WGLMakie error in window event callback

[kbarros]

Execute the following code:

using WGLMakie
zs = LinRange(0, 3, 20)
xs = cos.(5zs)
ys = sin.(5zs)
fig = meshscatter(xs, ys, zs, markersize = 0.1, color = zs)
DataInspector(fig)
fig

• From the terminal, this will launch a browser tab with the 3D scene, but interactive controls are lost (for example, mouse-drag will not rotate).

• From a VSCode window, this will open a new tab with the 3D scene, interactive controls are broken in a different way, and Julia reports the following error:

┌ Warning: Error in window event callback
│   exception =
│    Session is not open and would result in this function to indefinitely block.
│            It may unblock, if the browser is still connecting and opening the session later on. If this is expected,
│            you may try setting `error_on_closed=false`
│    Stacktrace:
│      [1] error(s::String)
│        @ Base ./error.jl:35
│      [2] evaljs_value(session::JSServe.Session{JSServe.WebSocketConnection}, js::JSServe.JSCode; error_on_closed::Bool, timeout::Float64)
│        @ JSServe ~/.julia/packages/JSServe/BRpDB/src/session.jl:246
│      [3] evaljs_value(session::JSServe.Session{JSServe.WebSocketConnection}, js::JSServe.JSCode)
│        @ JSServe ~/.julia/packages/JSServe/BRpDB/src/session.jl:243
│      [4] pick_sorted(scene::Scene, screen::WGLMakie.Screen, xy::Point{2, Float32}, range::Int64)
│        @ WGLMakie ~/.julia/packages/WGLMakie/XT8NJ/src/picking.jl:53
│      [5] pick_sorted(scene::Scene, xy::Point{2, Float32}, range::Int64)
│        @ Makie ~/.julia/packages/Makie/Qvk4f/src/interaction/interactive_api.jl:124
│      [6] on_hover(inspector::DataInspector)
│        @ Makie ~/.julia/packages/Makie/Qvk4f/src/interaction/inspector.jl:304
│      [7] (::Makie.var"#1236#1240"{DataInspector})(::Tuple{Float64, Float64})
│        @ Makie ~/.julia/packages/Makie/Qvk4f/src/interaction/inspector.jl:280
│      [8] #invokelatest#2
│        @ Base ./essentials.jl:887 [inlined]
│      [9] invokelatest
│        @ Base ./essentials.jl:884 [inlined]
│     [10] notify
│        @ Observables ~/.julia/packages/Observables/YdEbO/src/Observables.jl:206 [inlined]
│     [11] setindex!(observable::Observable, val::Any)
│        @ Observables ~/.julia/packages/Observables/YdEbO/src/Observables.jl:123
│     [12] (::WGLMakie.var"#56#58"{Dict{Any, Any}, Scene, Events})()
│        @ WGLMakie ~/.julia/packages/WGLMakie/XT8NJ/src/events.jl:57
└ @ WGLMakie ~/.julia/packages/WGLMakie/XT8NJ/src/events.jl:109

The following modified code responds to events correctly, however:

using WGLMakie
begin
    zs = LinRange(0, 3, 20)
    xs = cos.(5zs)
    ys = sin.(5zs)
    fig = meshscatter(xs, ys, zs, markersize = 0.1, color = zs)
    DataInspector(fig)
    fig
end

The key difference seems to be that the modified code does not call display on the DataInspector.