rework convert_attribute docstring

[jw3126]

supersedes #2504

[jw3126]

I have a couple of questions about this function. Is this an internal function? Is the user supposed to overload it? If so are there typical cases, when a user might want to overload this?

[jw3126]

For instance I might have a custom recipe particles that takes attributes
photoncolor and electroncolor.
Should I overload

MakieCore.convert_attributes(value, ::key"photoncolor", ::key"phsp") = convert_attributes(value, ::key"color")
MakieCore.convert_attributes(value, ::key"electroncolor", ::key"phsp") = convert_attributes(value, ::key"color")

?

[SimonDanisch]

No, this is only for atomic plot types (like scatter, mesh, etc) and gets called in the backend.
You can use to_color in your recipe for such cases...
Overloading is only useful, if you have your own custom color type and want to use it directly as a color attribute!

[jw3126]

Ok thanks! I think this can be merged. Before this PR, the docstring is really confusing:

help?> convert_attribute
search: convert_attribute

  to_color(color)


  Converts a color symbol (e.g. :blue) to a color RGBA.

  ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

  to_colormap(cm)


  Converts a colormap cm symbol/string (e.g. :Spectral) to a colormap RGB array.

  ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

  `AbstractVector{<:AbstractFloat}` for denoting sequences of fill/nofill. e.g.


  [0.5, 0.8, 1.2] will result in 0.5 filled, 0.3 unfilled, 0.4 filled. 1.0 unit is one linewidth!

  ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

  A `Symbol` equal to `:dash`, `:dot`, `:dashdot`, `:dashdotdot`


  ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

  to_volume_algorithm(b, x)


  Enum values: IsoValue Absorption MaximumIntensityProjection AbsorptionRGBA AdditiveRGBA IndexedAbsorptionRGBA

  ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

  Symbol/String: iso, absorption, mip, absorptionrgba, indexedabsorption

[SimonDanisch]

Thanks!