2D Arrow Widget

A draggable arrow overlay on a 2-D image panel. The tail sits at (x, y) and the head at (x + u, y + v) in data coordinates. Drag the body to move the whole arrow; drag the head handle to re-aim it (updating u / v). Add it with add_arrow_widget().

import numpy as np
import anyplotlib as apl

rng  = np.random.default_rng(3)
data = rng.standard_normal((128, 128)).cumsum(0).cumsum(1)
data = (data - data.min()) / (data.max() - data.min())
xy   = np.linspace(0, 10, 128)

fig, ax = apl.subplots(1, 1, figsize=(460, 460))
v = ax.imshow(data, axes=[xy, xy], units="nm")

arrow = v.add_arrow_widget(x=2.0, y=2.0, u=5.0, v=4.0,
                           color="#ff1744", linewidth=2)

fig

React to drags

Register a pointer_move handler to read the live geometry while the arrow is dragged or re-aimed (there is no on_changed method — the event system is the API). Read arrow.x/y/u/v inside the handler.

@arrow.add_event_handler("pointer_move")
def _report(event):
    print(f"tail=({arrow.x:.1f}, {arrow.y:.1f})  vector=({arrow.u:.1f}, {arrow.v:.1f})")


fig.set_help("Drag the arrow body to move it; drag the head to re-aim it.")

fig  # Interactive

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