Using ylim() with subplots does not properly redraw

[Modiug]

Versions:
Runtime: 0.41.0
Python: 1.11.0

The following script illustrates the issue. You will see double drawings in the second subplot.

import gr
from gr.pygr import mlab

import numpy as np

x = np.linspace(-4, 4, 100)

mlab.figure()

mlab.subplot(2,1,1)
mlab.plot(x, np.sin(x))
mlab.ylim(-2, 2)

mlab.subplot(2,1,2)
mlab.plot(x, np.cos(x) + 1)
mlab.ylim(-4, 4)

The example is using the Python wrapper, but I guess this is more an issue of the underlying framework.

Well, by looking at the Python wrapper code I got aware that I could also pass ylim=(...) to the plot command directly. That solves my issue, so no high urgency on this one.

Regards
Guido

[FlorianRhiem]

This is an issue with the subplot implementation in the Python-Wrapper. The subplot logic works by not clearing the workstation except for the first subplot. As methods like ylim cause a redraw of the current (sub)plot, this can lead to the problem you are describing.

The subplot logic needs to be reworked in general, due to other problems as well.

[Modiug]

Indeed, I see more issues when trying to use things like hold(), ylabel() and legend(). OK, best to stay away from subplot() for now.

Background: I wanted to use some live plotting of measured signals in a GUI application. Matplotlib is rather slow, therefore GR. I was using the mlab wrapper for convenience. I should better use the GR API directly.