Integrate better with GeoInterface.jl and Proj.jl to plot any geoms in any projections

[rafaqz]

GeoMakie.jl could accept any geointerface geometries in any projection.

Some geometries have the projection attached already, so we could do the conversion automaticaly. Otherwise plotting onto a GeoAxis could accept a source_crs keyword and do the conversions.

If the geometries are in different projections to the map and/or each other we can reproject them with JuliaGeo/Proj.jl#79

[asinghvi17]

hmm, that sounds hard to implement if it's the object which has the projection, since we can't really dispatch on that...

[rafaqz]

We can dispatch on GeoInterface.crs(object) - it will be a GeoFormatTypes.jl wrapper. Users could also pass in crs as a keyword like poly!(geoaxis, geometries; source_crs=EPSG(4326)) when its not attached to the object.

So it would need specialisation fot those methods on GeoAxis.

Then we can use Proj.jl to reproject the geometries to the axis projection.

Its quite easily doable ;)

[asinghvi17]

We can do that...but I don't think Makie can. Maybe in the poly recipe, using a convert to a geointerface wrapper or custom wrapper type? But not generally.

[felixcremer]

Wouldn't that also be a use case for the CRS trait discussed in JuliaGeo/GeoInterface.jl#119 ?

[asinghvi17]

This is a bit orthogonal - the problem lies in extracting the CRS, not in dispatching on it. That's already implemented in the code anyway.

[rafaqz]

What is the problem extracting it exactly?

[asinghvi17]

The question, I guess, was where to perform the extraction - but I guess it's actually possible to do this in the same place we pop the source kwarg! So it's probably doable then, at least for single-argument plots.

[asinghvi17]

GeoMakie.jl/src/geoaxis.jl

Lines 817 to 830 in 8941fe9

	function Makie.plot!(axis::GeoAxis, plot::Makie.AbstractPlot)
	source = pop!(plot.kw, :source, axis.source)
	transformfunc = lift(create_transform, axis.dest, source)
	trans = Transformation(transformfunc; get(plot.kw, :transformation, Attributes())...)
	plot.kw[:transformation] = trans
	Makie.plot!(axis.scene, plot)
	# some area-like plots basically always look better if they cover the whole plot area.
	# adjust the limit margins in those cases automatically.
	Makie.needs_tight_limits(plot) && Makie.tightlimits!(axis)
	if Makie.is_open_or_any_parent(axis.scene)
	Makie.reset_limits!(axis)
	end
	return plot
	end

source would also have to check plot.args to see if they have a CRS. This won't work in recipes, but for user facing plots it's better than nothing.

[rafaqz]

Ahh no it will already be gone right? Converted to GeometryBasics with no crs?

Or is the original object still around?

[asinghvi17]

The original object should still be around in plot.args...

[rafaqz]

Ok cool, I've no idea how it works internally

[rafaqz]

You should be able to call crs on it. Or if it's a Vector, crs on the first object.

Mixed crs can be undefined 😂

[asinghvi17]

Yeah that's what I was thinking as well :D

[asinghvi17]

Here's what I'm thinking:

get_crs(obj) = get_crs(GI.trait(obj), obj)
get_crs(::GI.AbstractGeometryTrait, obj) = GI.crs(obj)
function get_crs(::Nothing, obj)
	if obj isa AbstractVector
		if GI.trait(first(obj)) isa GI.AbstractGeometryTrait
			return get_crs_vector_checked(obj)
		end
	end
	return GI.crs(obj)
end
function get_crs_vector_checked(obj)
	crs_es = GI.crs.(obj)
	if length(unique(crs_es)) == 1
		return first(crs_es)
	else
		@warn("You have tried to plot objects with conflicting CRS in the same plot call!  Assuming `crs=nothing` for now.")
		return nothing
	end
end

[asinghvi17]

This is priority after #261 and #245