[BUG]: Some plots render incorrectly when using virtual-webgl in Chromium browsers

Description

Some plots are rendering incorrectly (missing or muted colors) when using virtual-webgl in Chromium based browsers. This was originally reported in plotly/Kaleido#375.

Screenshots/Video

Without virtual-webgl	With virtual-webgl

See plotly/Kaleido#375 for more examples.

Steps to reproduce

• Start plotly.js devtools
• Open the mock 'gl2d_parcoords_constraints'
• Note that there are number of dark red lines on the left side of the plot
• Edit devtools/test_dashboard/index.html to include the following <script> tag in the body

  <script src="../../node_modules/virtual-webgl/src/virtual-webgl.js"></script>
  

• Reload the mock
• Note that a few of the dark red lines are now missing

Notes

• This bug was discovered when development of Kaleido v1 started
• The previous version of Kaleido (v0.2.1) used Chromium v88. Kaleido v1 uses the installed Chromium version (usually a pretty recent one).
• At some point between the release of Chromium v88 and Chrome v112 (the oldest Chrome for Testing available here), the bug was introduced
• It's unclear if it's a bug in Chromium, a bug in virtual-webgl, or a bug in plotly.js
• Firefox doesn't have the issue, though colors do appear to render a differently for some plots when using/not using virtual-webgl
• Chromium v147 shows the following console warnings when using virtual-webgl:

  virtual-webgl.js:389 WebGLRenderingContext.canvas is not supported
  (anonymous) @ virtual-webgl.js:389
  (anonymous) @ virtual-webgl.js:1008
  virtual-webgl.js:389 WebGLRenderingContext.drawingBufferColorSpace is not supported
  (anonymous) @ virtual-webgl.js:389
  (anonymous) @ virtual-webgl.js:1008
  virtual-webgl.js:389 WebGLRenderingContext.unpackColorSpace is not supported
  (anonymous) @ virtual-webgl.js:389
  (anonymous) @ virtual-webgl.js:1008
  virtual-webgl.js:389 WebGLRenderingContext.drawingBufferFormat is not supported
  (anonymous) @ virtual-webgl.js:389
  (anonymous) @ virtual-webgl.js:1008
  

• Firefox v145 shows the following console warnings when using virtual-webgl:

  WebGLRenderingContext.canvas is not supported <anonymous code>:formatted:8942:27
  WebGLRenderingContext.drawingBufferColorSpace is not supported <anonymous code>:formatted:8942:27
  WebGLRenderingContext.unpackColorSpace is not supported <anonymous code>:formatted:8942:27
  

• virtual-webgl support was added in plotly.js in #6784

devtools/test_dashboard/index.html に追加された gl2d_parcoords_constraints mock と virtual-webgl スクリプトを使って問題を再現します。影響を受けた Chromium の動作を Firefox およびレポートに記載されている Chromium のバージョンと比較し、欠落している線の原因が Chromium、virtual-webgl、plotly.js のいずれにあるのかを特定します。virtual-webgl でプロットが一貫してレンダリングされれば完了です。