Added rotation to the labels

[cvanelteren]

Hi,

Thanks for the nice package. I was missing the feature to manually control the angle of the label other than 0 degrees. This PR adds this feature as well as tidies up the code in labelline.py (i believe there is some unnecessary handling of properties going on). Sincerely, Casper

[cvanelteren]

Example:

code

```python import proplot as plt, numpy as np from labellines import labelLines x = np.linspace(0, 1) y = x fig, ax = plt.subplots() ax.plot(x, y, label="test") labelLines(ax.get_lines(), align=False, rotation=90) fig.show() plt.show(block=1) ```

[cphyc]

Thanks for the contribution! Unfortunately, it looks like some tests are failing. I tried locally, and your update broke the logic. The issue is that the get_rotation function is called whenever the axis size changes (e.g. when set_[xy]lim is called). In your current implementation, it is only called once as far as I could tell.

You can test this locally with the following script:

import matplotlib.pyplot as plt
import numpy as np

from labellines import labelLine

fig = plt.figure()
x = np.linspace(0, 10, 1000)
y = np.sin(x)

line, = plt.plot(x, y, label="$\sin(x)$")
labelLine(line, 2*np.pi, align=True)
plt.show()

Screencast from 2023-09-27 13-58-00.webm

Note that you can also run tests locally with pytest:

# Create a virtual environment
python -m venv venv
source venv/bin/activate
python -m pip install '.[test]'
python -m pytest --mpl --mpl-results-path=results --mpl-generate-summary=html

[cvanelteren]

Cool test setup! Didn't know pytest could export to html like this. The LabelLine object inherents from Text which has a default rotation implementation that should be compatible with this PR, what am I missing here? (see here for the implementation ).

EDIT: I am visually inspecting the failed tests but don't really see a difference by eye, e.g.

[cphyc]

Maybe try having a look at test_rotation_correction. From the test artefacts (https://github.com/cphyc/matplotlib-label-lines/actions/runs/6325489737?pr=161), I see this test as failing more obviously.

EDIT: I think your issue is that the rotation angle changes dynamically when the plot size changes. In your implementation _rotation is set at initialisation and doesn't change anymore.

[cphyc]

A bit more insight: your update breaks the piece of code that computes the rotation of the text to match the on-screen slope of the line. Since we're working in screen space, this depends on the size of the axis, which may have been updated since the LabelLines object got created.

So the _rotation property needs to be recomputed and cannot be cached (when we're using the auto_align keyword).

[cvanelteren]

Ah I see! I pushed a fix with some comments. The tests pass now.

[cphyc]

They do indeed! Let me review the PR now then.

[cvanelteren]

@cphyc I too hastily pushed the local commits. My bad! Current state should be good with changes to core as well. The default behavior is still aligning the labels with the curve (which is preferred anyway). I just ran into this issue recently when I wanted the labels turned 90 degrees ;-)!

[cvanelteren]

Thanks for cleaning up the mess @cphyc ;-)!