Annotation legend by jlecoeur · Pull Request #8292 · matplotlib/matplotlib · GitHub

Fixes #8236

I added new legend handlers for Text, FancyArrowPatch and Annotation artists (HandlerText, HandlerFancyArrowPatch and HandlerAnnotation).

HandlerAnnotation can draw different artists in the legend:

if the annotation has no text and no arrow, it draws a white Rectangle
if the annotation has only text, it uses HandlerText to draw a text. The text is replaced by 'Aa' if it is longer than one character. (This is configurable by setting rep_str and rep_maxlen.)
if the annotation has only an arrow, it uses HandlerFancyArrowPatch to draw an arrow
If the annotation has both text and arrow, it uses HandlerTuple to draw both.

In HandlerTuple, I added the possibility of different width ratios for the artists. HandlerAnnotation uses a width_ratios=[1,4] (ie. the arrow is 4 times wider than the text).

Example code:

import matplotlib
import matplotlib.pylab as plt
from matplotlib.patches import FancyArrowPatch
from matplotlib.legend_handler import HandlerAnnotation

fig, ax = plt.subplots(1)
ax.plot([0, 1], [0, 0], label='line1')
ax.plot([0, 1], [1, 1], label='line2')

# no text, no arrow
ax.annotate("",
            xy=(0.1,0.5),
            xytext=(0.1,0.5),
            label='annotation (empty)')

# text, no arrow
my_annotation = ax.annotate("X",
            xy=(0.1,0.5),
            xytext=(0.1,0.5),
            color='C2',
            label='annotation (text, no arrow)')

# no text, arrow
ax.annotate("",
            xy=(0.3,1.0),
            xytext=(0.3,0.0),
            arrowprops={'arrowstyle':'<->', 'color':'C7' },
            label='annotation (no text, arrow)')

# text, arrow
ax.annotate("Some long string",
            xy=(0.4,1.0),
            xytext=(0.35,0.1),
            arrowprops={'arrowstyle':'->', 'color':'C2' },
            color='C1',
            label='annotation (text + arrow)')

# Fancy arrow patch
arrpatch = FancyArrowPatch([0.5, 0.8], [0.9, 0.9],
                           arrowstyle='<|-',
                           mutation_scale=20,
                           color='C3',
                           label='arrowpatch')
ax.add_patch(arrpatch)

# Long text, will not be used in legend
ax.text(x=0.1, y=0.1,
        s='Hello',
        color='C5',
        label='text')

# Short text, copied in legend
ax.text(x=0.1, y=0.2,
        s='Z',
        color='C0',
        label='short text')

ax.legend(handler_map={my_annotation: HandlerAnnotation(rep_str='Abcde', rep_maxlen=0)})
fig.show()

output:

FancyArrowPatch <- Annotation?

fixed!

I forgot to ping you @bendichter @tacaswell

I am not sure what should be displayed when an annotation has no text and no arrow. I used a white Rectangle but this still looks awkward, would it be better (and possible?) to remove the legend entry in this case?

I wonder how useful it would be to make keyword arguments for the default replacement string for long text, and the maximal length of text entries (nice and clever names would have to be found…). The use case I could see is a user that would want to deviate from the default values (e.g. from "a" for strings longer than 1 char to "Aa" for strings longer than 2 chars) without having to override the whole create_artist method of HandlerText. To do things similar to what is shown here, i.e. (with dummy names for the kwargs)

plt.legend(handler_map={my_annotation: HandlerAnnotation(rep_str='Aa', str_maxlen=2)})

This looks beautiful! About the white rectangle, I can't think of a use case where you would have an annotation with no text and no arrow in the first place. I kind of liked having the white rectangle there because now I could imagine using it as a hack to give the legend subtitles.

@bendichter Ok! I made the rectangle transparent to make sure it is not visible even if something is below the legend

@afvincent Good point, I added these arguments and updated the example in the first comment. I also prefer 'Aa', which conveys the idea of 'some text' better than 'a' so I made it the default.

@jlecoeur Any update on this?

@tacaswell I would say it is done. Details like the relative size of character and arrow, or which character to use to represent long strings can be discussed, but the main thing is done and functional

"power cycled" to restart CI against current master.

@tacaswell Many Ci fails 👎 I do not have time to fix them at the moment, can you have a shot at it? Otherwise I will come back to it, but that would not be before a month from now.

Look forward to hearing from you in a month!

I'll take care of this for you!

Closing in lieu of the active, but not merged, #10688

Julien Lecoeur added 6 commits March 14, 2017 14:59

Add texts artists to legend

8b8b560

Allow different widths in legends handled by HandlerTuple

036daed

Add legend handler for FancyArrowPatch

d7bd069

Add legend handler for Text artists

70dd56d

Add legend handler for Annotation artists

b073527

Add Text, FancyArrowPatch and Annotation legend handlers to handler map

7b35e23

afvincent reviewed Mar 14, 2017

View reviewed changes

Fix typo and add documentation

240a497

afvincent added this to the 2.1 (next point release) milestone Mar 14, 2017

Julien Lecoeur added 6 commits March 15, 2017 10:00

Display transparent rectangle in legend for empty annotations

3e612e2

Add params in HandlerText: max string length and replacement string

f2de7f1

HandlerTuple: allow to pass a list of custom handlers

0c623ce

HandlerAnnotation: pass additionnal arguments to handle text correctly

aeed3e5

Shift Text legend artist laterally according to its length

db84d07

typo

f666224

tacaswell modified the milestones: 2.1 (next point release), 2.2 (next next feature release) Aug 29, 2017

tacaswell closed this Sep 24, 2017

tacaswell reopened this Sep 24, 2017

afvincent mentioned this pull request Oct 17, 2017

custom legends example #9451

Merged

magedhennawy mentioned this pull request Mar 5, 2018

Add legend handler and artist for FancyArrow #10688

Closed

magedhennawy pushed a commit to magedhennawy/matplotlib that referenced this pull request Mar 5, 2018

merged with matplotlib#8292

dd01695

jklymak closed this May 17, 2018

story645 removed this from the future releases milestone Oct 6, 2022

+              class HandlerAnnotation(HandlerBase):
+                  """
+                  Handler for FancyArrowPatch instances.

Annotation legend by jlecoeur · Pull Request #8292 · matplotlib/matplotlib · GitHub

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Annotation legend - #8292

Annotation legend#8292jlecoeur wants to merge 13 commits intomatplotlib:mastermatplotlib/matplotlib:masterfrom jlecoeur:annotation_legendjlecoeur/matplotlib:annotation_legendCopy head branch name to clipboard

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Annotation legend#8292
jlecoeur wants to merge 13 commits into
matplotlib:masterfrom
jlecoeur:annotation_legend

jlecoeur commented Mar 14, 2017 •
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