Add line.shape: 'spline' support to scattergl

[brian428]

It looks like "spline" is missing from the ScatterGL attributes file for line shape options: https://github.com/plotly/plotly.js/blob/master/src/traces/scattergl/attributes.js#L51

[etpinard]

Part of #130, but yeah this now deserves an issue of its own.

[brian428]

Oh, was "spline" never a valid option here?

[etpinard]

No. 1.42.0 added line.shape to scattergl, but w/o the 'spline' value.

[danlabici]

I was reading #130 but I wonder if there is anything more specific to watch about the progress on "spline".
(in the meantime I'm subscribed to this for updated)

[Sagaulf]

Any news on this?
Using plotly express line chart with dash. The graph is initially loaded with the 'spline' format but on a callback it fails due to scattergl.line not having 'spline' as a shape property

[ZeroCool2u]

Same issue here as @Sagaulf This seems like a bug, because the Plotly Express docs don't mention this constraint at all.

[skoeb]

Also wondering if there is a fix for this... it seems like in plotly express 'spline' works with svg as the render_mode but not auto in some circumstances.

[patryk-oleniuk]

I have the same problem.
Furthermore, depending on the amount of data (if render_mode=auto) the render mode is switched from svg to webgl. So I currently have the situation when the spline sometimes works, sometimes does not...

[valankar]

Furthermore, depending on the amount of data (if render_mode=auto) the render mode is switched from svg to webgl. So I currently have the situation when the spline sometimes works, sometimes does not...

I just spent quite awhile trying to figure out why I was getting an exception depending on how much data used, and it turned out to be this. Please fix this.