line chart with different point marker?

How can I give different lines a different type of point marker, say a cross (+) symbol? For example, the following chart with point=True will have data points as solid circle, but it won’t work well when print black & white.

import altair as alt
from vega_datasets import data

source = data.stocks()

alt.Chart(source).mark_line(point=True).encode(
    x='date',
    y='price',
    color='symbol'
)

[jakevdp]

You can get the result you want by carefully defining legends and scale resolution:

import altair as alt
from vega_datasets import data

source = data.stocks()

line = alt.Chart(source).mark_line().encode(
    x='date',
    y='price',
    color=alt.Color('symbol', legend=None)
)

points = line.mark_point(filled=True).encode(
    color='symbol',
    shape='symbol'
)

alt.layer(
    line,
    points
).resolve_scale(
    color='independent',
    shape='independent'
)

[jakevdp]

In Altair’s docs, it’s under shape here: https://altair-viz.github.io/user_guide/marks.html#mark-properties