Avoid line-wrapping artifacts

[aplavin]

upd 2025: call MakieExtra.GeoAxis_splitwrap!() before all GeoAxis plotting to avoid these artifacts

A simple line plot like

lines(
	[(x, x/4) for x in range(0, 300, length=100)];
	axis=(;type=GeoAxis)
)

results in

with a clear wrapping artifact. It's possible to manually split the line into multiple separate ones, or add a NaN point in the middle – but would be great to have it automatically :) Also, different projections may presumably have different wrapping lines, right?

Probably relevant to #290, but could be easier :)

[asinghvi17]

This and #290 are all symptoms of the same problem - Makie does not know the nature of a geographic transformation, and so cannot rescale / resample accordingly. All the tools to do that live in GIS world, it's just that Makie doesn't know how to use them :(

This is part of a larger refactor that we have to do to make transform_funcs easier to use in general, for which GeoMakie currently has several hacks :)

But for now, @gaelforget implemented a line splitting algorithm in https://github.com/MakieOrg/GeoMakie.jl/blob/master/src/linesplitting.jl that should help - you just call split(linestring::GeometryBasics.LineString, ga::GeoAxis) and it gives you a "split-up" line

[asinghvi17]

JuliaGeo/GeometryOps.jl#283 contains some code that will solve this for all geometries, and MakieOrg/Makie.jl#4630 may introduce a mechanism that will allow GeoMakie transform funcs to operate on geometry as well.

[aplavin]

In the meantime, just call MakieExtra.GeoAxis_splitwrap!() before doing GeoAxis plotting, and lines + polygons will automatically be cut to avoid artifacts.

The actual implementation is in https://github.com/JuliaAPlavin/MakieExtra.jl/blob/00000000c7ca5b037a54c87203bab78b6a4013d3/ext/GeoMakieExt.jl#L57-L122, I think a pretty simple extensible mechanism. The only issue is that it always cuts at +- half a turn, I don't know how to extract the antimeridian from a GeoAxis (https://github.com/JuliaAPlavin/MakieExtra.jl/blob/00000000c7ca5b037a54c87203bab78b6a4013d3/ext/GeoMakieExt.jl#L48).