implement contour labels

[t-bltg]

Description

Fix #832.

Very early stage implementation, much to be discussed.

2D

using CairoMakie

main() = begin
  fig = let
    paraboloid = (x, y) -> 10(x^2 + y^2)
    x = range(-3, 3; length = 100)
    y = range(-3, 3; length = 200)
    z = paraboloid.(x, y')

    fig, ax, hm = heatmap(x, y, z; interpolate = true)
    Colorbar(fig[1, 2], hm)

    contour!(
      ax, x, y, z;
      color = :red, levels = 0:10:100, labels = true,
      labelsize = 15, labelfont = :bold, labelcolor = :orange
    )
    fig
  end

  save("contour_labels_2d.png", fig)
  fig
end

main() |> display

3D

currently failing, transformation or projection issue, comments welcome :)

using CairoMakie

main() = begin
  fig = let
    fig = Figure()
    ax = Axis3(fig[1, 1])

    xs = ys = range(-.5, .5; length = 100)
    zs = @. √(xs^2 + ys'^2)

    levels = .025:.05:.475
    contour3d!(-zs; levels = -levels, labels = true, color = :blue)  # labels inherit linecolor by default
    contour3d!(+zs; levels = +levels, labels = true, color = :red, labelcolor = :black)
    fig
  end

  save("contour_labels_3d.png", fig)
  fig
end

main() |> display

• rotate labels automagically to align on the local tangent ?
• dynamic contour label attributes (fontsize, color, ...) ?
• check fix contour3d

Type of change

Delete options that do not apply:

• New feature (non-breaking change which adds functionality)

Checklist

• Added an entry in NEWS.md (for new features and breaking changes)
• Added or changed relevant sections in the documentation
• Added unit tests for new algorithms, conversion methods, etc.
• Added reference image tests for new plotting functions, recipes, visual options, etc.

[t-bltg]

@jkrumbiegel, I'm a bit stuck in 3D.
The text bounding boxes are not correct, and I cannot find a way to fix it.
Using wireframe!(plot, bb, space = :pixel) as commented in the PR code draws the correct bboxes in the 2D examples, but renders nonsense in 3D.
I tried to lift(scene.camera.projectionview, scene.px_area) to recompute the bounding boxes but it fails.
I think it might be related to #1653, but I have no ideas left ...
Could you advise ?

[jkrumbiegel]

What do the wrong boundingboxes look like? Could also always still be a bug with space=:pixel I guess, unless you think the boundingboxes themselves are wrong somehow

[t-bltg]

If I remove the scene.camera.projectionview, scene.px_area from the listeners on bboxes computation, then no bounding box is drawn in 3D.

This explains at least why the label masking in 3D doesn't appear: I think a masked line is drawn on top of an un-masked line (before the projection matrix changes, wrong bboxes), thus hiding the masking effect.

[jkrumbiegel]

Ah Axis3 probably just doesn't ignore limits of plots with space=:pixel yet, there's still stuff to clean up.

On the second image the boxes don't look too bad right? Although not all of them are filled?

[lazarusA]

oh, this is a good one!. A pitty that is still not ready to merge.

[t-bltg]

What makes you say it isn't ?

[lazarusA]

apologies, maybe my mistake, I just saw the CI failing. And your 3d wireframe example, I don't see the current example working.

[asinghvi17]

@t-bltg mind if I merge master in?

[t-bltg]

apologies, maybe my mistake, I just saw the CI failing. And your 3d wireframe example, I don't see the current example working.

No worries.

The up-to-date examples (2D/3D) are in the first post (#2496 (comment)).

The failing CI is due to missing references images, which need to be merged by a maintainer.

[t-bltg]

Pending CI, can we get this PR in ?

[SimonDanisch]

Thank you so much for this great PR :) Sorry for taking so long...

[t-bltg]

Amazing, and many thanks to @jkrumbiegel for the hints and guidance towards (hopefully) quality code !