Preserve marker size in scattergl traces with different glPixelRatio values

[archmoj]

Fix #3246 for scattergl trace.
Before codepen.
After codepen.

[archmoj]

https://github.com/gl-vis/regl-scatter2d/compare/fix3246-glPixelRatio-change-marker-size

[antoinerg]

Thanks @archmoj for looking into this issue! This might give a new life to my old Orca PR #3237 😄

Can you explain why we're completely dropping glPixelRatio from the regl-scatter2d module? I understand it wasn't working properly before but isn't it supposed to do something like control the resolution/sharpness of markers? @alexcjohnson was hinting at this in #3246 (comment) . I'm not really familiar with the 3D modules so it'd be nice if you could shed light upon this for me and tell me if glPixelRatio should be added in the future or not!

[archmoj]

We don't completely drop glPixelRatio from regl-scatter2d and one could find the variable all over the place. But it looks that it was applied twice in the sizes. And since the plotGlPixelRatio is generally set to 2.0 on plotly.js it is replaced by 2.0 in the vertex shader programs so that the graphs may remain unchanged.

[antoinerg]

We don't completely drop glPixelRatio from regl-scatter2d and one could find the variable all over the place. But it looks that it was applied twice in the sizes. And since the plotGlPixelRatio is generally set to 2.0 on plotly.js it is replaced by 2.0 in the vertex shader programs so that the graphs may remain unchanged.

I was misled by the bad grep command I was using. Sorry about that! I now see we're still using glPixelRatio 👍 ! I will let @etpinard review this one. Thank you again 😄

[etpinard]

Cool. Thanks @archmoj

Can you turn https://github.com/gl-vis/regl-scatter2d/compare/fix3246-glPixelRatio-change-marker-size into a PR and ping @dy ?

Tagging this under 1.46.0

[etpinard]

Dropping from 1.46.0

[archmoj]

It was better to redo the PR in #5093 than fixing these conflicts.
Closing.