1901215 - Opening a large array is very slow

Status: NEW

(DevTools :: JSON Viewer, defect, P3)

Description

[Florian Quèze [:florian]]

I initially opened bug 1901204 (see the steps to reproduce there) and put it in the accessibility component as a11y code was responsible for 74% of the CPU time, but with a11y force-disabled, this is still slower than it should be. Here's a profile with a11y disabled: https://share.firefox.dev/3XcyTWQ

If this can't be made (much) faster, should the behavior used in the devtools console (where large arrays will be divided in multiple sections) be adopted instead?

Comment 1

[Julian Descottes [:jdescottes]]

It seems styles and reflows are extremely long. We do have a scrollable container in the json-viewer which might slow down things.
Let's first try to see if we can update the styles to make this faster, if not we should use buckets as in the console.