[CairoMakie] Polygons transformed to have `Inf` values drag to the top left edge of the screen about makie.jl HOT 10 OPEN

Will take a look! I suspect this is a result of CairoMakie drawing the polygons incorrectly when they are outside the bounds of the projection.

Do you get the same issue with GLMakie?

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This is a CairoMakie issue, so I'll see about transferring the issue to the Makie repo.

My first thought is that this is caused by the clamp in CairoMakie's project method - it should instead set coordinates to NaN.

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I want to refactor the way all transforms work at some stage, so this would definitely be a target for that refactor!

The primary issue is that there's no completely reliable way to get the bounding polygon for an arbitrary projection (as far as I understand it, at least) without defining it yourself (as, for example, Cartopy has done).

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Plotting lines on top is not a problem, neither is the problem resolved with a different perspective

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Haven't checked will report back

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Not a problem with GLMakie

So should this issue go over to Makie/CairoMakie? Or is that something that needs fixing here?

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Here's a more minimal MWE:

fig = Figure()
ga = GeoAxis(fig[1, 1]; dest = "+proj=ortho +lon_0=0 +lat_0=30")
lines!(ga, GeoMakie.coastlines())
poly_in_bounds = GI.Polygon([GI.LinearRing(Point2f[(72, 19), (100, 19), (100, 39), (72, 39), (72, 19)])])
poly_out_bounds = GI.Polygon([GI.LinearRing(Point2f[(72, 19), (120, 19), (100, 39), (72, 39), (72, 19)])])
poly!(ga, poly_in_bounds; color = (:red, 0.5))
poly!(ga, poly_out_bounds; color = (:yellow, 0.5))
fig

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Even more minimal:

fig = Figure()
ax, p1 = poly(fig[1, 1], GI.Polygon([GI.LinearRing(Point2f[(72, 19), (100, 19), (100, 39), (72, 39), (72, 19)])]))
p2 = poly!(ax, GI.Polygon([GI.LinearRing(Point2f[(72, 19), (Inf, 19), (100, 39), (72, 39), (72, 19)])]))
fig

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With a patch to not draw any polygon segment which is not finite, I get:

This is suboptimal, since some areas which should be shaded are not shaded, but better this than nothing I think.

From the GeoMakie perspective, the only way to do this is correctly is by intersecting the boundary line of the polygon with the boundary line of the visible Earth. Cartopy does this by manually defining the boundary of the projection, and I suspect that at some point we will have to do the same.

From a Makie perspective, this is also not great. Note that, ideally, this should have drawn the yellow box leading towards infinity to the bottom right, but here is drawing to the top left of the screen (not the plot) since the infinity is apparently getting translated to 0.

From my testing, GLMakie either segfaults or refuses to draw such invalid polygons, so perhaps CairoMakie not drawing this polygon is more in line with expected behaviour.

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I don't know how this works under the hood but could you clamp vertices of polygons that are partially outside? In the end an orthographic projections always maps onto a disc so a check like x^2 + y^2 > radius could be the basis of this?

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