PR summary

This PR is to implement an SpanSelectorN, an implementation of multiples of theSpanSelector widget, which is very useful for spectroscopy and other sorts of normalisation processes used in data analysis. This is related to andcloses#28484.

This PR is currently in a draft state, as progress will be added to the implementation (testing, features, documentation etc).
A few bugs in current implementation, I have a fix somewhere on another drive will add soon.

MWE

import matplotlib.pyplot as pltfrom matplotlib.widgets import SpanSelectorNfig, ax = plt.subplots()ax.plot([1, 2, 3], [10, 50, 100])N=3def onSelectorGenerator(i):    def onselect(vmin, vmax):        print(f"Span {i}:\t", vmin, vmax)    return onselectfns = [onSelectorGenerator(i) for i in range(N)]span = SpanSelectorN(N, ax, fns, 'horizontal', useblit=True, interactive=True, drag_from_anywhere = True)plt.show()# Get all current positions....print(span.extends)

PR checklist

• "closes[ENH]: Add multiple span selector #28484" is in the body of the PR description tolink the related issue
• new and changed code istested
• Plotting related features are demonstrated in anexample
• New Features andAPI Changes are noted with adirective and release note
• Documentation complies withgeneral anddocstring guidelines