text bounding box in an axis

[dgleich]

There appear to be some issues with text bounding boxes when used within an axis. Especially when the axis is scaled by a transform.

Expected behavior

using CairoMakie, StableRNGs
x = cumsum(randn(StableRNG(1), 100).^2)
f = lines(x,  axis=(yscale=log10,))
lbl = text!(f.axis, text="Direct Labels are Great!", 50, 50, align=(:right,:bottom))
bb = boundingbox(lbl)
wireframe!(f.axis, bb, color=:red, space=:data)
f

shows a bounding box around the text string.

Instead, this shows:

Changing wireframe!(f.axis, bb, color=:red, space=:data) to wireframe!(f.axis.scene, bb, color=:red, space=:pixel) shows no bounding box. Adding campixel(f.axis.scene) does not work either. Plotting text! into f.axis.scene also made no difference.

Where we do see somewhat expected behavior

using CairoMakie, StableRNGs                                                                                                                                                                                                 
x = cumsum(randn(StableRNG(1), 100).^2)
f = lines(x) # CHANGE, no log10 scale...
scene = campixel(f.axis.scene) # CHANGE
lbl = text!(scene, 200, 200, text="Direct Labels are Great!", align=(:right,:bottom),space=:pixel)                 
bb = boundingbox(lbl)                                                                               
wireframe!(scene, bb, color=:red, space=:pixel)         
f

This does work, but requires pixel coordinates for the text rather than data coordinates.

This also fails with specifying a logscale y axis...

using CairoMakie, StableRNGs                                                                                                                                                                                                 
x = cumsum(randn(StableRNG(1), 100).^2)
f = lines(x, axis=(yscale=log10,)) # CHANGE, log10 scale...
scene = campixel(f.axis.scene) # CHANGE
lbl = text!(scene, 200, 200, text="Direct Labels are Great!", align=(:right,:bottom),space=:pixel)                 
bb = boundingbox(lbl)                                                                               
wireframe!(scene, bb, color=:red, space=:pixel)         
f

This was verified on the most recent versions I could update to of CairoMakie (CairoMakie v0.9.2) and Makie (Makie v0.18.2)

See origin of this discussion here:
https://discourse.julialang.org/t/automatic-direct-labels-for-makie-with-voronoi-tessellation/90247/4

[jkrumbiegel]

The boundingbox behavior is indeed not great right now. I think there need to be different methods (or at least keyword args) to decide what you want to draw the box around. Currently it's a bit arbitrary that you get a pixel boundingbox, because as you noticed you cannot use this to envelop the text in data coordinates (what the usual use of a boundingbox is).

Also I think log transform and space = :pixel don't play well together, because it seems to be the transform is also applied on the wireframe in the last example, even though in space = :pixel it doesn't make sense. That would be an easier fix, but we need to make sure we settle on one consistent behavior everywhere.

[dgleich]

Okay, thanks for the info. Sounds like things are still getting sorted out. I appreciate the complexity of the issues involved :)

In case it helps at all with thinking about use cases, the use case I want is to figure out if/how a text label overlaps with a line/scatter plot. And if so, then I can nudge a text label away from a line/points. So what seems like "ideal" scenario for me would be to able to get line/scatter data and text bounding box data in pixel space (so that I don't have to deal with any wacky data -> pixel space transformations). And then actually place the label in pixel space too... although I may have to think harder about how to do some of these things.

More notes on the motivation and setup I'm thinking of here:

• https://discourse.julialang.org/t/automatic-direct-labels-for-makie-with-voronoi-tessellation/90247
• https://github.com/dgleich/MakieDirectLabels/blob/main/label-explainer.md and the original idea
• https://observablehq.com/@harrystevens/directly-labelling-lines

[jkrumbiegel]

I have internally used functions like Makie.project or Makie.scene_to_screen to do the projection into pixel space whenever I needed it. This gives you pixel space data, you can do your calculations with that and place the resulting text with space = :pixel as you had already figured out. If a plot using that space looks buggy, for example on a transformed axis, that's a bug and should be fixed.

The projection functions are not public api right now because they grew organically as needed and there's some code duplication in there as well I think. So they would be bound to change a bit when turned into public api, but I'd definitely would like this area to solidify because it's a common enough need for more complex plots.

[jkrumbiegel]

And there's no easy method right now to get a boundingbox of text in pixels without plotting the text (I guess you'd want your bbox before plotting so you'd know where to plot? Of course you could technically plot and shift, but that seems less clean). The functions to do the boundingbox calculations are all there, but they operate on GlyphCollection so you first need to pass your text with all its visual attributes that affect boundingboxes through the layouting algorithm and then use the resulting glyph collections.

[dgleich]

Just a quick note that there is already an open issue on the transformation being applied to other spaces besides just data: #2065

[dgleich]

Here is code that now works to accomplish this goal on Master.

using CairoMakie, StableRNGs
x = cumsum(randn(StableRNG(1), 100).^2)
f = lines(x,  axis=(yscale=log10,))
lbl = text!(f.axis, text="Direct Labels are Great!", 50, 50, align=(:right,:bottom))
bb = map(f.axis.scene.camera.pixel_space, f.axis.scene.camera.projectionview, lbl) do _, _, lbl
  boundingbox(lbl)
end
wireframe!(f.axis, bb, color=:red, space=:pixel)
f