Ha. regl must be invoking one or many globals that IE9 doesn't support at runtime.

As this file here plot_api.js is required in all partial bundles (even that gl-less ones), this makes the IE9 test fail.

So, I think the best to solve this would be use a Registry.getComponentMethod-style pattern so that regl is only required in bundles that expose regl traces.

@etpinard do I get it right that we don't have this safe-require pattern yet? What if I just require regl directly when the regl trace type is detected?

What if I just require regl directly when the regl trace type is detected?

You mean something like:

if(fullLayout._has('regl')) {
  var createREGL = require('regl')
}

in plot_api.js? That could work, but regl would still get bundled up in all partial bundles.

Why change [0] to [{}]?

brilliant ✨

Lovely cleanup ❤️

what about this one here?

that is the way parcoords is doing it's thing: https://github.com/plotly/plotly.js/pull/2159/files#diff-2fad23de82bf8c7625ea8e11436233b7R290
I did not really try to figure out why it is done this and not the another way. Before it used own container for storing this data. If that matters, I can try to keep this object within parcoords use.

Does it work ok with data([0])?

@etpinard that is the point that parcoords puts vm property there via extendFlat, that is why it should be an object. Probably it is possible to find a better storage for it, I just did not figure out what.

I think you need a key-function here to make sure to not create these canvas nodes on every hard redraw that go through drawFramework.

Sometime like:

fullLayout._glcanvas = fullLayout._glcontainer.selectAll('.gl-canvas').data([{
  /* .. as currently ... */
}], function(d) { return d.key; });

This makes me wonder: we probably don't have sufficient test coverage for Plotly.restyle calls that morph a gl-based trace types into a SVG-based. For example off the regl2d branch we should have:

Plotly.newPlot(gd, [{
  type: 'scattergl',
  // ...
}])
.then(function() {
   d3.selectAll('canvas').size() // => 3

  return Plotly.restyle(gd, 'type', 'scatter')
})
.then(function() {
  d3.selectAll('canvas').size() // => 0
})

As restyling a parcoords traces into any other trace types doesn't make much sense at the moment. You could instead try something like:

Plotly.newPlot(gd, [{
  type: 'parcoords',
  // ...
}])
.then(function() {
   d3.selectAll('canvas').size() // => 3

  return Plotly.deleteTraces(gd, [0])
})
.then(function() {
  d3.selectAll('canvas').size() // => 0
})

oldFullLayout._glcontainer.selectAll('.gl-canvas').remove()

should suffice.