scattergl fillcolor incorrect with multiple polygons in same trace when with `fill: toself`

[cpsievert]

https://codepen.io/cpsievert/pen/ZvNqjQ

Note that fillcolor renders correctly when type: scatter.

[jackparmer]

cc @Kully - this is going to be an issue with the Python county choropleth as well. Probably watch this issue and hold off on the WebGL approach until this is fixed:

[Kully]

I actually found that toself fill didn't work with just one polygon (ie list of coordinates defining a contained polygon)

But I only checked in the Python API

[jackparmer]

Here is what I get for a full US county map for SVG vs WebGL using toself:

[alexcjohnson]

related: #2450

[Kully]

Another example of the USA choropleth from here: https://plot.ly/python/county-choropleth/#the-entire-usa This is switching scatter -> scattergl in the figurefactory.

[jackparmer]

⬆️ Doesn't look like the recent scattergl fill changes fixed things for this particular use case

[etpinard]

Doesn't look like the recent scattergl fill changes fixed things for this particular use case

There haven't been any scattergl fill changes since the regl push back January.

[jackparmer]

Oh, I thought @dy had done some work on regl-line2d fills after January. I guess I'm misremembering.

[etpinard]

He's done some work. But none of which is ready to get merged at this stage.

[dy]

It is coming, after regl-text. Pls stay tuned)

[alexcjohnson]

A nice pared-down reproduction from @llnns in #2845:

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Using scattergl with toself fill option results in a "ghost"/wrong/extra fill among the first points of each object. A minimal example creating three rectangles:

https://codepen.io/anon/pen/NBvbbv

Results in:

Also, using the same data with scatter type has the expected output: