support alpha argument in band()

[aplavin]

Description

The alpha argument was just silently ignored before this PR. This makes it actually work.

Type of change

Delete options that do not apply:

• Bug fix (non-breaking change which fixes an issue)

Checklist

• Added reference image tests for new plotting functions, recipes, visual options, etc.

[aplavin]

bump :)

[jkrumbiegel]

can't mesh receive the alpha attribute itself, forwarded?

[aplavin]

Not sure how it all works together... From the code around, seems like all attrs are already forwarded to mesh, but specifying alpha for band plots doesn't work for now.

[jkrumbiegel]

@SimonDanisch is mesh expected to support alpha?

[aplavin]

bump...
band with alpha would be convenient

[SimonDanisch]

This is a CairoMakie issue, so I don't think this is the correct fix.
GLMakie works fine:

using GLMakie
xs = 1:0.2:10
ys_low = -0.2 .* sin.(xs) .- 0.25
ys_high = 0.2 .* sin.(xs) .+ 0.25

band(xs, ys_low, ys_high, alpha=0.5)

I'm guessing the problem is in https://github.com/MakieOrg/Makie.jl/blob/master/CairoMakie/src/overrides.jl?

[jkrumbiegel]

A right of course, it's just the override that ignores it.

[aplavin]

Should be fixed properly now! Local testing with CairoMakie shows band transparency.

[aplavin]

bump...
closes #3356

[SimonDanisch]

Sorry for the long wait, these overrides are a bit hacky and not that great to review for me, since it's not quite clear to me what the "correct" way of doing things is here.
I think we should just merge this, and clean up the overrides once we support having backends decide which plots are "atomic".
@jkrumbiegel does that sound good?

[SimonDanisch]

Thank you!