id += 1
+            self._id = backend_bases._unique_renderer_id
+        return self._id
+
     def _set_current_renderer(self, renderer):
         self._renderer = renderer
 
diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -907,11 +907,12 @@ def get_prop_tup(self, renderer=None):
         need to know if the text has changed.
         """
         x, y = self.get_unitless_position()
+        renderer = renderer or self._renderer
         return (x, y, self.get_text(), self._color,
                 self._verticalalignment, self._horizontalalignment,
                 hash(self._fontproperties),
                 self._rotation, self._rotation_mode,
-                self.figure.dpi, id(renderer or self._renderer),
+                self.figure.dpi, id(renderer), getattr(renderer, '_uid', 0),
                 self._linespacing
                 )
 
