Add capstyle and joinstyle attributes to Collection class (Issue #8277) by simonpf · Pull Request #9523 · matplotlib/matplotlib

simonpf · 2017-10-22T17:21:58Z

PR Summary

Adds _capstyle and _joinstyle attributes as well as corresponding setters to Collection class. Changes draw class method to set capstyle and joinstyle of renderer accordingly. This solves the problem of not being able to set capstyle and joinstyle of LineCollection (Issue #8277).

PR Checklist

Has Pytest style unit tests
Code is PEP 8 compliant
New features are documented, with examples if plot related
Documentation is sphinx and numpydoc compliant
Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

Example

import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection
from matplotlib import colors as mcolors

import numpy as np

x = np.arange(100)
ys = x[::10, np.newaxis] + (x + 10.0 * np.random.rand(*x.shape))[np.newaxis, :]

segs = np.zeros((10, 100, 2), float)
segs[:, :, 1] = ys
segs[:, :, 0] = x

segs = np.ma.masked_where((segs > 50) & (segs < 60), segs)
ax = plt.axes()
ax.set_xlim(x.min(), x.max())
ax.set_ylim(ys.min(), ys.max())

colors = [mcolors.to_rgba(c)
          for c in plt.rcParams['axes.prop_cycle'].by_key()['color']]
line_segments = LineCollection(segs, linewidths=(2, 3, 4, 5),
                               colors=colors, linestyle='solid')
line_segments.set_joinstyle("miter")
line_segments.set_capstyle("round")
ax.add_collection(line_segments)
ax.set_title('Line collection with masked arrays')
plt.show()

anntzer · 2017-10-22T18:08:28Z

Unless I am mistaken, this does not actually cause the capstyle and joinstyle to be used while drawing. You probably need to update Collection.draw accordingly.

Note that unless you mess with Renderer.draw_path_collection, the capstyle and joinstyle will be global ones (not settable per-item). On the one hand, who wants to set these per item? On the other hand, even antialiasing is settable per-item.

simonpf · 2017-10-22T19:40:54Z

Hi @anntzer,

I did update change Collection.draw and tested this with the example given in the issue and the one above.

Yes, I was also wondering if it should be possible to set cap- and joinstyle for each element in the collection, but as I understand it, this is not the solution proposed in the issue.

anntzer · 2017-10-22T20:03:28Z

Sorry, I was not careful when proofreading. Indeed they are set correctly.

Allowing per-item setting is a much more complicated piece of work, so I think I'm OK with not having it for now.

I think this warrants an image test (to show that the styles are actually propagated to the draw), and a whatsnew entry.

NelleV

Thanks a lot for this patch! I have a few minor comments. I'm happy to create a PR on your branch or to push the changes directly to your branch if you prefer not fixing those.

NelleV · 2017-10-22T20:12:03Z

lib/matplotlib/collections.py

                 facecolors=None,
                 linewidths=None,
                 linestyles='solid',
+                 capstyle=None,


Those two new arguments need to be documented in the docstring for this class.

NelleV · 2017-10-22T20:12:46Z

lib/matplotlib/collections.py

+        """
+        Set the capstyle for the collection.
+
+        ACCEPTS: ['butt' | 'round' | 'projecting']


We're using numpydoc style docstring. Can you delete this line, but add this to the parameters list? (See comment bellow).

Until we actually get rid of the kwdoc mechanism (whether we do so is a separate issue), I would prefer leaving the ACCEPTS strings there, as it avoids having an ugly property -- unknown entry in the rendered table. (But that does not preclude documenting them in the parameters table below too -- I agree with @NelleV on that part.)

Same comment applies throughout.

