{,Range}Slider: accept callable valfmt arguments

[doronbehar]

PR summary

• Why is this change necessary? What problem does it solve?

I wanted to create a slider for an "order of magnitude" parameter, that scales logarithmic, but prints concisely the number in the valfmt parameter.

• What is the reasoning for this implementation?

Somewhat based on the idea here:

• Support callable for formatting of Sankey labels #19187

Example:

from matplotlib.widgets import Slider
import matplotlib.pyplot as plt

fig, ax=plt.subplots()

s = Slider(
    ax=ax,
    label=r"$\mathcal{O}(x)$",
    valmin=0,
    valmax=1,
    #valfmt=lambda x: f"$10^{{{x:.1f}}}$",
    valfmt=lambda x: f"{(10**x):.0f}"
)
s.on_changed(lambda x: print(10**x))
plt.show()

I'd like to get feedback before writing examples to documentation.

PR checklist

• new and changed code is tested
• Update docstrings of Slider & RangeSlider classes.
• Plotting related features are demonstrated in an example
• New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines

[timhoffm]

This is fundamentally reasonable. I would make the range callable two parameters rather than a sequence.

[doronbehar]

This is fundamentally reasonable. I would make the range callable two parameters rather than a sequence.

Done! But it will take me a day to reach the docs updating and release notes etc.

[doronbehar]

Converted to a draft to reflect that.

[doronbehar]

All docs related changes needed are ready for review.

[doronbehar]

Indeed my phrasings aren't always concise :) It's OK. Thanks for the review, fixed them all.

[doronbehar]

Done :).