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matplotlib · tacaswell · Jan 28, 2014 · Sep 6, 2013 · Jan 27, 2014 · Jan 28, 2014
commit 59e7d13c9e2d80ca82ae123fac2de2eba636eb9e
diff --git a/doc/api/api_changes.rst b/doc/api/api_changes.rst
@@ -75,7 +75,8 @@ original location:
  `matplotlib.patches.Polygon` object.

 * The legend handler interface has changed from a callable, to any object
-  which implements the ``legend_artists`` method. See
+  which implements the ``legend_artists`` method (a deprecation phase will
+  see this interface be maintained for v1.4). See
  :ref:`plotting-guide-legend` for further details. Further legend changes
  include:


diff --git a/doc/users/legend_guide.rst b/doc/users/legend_guide.rst
@@ -42,23 +42,27 @@ handles and their associated labels. This functionality is equivalent to::

 The :meth:`~matplotlib.axes.Axes.get_legend_handles_labels` function returns
 a list of handles/artists which exist on the Axes which can be used to
-generate entries for the resulting legend.
+generate entries for the resulting legend - it is worth noting however that
+not all artists can be added to a legend, at which point a "proxy" will have
+to be created (see :ref:`proxy_legend_handles` for further details).

 For full control of what is being added to the legend, it is common to pass
 the appropriate handles directly to :func:`legend`::

-    line2, = plt.plot([1,2,3], label='Line 2')
-    line1, = plt.plot([3,2,1], label='Line 1')
-    plt.legend(handles=[line1, line2])
+    line_up, = plt.plot([1,2,3], label='Line 2')
+    line_down, = plt.plot([3,2,1], label='Line 1')
+    plt.legend(handles=[line_up, line_down])

 In some cases, it is not possible to set the label of the handle, so it is
 possible to pass through the list of labels to :func:`legend`::

-    line2, = plt.plot([1,2,3], label='Line 2')
-    line1, = plt.plot([3,2,1], label='Line 1')
-    plt.legend([line1, line2], ['Custom label for line 1', 'Line 1'])
+    line_up, = plt.plot([1,2,3], label='Line 2')
+    line_down, = plt.plot([3,2,1], label='Line 1')
+    plt.legend([line_up, line_down], ['Line Up', 'Line Down'])


+.. _proxy_legend_handles:
+
 Creating artists specifically for adding to the legend (aka. Proxy artists)
 ===========================================================================


diff --git a/lib/matplotlib/backends/__init__.py b/lib/matplotlib/backends/__init__.py
@@ -10,7 +10,8 @@
 # ipython relies on interactive_bk being defined here
 from matplotlib.rcsetup import interactive_bk

-__all__ = ['backend']
+__all__ = ['backend','show','draw_if_interactive',
+           'new_figure_manager', 'backend_version']

 backend = matplotlib.get_backend() # validates, to match all_backends


diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -33,7 +33,8 @@

 from matplotlib import rcParams
 from matplotlib.artist import Artist, allow_rasterization
-from matplotlib.cbook import is_string_like, iterable, silent_list, safezip
+from matplotlib.cbook import (is_string_like, iterable, silent_list, safezip,
+                              warn_deprecated)
 from matplotlib.font_manager import FontProperties
 from matplotlib.lines import Line2D
 from matplotlib.patches import Patch, Rectangle, Shadow, FancyBboxPatch
@@ -621,6 +622,18 @@ def _init_legend_box(self, handles, labels):
                                        height=height,
                                        xdescent=0., ydescent=descent)
                handleboxes.append(handlebox)
+
+                # Deprecate the old behaviour of accepting callable
+                # legend handlers in favour of the "legend_artist"
+                # interface.
+                if (not hasattr(handler, 'legend_artist') and
+                        callable(handler)):
+                    handler.legend_artist = handler.__call__
+                    warn_deprecated('1.4',
+                                    ('Legend handers must now implement a '
+                                     '"legend_artist" method rather than '
+                                     'being a callable.'))
+
                # Create the artist for the legend which represents the
                # original artist/handle.
                handle_list.append(handler.legend_artist(self, orig_handle,

diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -9,8 +9,10 @@
 import numpy as np

 from matplotlib.testing.decorators import image_comparison, cleanup
+from matplotlib.cbook import MatplotlibDeprecationWarning
 import matplotlib.pyplot as plt
 import matplotlib as mpl
+import matplotlib.patches as mpatches


 @image_comparison(baseline_images=['legend_auto1'], remove_text=True)
@@ -130,6 +132,33 @@ def test_legend_label_loc_args(self):
        deprecation.assert_called_with('1.4', self.deprecation_message)
        Legend.assert_called_with(plt.gca(), [], ['hello world'], loc=1)

+    @cleanup
+    def test_old_legend_handler_interface(self):
+        # Check the deprecated warning is created and that the appropriate
+        # call to the legend handler is made.
+        class AnyObject(object):
+            pass
+
+        class AnyObjectHandler(object):
+            def __call__(self, legend, orig_handle, fontsize, handlebox):
+                x0, y0 = handlebox.xdescent, handlebox.ydescent
+                width, height = handlebox.width, handlebox.height
+                patch = mpatches.Rectangle([x0, y0], width, height, facecolor='red',
+                                           edgecolor='black', hatch='xx', lw=3,
+                                           transform=handlebox.get_transform())
+                handlebox.add_artist(patch)
+                return patch
+
+        with mock.patch('warnings.warn') as warn:
+            plt.legend([None], ['My first handler'],
+                       handler_map={None: AnyObjectHandler()})
+
+        warn.assert_called_with(u'Legend handers must now implement a '
+                                 '"legend_artist" method rather than '
+                                 'being a callable.',
+                                MatplotlibDeprecationWarning,
+                                stacklevel=1)
+
    @cleanup
    def test_legend_handle_label_loc_args(self):
        # Check the deprecated warning is created and that the appropriate