plotGlPixelRatio has no effect on scattergl

[archmoj]

demo

[jonmmease]

Looking at https://www.khronos.org/webgl/wiki/HandlingHighDPI, I wonder if we need to use a larger canvas size here:

plotly.js/src/plot_api/plot_api.js

Lines 225 to 227 in 7347bed

	fullLayout._glcanvas
	.attr('width', fullLayout.width)
	.attr('height', fullLayout.height);

This doesn't work on its own, but something like:

            fullLayout._glcanvas
                .attr('width', fullLayout.width * config.plotGlPixelRatio)
                .attr('height', fullLayout.height * config.plotGlPixelRatio)
                .style('width', fullLayout.width)
                .style('height', fullLayout.height);

In this case, I think we would not want to use a constant marker size (#5093).

But I don't understand this very well. And not sure why it wouldn't be an issue with gl3d plots.

[jonmmease]

Looks like this is what scatter3d is doing:

https://github.com/gl-vis/gl-plot3d/blob/0ae1280e1d366fcf96419b6acd85c194ee1f43a6/scene.js#L253-L266

    var nextWidth  = Math.ceil(width  * scene.pixelRatio)|0
    var nextHeight = Math.ceil(height * scene.pixelRatio)|0
    if(nextWidth !== canvas.width || nextHeight !== canvas.height) {
      canvas.width   = nextWidth
      canvas.height  = nextHeight
      var style = canvas.style
      style.position = style.position || 'absolute'
      style.left     = '0px'
      style.top      = '0px'
      style.width    = width  + 'px'
      style.height   = height + 'px'
      dirty = true
    }

[archmoj]

Looking at https://www.khronos.org/webgl/wiki/HandlingHighDPI, I wonder if we need to use a larger canvas size here:

plotly.js/src/plot_api/plot_api.js

Lines 225 to 227 in 7347bed

	fullLayout._glcanvas
	.attr('width', fullLayout.width)
	.attr('height', fullLayout.height);

This doesn't work on its own, but something like:

            fullLayout._glcanvas
                .attr('width', fullLayout.width * config.plotGlPixelRatio)
                .attr('height', fullLayout.height * config.plotGlPixelRatio)
                .style('width', fullLayout.width)
                .style('height', fullLayout.height);

In this case, I think we would not want to use a constant marker size (#5093).

But I don't understand this very well. And not sure why it wouldn't be an issue with gl3d plots.

In that case perhaps we also need to patch reg-line2d and some other modules to take into account pixelRatio.

[jonmmease]

I think I have a solution... Will open WIP PR in a bit.

Edit: only needs plotly.js updates