Moving the mouse over a line of the Marker Chart containing many markers is janky

[fqueze]

Example profile with many marker: https://share.firefox.dev/3erEIt3

It was displayed fullscreen on my 27" hidpi external screen, that likely didn't help.

Here is a profile of the janky interaction: https://share.firefox.dev/3vfwABR

┆Issue is synchronized with this Jira Task

[julienw]

I don't see a problem on the marker chart (that's the panel at the bottom), but I definitely see a problem in the marker track in the timeline (at the top).

I don't have a 27" screen so maybe that could appear with a bigger resolution though? @fqueze if you can confirm what you're seeing that would be wonderful :-) Thanks! Confirmed over Matrix that this happens in the Marker chart for him. His screen is a 27" 4K, so this means a lot more pixels.

We should likely try to repaint a lot less stuff on hover. By storing the previous hovered item, it should be possible to redraw only what's around it.

[rashadmad]

Greetings I am participating in the Outreachy program could I pick up this issue. I have strong javaScript experience would that bold well with the problem?

[julienw]

hey @rashadmad, you can have a look, but please know that this project isn't part of Outreachy in this round. Also we won't be able to provide a lot of guidance so we expect you to be able to investigate and fix this issue by yourself. Of course we can give a few pointers. Are you still interested?