⚗ Collect scroll metrics

[hamza-kadiri]

Motivation

We want to track scoll metrics.

RFC: https://docs.google.com/document/d/1_5wSVrqVD6_UF93Pag3xQYlFUDeTwVHS5BJb78RjZb4/edit?tab=t.0#heading=h.rnd972k0hiye

Changes

• update trackViews to add scroll metrics
• add these metrics to the view event

Testing

This PR is not production ready yet, it's intended to deploy it to staging first

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[bits-bot]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

Merging #2180 (131d2f7) into main (629ebbf) will increase coverage by 0.05%.
The diff coverage is 84.61%.

@@            Coverage Diff             @@
##             main    #2180      +/-   ##
==========================================
+ Coverage   94.17%   94.22%   +0.05%     
==========================================
  Files         205      206       +1     
  Lines        6144     6180      +36     
  Branches     1361     1368       +7     
==========================================
+ Hits         5786     5823      +37     
+ Misses        358      357       -1     

Impacted Files	Coverage Δ
.../rum/src/domain/record/observers/scrollObserver.ts	25.00% <ø> (ø)
packages/rum/src/domain/record/record.ts	79.06% <ø> (ø)
packages/rum/src/domain/record/viewports.ts	82.35% <ø> (+9.62%)	⬆️
packages/rum-core/src/browser/scroll.ts	62.50% <62.50%> (ø)
...omain/rumEventsCollection/view/trackViewMetrics.ts	97.84% <93.75%> (-2.16%)	⬇️
packages/core/src/tools/experimentalFeatures.ts	100.00% <100.00%> (ø)
.../src/domain/rumEventsCollection/view/trackViews.ts	100.00% <100.00%> (ø)
.../domain/rumEventsCollection/view/viewCollection.ts	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes

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[bcaudan]

❓ question: a fair amount of views don't have loading time, could it be bothering to not have scroll information for those views?
why not doing it at init?‏

[hamza-kadiri]

It's not really a problem to not have scroll information for all the views, we can consider that this information is saved only when the user has spent enough time on the view (i.e. it has at least finished loading). Loading time is intersting because the page has usually reached a state where metrics like the scroll height are stable. It's true that it's not 100% reliable though, we sometimes send values before the page is fully loaded (See how small the scroll height can be here)

[bcaudan]

❓ question: ‏why maxScrollDepthTime should be related to loadingTime in this case?

[hamza-kadiri]

I kind of explain this in my previous comment, I think it's not ideal because the page is often not fully loaded at "loading time" I'm open to suggestions on how to improve this

[ThibautGeriz]

LGTM for replay

[bcaudan]

💬 suggestion: ‏reinforce naming and avoid confusion with the other getScrollMetrics

Suggested change

	getScrollMetrics = computeScrollValues
	getScrollValues = computeScrollValues