scattergl open markers require explicit line width

[alexcjohnson]

In regular scatter, you don't need to specify a line width to get default width 1 for open symbols:

Plotly.newPlot(gd,[{
  y: [1, 2, 3],
  marker: {symbol: 'circle-open', size: 20},
  type: 'scatter',
  mode: 'markers'
}], {width:400, height:400})

But change this to type: 'scattergl' and the markers disappear until you put an explicit line: {width: 1} in marker.

Note that this is independent of the marker.line.width in gd._fullData, which is still 0 in the scatter example above. This means supplyDefaults doesn't need to care about marker.symbol, and importantly, if marker.symbol is an array, you can use closed symbols (with no line width) alongside open symbols (with default line width 1) without explicitly saying this is what you're doing.

cc @dfcreative @VeraZab

[etpinard]

@dfcreative

Plotly.newPlot(gd,[{
  y: [1, 2, 3],
  marker: {symbol: 'circle-open', size: 20},
  type: 'scattergl',
  mode: 'markers'
}], {width:400, height:400})

leads to

off https://github.com/plotly/plotly.js/tree/rescatter-squashed-2018

Would you mind taking a look this before we release regl?

[dy]

@etpinard @alexcjohnson thanks! Fixed by 320c4c9

[dy]

Added mock in 7cefeab

[etpinard]

closed by #2258