NelleV · 2017-10-22T20:13:21Z

lib/matplotlib/collections.py

+
+        Parameters
+        ----------
+        cs : The capstyle


Considering we are using numpydoc, that should be:

cs : ['butt' | 'round' | 'projecting'] the capstyle

NelleV · 2017-10-22T20:14:19Z

lib/matplotlib/collections.py

+        """
+        Set the joinstyle for the collection.
+
+        ACCEPTS: ['miter' | 'round' | 'bevel']


Same here :)

NelleV · 2017-10-22T21:29:07Z

lib/matplotlib/collections.py

        * *facecolors*: None
        * *linewidths*: None
+        * *capstyle*:   None
+        * *joinstyle*:  None


simonpf · 2017-10-24T05:46:55Z

Sorry for the noise, I had some problems with my test setup and missed the PEP8 warnings.

simonpf · 2017-10-26T05:58:49Z

So is there anything left to do on this?

anntzer · 2017-10-26T06:06:41Z

doc/users/whats_new.rst

 Improvements
 ++++++++++++

+Add `capstyle` and `joinstyle` attributes to `Collection`


capstyle and joinstyle should use two backquotes on both sides (this is somewhat poorly documented at http://matplotlib.org/devdocs/devel/documenting_mpl.html#formatting but the idea is that single backquotes mean "a python object that has its own entry in the docs", which is the case for Collection but not for capstyle and joinstyle, which are just parameters).

Same below.

anntzer · 2017-10-26T06:09:19Z

lib/matplotlib/tests/test_collections.py

+
+@image_comparison(baseline_images=['capstyle'],
+                  extensions=['png'])
+def test_capstyle_image():


Can you join the two image comparisons into a single test and thus a single reference image? Reference test images are a large part of why the repo is so heavy, so we're trying to be careful with adding more of them.
After doing so, you can squash the old images out of the history with rebase; if you're not comfortable with it I can take care of it when merging too, just let me know.

anntzer · 2017-10-26T06:10:03Z

Just some minor stuff. The rest looks good.

simonpf · 2017-10-26T10:28:54Z

OK, fixed now.

anntzer

LGTM :-)

NelleV · 2017-10-26T17:24:18Z

Thanks for the contribution @simonpf !

tacaswell · 2017-10-30T01:09:27Z

doc/users/whats_new.rst

 Improvements
 ++++++++++++

+Add ``capstyle`` and ``joinstyle`` attributes to `Collection`


This got put into the 2.1 whats_new 😞

simonpf changed the title ~~Added capstyle and joinstyle attributes to Collection class (Issue #8277)~~ Add capstyle and joinstyle attributes to Collection class (Issue #8277) Oct 22, 2017

NelleV reviewed Oct 22, 2017

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lib/matplotlib/collections.py

* *facecolors*: None

* *linewidths*: None

* *capstyle*: None

* *joinstyle*: None

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👍

dstansby added this to the v2.2 milestone Oct 23, 2017

anntzer reviewed Oct 26, 2017

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simonpf added 4 commits October 26, 2017 09:59

Added capstyle and joinstyle attributes to Collection class.

baa5b59

Added test cases for setting of capstyle and joinstyle attributes.

e56e3ba

Added image test for capstyle and joinstyle of Collection class

8833778

Added whatsnew entry.

36b9c46

simonpf force-pushed the hacktoberfest branch from 8b22d5e to 36b9c46 Compare October 26, 2017 08:08

anntzer approved these changes Oct 26, 2017

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NelleV merged commit 3c3e8ba into matplotlib:master Oct 26, 2017

tacaswell reviewed Oct 30, 2017

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QuLogic mentioned this pull request Jan 10, 2018

Set line join/cap on geometry rendering SciTools/cartopy#999

Closed

QuLogic modified the milestones: needs sorting, v2.2.0 Feb 12, 2018

anntzer mentioned this pull request Sep 26, 2019

capstyle/joinstyle support for matplotlib.collections.Collection #8277

Closed

QuLogic mentioned this pull request May 4, 2023

Fix default return of Collection.get_{cap,join}style #25810

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PR Summary

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anntzer commented Oct 22, 2017

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simonpf commented Oct 22, 2017 •

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anntzer Oct 22, 2017 •

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