Bug: extra keyword arguments ignored for ternary density plots (e.g. vmax)

[morganjwilliams]

Describe the bug

Specifically for density plots on ternary axes, because of the introspection used by pyrolite together with how indirection/handler functions are structured within mpltern, and the fact that pyrolite uses the e.g. tripcolor variants, extra keyword arguments including vmax are not passed through to the relevant pcolor/pcolormesh functions in matplotilib

To Reproduce

import matplotlib.pyplot as plt
import numpy as np
 
import pyrolite.plot
from pyrolite.util.synthetic import normal_frame
 
# ternary random data, with a specific composition
# broad enough distribution to visualize colormapped values
df = normal_frame(
    size=1000,
    seed=11,
    columns=["SiO2", "CaO", "MgO"],
    mean=np.array([0.1, 0.4, 0.3]),
    cov=0.1 * np.array([[1.2, -0.15], [-0.15, 1.2]]),
)

ax = df.pyroplot.density(vmax=0) 

Expected behavior

Keyword arguments are passed through to the relevant pcolor/pcolormesh functions in matplotilib.

Temporary Workaround:

For at least some parameters, some attributes of e.g. the colormap and norm are able to be modified after the collection has been added to an axis; this requires a bit of reading through the properties of the collection, but makes styling changes possible, e.g.:

# set the `vmax` property of the norm from the last collection added to the axes
ax.collections[-1]._norm.vmax = 0

[morganjwilliams]

One way to patch this (in lieu of a likely future PR to mpltern adding this to the assorted axes plotting methods), is as follows, adding relevant keyword arguments to mpltern._axes.TernaryAxes.tripcolor:

from functools import wraps

import mpltern
from mpltern.ternary_parsers import _parse_ternary_single

@_parse_ternary_single
def _tripcolor(self,
    *args,
    alpha=1.0,
    norm=None,
    cmap=None,
    vmin=None,
    vmax=None,
    shading='flat',
    facecolors=None,
    **kwargs,
):
	return super(mpltern.ternary._axes.TernaryAxes, self).tripcolor(*args, 
                      alpha=alpha,
                      norm=norm,
                      cmap=cmap,
                      vmin=vmin,
                      vmax=vmax,
                      shading=shading,
                      facecolors=facecolors,
                      **kwargs,
                      )

mpltern.ternary._axes.TernaryAxes.tripcolor = _tripcolor