scattergl lines sometimes draws random lines on some hardware

I’ve posted this in the forum: https://community.plot.ly/t/scattergl-causes-strange-lines-to-be-drawn/19189

After investigating a bit further, I’m filing a bug/issue here.

The issue is that when the type is set to scattergl, sometime the plot will draw random lines extending across the plot. It doesn’t seem to happen every time, but I can see it consistently on the example with many points: https://plot.ly/python/webgl-vs-svg/

It seems to be dependent on the size of the chart, if I resize my browser window and refresh that example, sometimes the lines appear, sometimes they don’t, but it’s consistent for that size of my browser window.

I’ve added a codepen to randomly draw lines, and if I run it a few times, then I run into the issue: https://codepen.io/anon/pen/qgpbKq

For example, one time after running there was as red/blue line across the entire graph:

I would provide the exact data set, but as mentioned at the top, it seems to be dependent on the size of the window/plot being drawn (and possibly other factors?), but you should see the error if you run the code pen a few times.

Any idea what could be causing this? scattergl is great for the performance improvements, but looks broken when it’s drawing random lines across the whole plot.

Issue observed in both Chrome/FireFox, some more details:

Platform:	MacIntel
Browser User Agent:	Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36
Context Name:	webgl2
GL Version:	WebGL 2.0 (OpenGL ES 3.0 Chromium)
Shading Language Version:	WebGL GLSL ES 3.00 (OpenGL ES GLSL ES 3.0 Chromium)
Vendor:	WebKit
Renderer:	WebKit WebGL
Unmasked Vendor:	NVIDIA Corporation
Unmasked Renderer:	NVIDIA GeForce GT 750M OpenGL Engine

[jackparmer]

This issue has been tagged with NEEDS SPON$OR

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[JamesXNelson]

I had tried to reproduce on ubuntu and was not able to.

I even tried to get the graphical / hardware settings on a mac that could 100% reproduce to match the ubuntu machine that couldn’t, and it changed nothing. Mac rendered the messed up graph 100%, ubuntu, 0%.