Draw connections between the same objects as arcs

[astoeckel]

Previously, connections between the same objects were drawn on top of each other. This patch draws connections between the same objects as arcs of different radii, making it possible to distinguish them visually.

This is of primary interest when having separate excitatory/inhibitory connections.

Note that connections from/to networks are still drawn as a single line. This is controlled by the has_arcs variable in Connection.redraw().

Here is the code I used for testing:

import nengo
import numpy as np

model = nengo.Network()
with model:
    stim = nengo.Node([0])
    a = nengo.Ensemble(n_neurons=50, dimensions=1)
    b = nengo.Ensemble(n_neurons=50, dimensions=1)
    c = nengo.Ensemble(n_neurons=50, dimensions=1)

    with nengo.Network() as net1:
        d = nengo.Ensemble(n_neurons=50, dimensions=1)
        e = nengo.Ensemble(n_neurons=50, dimensions=1)
        nengo.Connection(d, e)
        nengo.Connection(d, e)
        nengo.Connection(d, e)

    with nengo.Network() as net2:
        f = nengo.Ensemble(n_neurons=50, dimensions=1)
        g = nengo.Ensemble(n_neurons=50, dimensions=1)
        nengo.Connection(f, g)
        nengo.Connection(f, g)

    nengo.Connection(stim, a)
    nengo.Connection(stim, a.neurons, transform=-np.ones((50, 1)))
    nengo.Connection(stim, b)
    nengo.Connection(stim, c)

    nengo.Connection(a, d)
    nengo.Connection(a, e)
    nengo.Connection(d, e)
    nengo.Connection(d, f)

    nengo.Connection(b, c)
    nengo.Connection(c, b.neurons, transform=-100*np.ones((50, 1)))

[tcstewar]

This is awesome! Definitely a big improvement, and having this display would have helped me catch a bug or two in the past.

It's now merged. Thank you!