matplotlib · Wojciech-Lange · Dec 21, 2018 · Dec 21, 2018 · Dec 21, 2018 · Feb 14, 2019
diff --git a/examples/text_labels_and_annotations/legend.py b/examples/text_labels_and_annotations/legend.py
@@ -21,8 +21,17 @@
 ax.plot(a, d, 'k:', label='Data length')
 ax.plot(a, c + d, 'k', label='Total message length')
 
+#Creates an arrow with pre-defined label.
+ax.annotate("",
+            xy=(1.5, 4.5), xytext=(1.5, 9.0),
+            arrowprops={'arrowstyle': '<->', 'color': 'C7'}, label='distance')
+
+
 legend = ax.legend(loc='upper center', shadow=True, fontsize='x-large')
 
+ax.annotate("", xy=(1.5, 4.5), xytext=(1.5, 9.0),
+            arrowprops={'arrowstyle': '<->', 'color': 'C7'}, label='distance')
+
 # Put a nicer background color on the legend.
 legend.get_frame().set_facecolor('C0')
 

diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -34,7 +34,7 @@
 from matplotlib.font_manager import FontProperties
 from matplotlib.lines import Line2D
 from matplotlib.patches import (Patch, Rectangle, Shadow, FancyBboxPatch,
-                                StepPatch)
+                                FancyArrowPatch, StepPatch)
 from matplotlib.collections import (LineCollection, RegularPolyCollection,
                                     CircleCollection, PathCollection,
                                     PolyCollection)
@@ -45,6 +45,7 @@
 from matplotlib.offsetbox import DraggableOffsetBox
 
 from matplotlib.container import ErrorbarContainer, BarContainer, StemContainer
+from matplotlib.text import Annotation
 from . import legend_handler
 
 
@@ -632,8 +633,10 @@ def draw(self, renderer):
             update_func=legend_handler.update_from_first_child),
         tuple: legend_handler.HandlerTuple(),
         PathCollection: legend_handler.HandlerPathCollection(),
-        PolyCollection: legend_handler.HandlerPolyCollection()
-        }
+        PolyCollection: legend_handler.HandlerPolyCollection(),
+        FancyArrowPatch: legend_handler.HandlerFancyArrowPatch(),
+    Annotation: legend_handler.HandlerAnnotation()
+    }
 
     # (get|set|update)_default_handler_maps are public interfaces to
     # modify the default handler map.
@@ -809,6 +812,7 @@ def _init_legend_box(self, handles, labels, markerfirst=True):
                                    children=[self._legend_title_box,
                                              self._legend_handle_box])
         self._legend_box.set_figure(self.figure)
+        self._legend_box.set_offset(self._findoffset)
         self.texts = text_list
         self.legendHandles = handle_list
 
@@ -1115,12 +1119,14 @@ def _get_legend_handles(axs, legend_handler_map=None):
     handles_original = []
     for ax in axs:
         handles_original += (ax.lines + ax.patches +
-                             ax.collections + ax.containers)
+                             ax.collections + ax.containers + ax.texts)
+
         # support parasite axes:
         if hasattr(ax, 'parasites'):
             for axx in ax.parasites:
                 handles_original += (axx.lines + axx.patches +
-                                     axx.collections + axx.containers)
+                                     axx.collections + axx.containers
+                                        + axx.texts)
 
     handler_map = Legend.get_default_handler_map()
 

diff --git a/lib/matplotlib/legend_handler.py b/lib/matplotlib/legend_handler.py
@@ -29,7 +29,7 @@ def legend_artist(self, legend, orig_handle, fontsize, handlebox)
 
 from matplotlib import cbook
 from matplotlib.lines import Line2D
-from matplotlib.patches import Rectangle
+from matplotlib.patches import Rectangle, FancyArrowPatch
 import matplotlib.collections as mcoll
 import matplotlib.colors as mcolors
 
@@ -768,3 +768,56 @@ def create_artists(self, legend, orig_handle,
         self.update_prop(p, orig_handle, legend)
         p.set_transform(trans)
         return [p]
+
+
+class HandlerFancyArrowPatch(HandlerPatch):
+    """
+    Handler for FancyArrowPatch instances.
+    """
+    def _create_patch(self, legend, orig_handle, xdescent, ydescent, width,
+                            height, fontsize):
+        arrow = FancyArrowPatch([-xdescent,
+                                    -ydescent + height / 2],
+                                    [-xdescent + width,
+                                     -ydescent + height / 2],
+                                    mutation_scale=width / 3)
+        arrow.set_arrowstyle(orig_handle.get_arrowstyle())
+        return arrow
+
+
+class HandlerAnnotation(HandlerBase):
+    """
+    Handler for Annotation instances.
+    Defers to HandlerFancyArrowPatch to draw the annotation arrow (if any).
+    Parameters
+    ----------
+    pad : float, optional
+    If None, fall back to `legend.borderpad` asstr the default.
+    In units of fraction of font size.
+    Default is None.
+    width_ratios : tuple, optional
+    The relative width of the respective text/arrow legend annotation pair.
+    Must be of length 2.
+    Default is [1,4].
+    """
+    def __init__(self, pad=None, width_ratios=[1, 4], **kwargs):
+
+        self._pad = pad
+        self._width_ratios = width_ratios
+
+        HandlerBase.__init__(self, **kwargs)
+
+    def create_artists(self, legend, orig_handle, xdescent,
+                           ydescent, width, height, fontsize,
+                           trans):
+
+        if orig_handle.arrow_patch is not None:
+
+            # Arrow without text
+
+            handler = HandlerFancyArrowPatch()
+            handle = orig_handle.arrow_patch
+
+        return handler.create_artists(legend, handle, xdescent,
+                                      ydescent, width, height,
+                                      fontsize, trans)