Concatenation distorts interactive legend

[lbittarello]

Sorry if this issue has been reported before!

Consider this example from the documentation:

import altair as alt
from vega_datasets import data

cars = data.cars.url

selection = alt.selection_multi(fields=["Origin"])

color = alt.condition(
    selection, alt.Color("Origin:N", legend=None), alt.value("lightgray")
)

scatter = (
    alt.Chart(cars)
    .mark_point()
    .encode(x="Horsepower:Q", y="Miles_per_Gallon:Q", color=color, tooltip="Name:N")
)

legend = (
    alt.Chart(cars)
    .mark_point()
    .encode(y=alt.Y("Origin:N", axis=alt.Axis(orient="right")), color=color)
    .add_selection(selection)
)

scatter | legend

produces

However, if we change the last line to

alt.vconcat(scatter) | legend

we get

This seems to be a regression – both plots look the same with Altair 4.1.0.

[jakevdp]

Thanks for the report! It seems to be a change in Vega-Lite's default layout. I'm not sure whether it's a bug or intended behavior in the vega-lite renderer

[joelostblom]

This is working for me as expected when installing Altair directly from the GitHub repos main branch so it must have been fixed in later versions of VL although I did find a few issues that seem related:

• https://github.com/vega/vega-lite/pull/6226
• https://github.com/vega/vega-lite/pull/6095
• https://github.com/vega/vega-lite/issues/6209
• https://github.com/vega/vega-lite/issues/6277 (open)

[mattijn]

Fine for me too on development version. Closing seems fine then.