set_position on Annotation is not working

[alefnula]

annotation.set_position(...) is not working in versions 1.2.1, 1.3.0 nor on the master.

Here is an example that demonstrates this.

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation

# Create initial data
data = np.array([[1,2,3,4,5], [7,4,9,2,3]])

# Create figure and axes
fig = plt.figure()
ax = plt.axes(xlim=(0, 20), ylim=(0, 20))

# Create initial objects
line, = ax.plot([], [], 'r-')
annotation = ax.annotate('A0', xy=(data[0][0], data[1][0]))
annotation.set_animated(True)

def init():
    return line, annotation

def update(num):
    newData = np.array([[1 + num, 2 + num / 2, 3, 4 - num / 4, 5 + num],
                        [7, 4, 9 + num / 3, 2, 3]])
    line.set_data(newData)
    # This is not working but in docs it is described as a setter
    # annotation.set_position((newData[0][0], newData[1][0]))
    # This works but this is described in docs as getter
    annotation.xytext = (newData[0][0], newData[1][0])
    return line, annotation

anim = animation.FuncAnimation(fig, update, frames=25, init_func=init,
                               interval=200, blit=True)
plt.show()

SO Question where the bug was discovered: Animate points with labels with mathplotlib

[mdboom]

I think the issue here is that set_position works only on raw text, not on an annotation. I think it's a matter of making the api more consistent between the two.

[tacaswell]

It looks like Annotation inherits from both Text and _AnnotationBase both of which maintain location information of the text. The set_position function updates the data structures used by the Text object. They look like they work, but that data is never used in Annotation.draw so it has no effect.

_AnnotationBase is also used as a baseclass for AnnotationBbox.

I would propose pulling xytext and xytextcoords out of _AnnotationBase and making keeping track of where the other end of the annotation is the job of sub-classes.

[tacaswell]

@alefnula I think this is fixed on master. Please check and if it is not we will reopen.