LineCollection.contains (ab)uses pickradius<=0 as marker for "filled"

[anntzer]

Bug report

Bug summary

When the pickradius of a LineCollection is set to a <=0 value, LineCollection.contains treats the polygon as "closed".

Code for reproduction

from matplotlib import pyplot as plt
from matplotlib.collections import LineCollection
from matplotlib.backend_bases import MouseEvent
import numpy as np

fig, axs = plt.subplots(2)

for ax, pr in zip(axs, [0, 10]):
    coll = LineCollection([[(0, 0), (1, 0), (0, 1)]])
    ax.add_collection(coll)
    ax.set(xlim=(-1, 2), ylim=(-1, 2))
    coll.set_pickradius(pr)
    for x in np.linspace(*ax.get_xlim())[1:-1]:
        for y in np.linspace(*ax.get_ylim())[1:-1]:
            x1, y1 = ax.transData.transform((x, y))
            contained, _ = coll.contains(
                MouseEvent("button_press_event", fig.canvas, x1, y1))
            ax.plot(x, y, "o", c="g" if contained else "r", ms=1)

plt.show()

Actual outcome

Note how on the top LineCollection (using pickradius=0), all points "in" the closed polygon are considered "contained".

Expected outcome

Only points exactly on the LineCollection are contained for pickradius = 0, no points are contained for pickradius < 0 (consistently with Line2D).

---

The relevant code is in Line2D.contains:

        ind = _path.point_in_path_collection(
            mouseevent.x, mouseevent.y, pickradius,
            transform.frozen(), paths, self.get_transforms(),
            offsets, transOffset, pickradius <= 0,  # <--- this last argument is "filled"
            self._offset_position)

Matplotlib version

• Operating system: linux
• Matplotlib version: master, likely since a long time ago
• Matplotlib backend (print(matplotlib.get_backend())): any
• Python version: 38
• Jupyter version (if applicable): no
• Other libraries: no

[github-actions]

This issue has been marked "inactive" because it has been 365 days since the last comment. If this issue is still present in recent Matplotlib releases, or the feature request is still wanted, please leave a comment and this label will be removed. If there are no updates in another 30 days, this issue will be automatically closed, but you are free to re-open or create a new issue if needed. We value issue reports, and this procedure is meant to help us resurface and prioritize issues that have not been addressed yet, not make them disappear. Thanks for your help!