PR summary

When creating an annotation using boxed text in an arrow shape (patches.BoxStyle.LArrow/RArrow/DArrow), head_width and head_angle arguments may now be passed to adjust the size of the arrow head(s), and (via the use of negative angles) generate 'reversed' arrow heads. Addresses #24618 and is a direct continuation of @Abitamim's work in #24744.

This solves both the issue initially mentioned in #24618 (creating a pentagonal 'road-sign' annotation box), as well as allowing for many other customisation options for arrows; for example, a reversed-head DArrow could act as a way to bring attention to a certain region on an axis.

import matplotlib.pyplot as plt

fig, ax = plt.subplots(figsize=(4, 3))

t1 = ax.text(0.5, 0.75, "Road-sign",
            ha="center", va="center", size=15,
            bbox=dict(boxstyle="rarrow,pad=0.3,head_width=1,head_angle=45",
                      fc="lightblue", ec="steelblue", lw=2))

t2 = ax.text(0.5, 0.25, "  Reversed heads   ",
            ha="center", va="center", size=15,
            bbox=dict(boxstyle="darrow,pad=0.3,head_width=1.5,head_angle=-45",
                      fc="lightblue", ec="steelblue", lw=2))

plt.show()

A new test, test_boxarrow_adjustment, has been added to test these options.

PR checklist

• "closes [ENH]: "Road sign" boxstyle/annotation #24618" is in the body of the PR description to link the related issue
• new and changed code is tested
• 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