[$500] Chat - Skeleton is displayed at beginning, then a black area appears

[lanitochka17]

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Version Number: 1.3.98-0
Reproducible in staging?: Y
Reproducible in production?: Y
If this was caught during regression testing, add the test name, ID and link from TestRail:
Email or phone of affected tester (no customers):
Logs: https://stackoverflow.com/c/expensify/questions/4856
Expensify/Expensify Issue URL:
Issue reported by: Applause - Internal Team
Slack conversation:

Issue found when executing PR #30774

Action Performed:

re-requisite: must be logged in and have a chat with a lot of messages

1. Open a chat where you have a lot of messages
2. Scroll up many times to load previous messages on chat

Expected Result:

Skeleton should appear every time the chat loads

Actual Result:

Skeleton is displayed at beginning, then a black area appears and loading previous messages has an unusual behavior

Workaround:

Unknown

Platforms:

Which of our officially supported platforms is this issue occurring on?

• Android: Native
• Android: mWeb Chrome
• iOS: Native
• iOS: mWeb Safari
• Windows: Chrome
• MacOS: Desktop

Screenshots/Videos

Add any screenshot/video evidence

Bug6271542_1699637392653.bandicam_2023-11-10_12-57-21-126.mp4

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Upwork Automation - Do Not Edit

• Upwork Job URL: https://www.upwork.com/jobs/~012f353b1fa07d8bce
• Upwork Job ID: 1723031808885907456
• Last Price Increase: 2023-11-17

[melvin-bot]

Job added to Upwork: https://www.upwork.com/jobs/~012f353b1fa07d8bce

[melvin-bot]

Triggered auto assignment to @miljakljajic (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details.

[melvin-bot]

Bug0 Triage Checklist (Main S/O)

• This "bug" occurs on a supported platform (ensure Platforms in OP are ✅)
• This bug is not a duplicate report (check E/App issues and #expensify-bugs)
  • If it is, comment with a link to the original report, close the issue and add any novel details to the original issue instead
• This bug is reproducible using the reproduction steps in the OP. S/O
  • If the reproduction steps are clear and you're unable to reproduce the bug, check with the reporter and QA first, then close the issue.
  • If the reproduction steps aren't clear and you determine the correct steps, please update the OP.
• This issue is filled out as thoroughly and clearly as possible
  • Pay special attention to the title, results, platforms where the bug occurs, and if the bug happens on staging/production.
• I have reviewed and subscribed to the linked Slack conversation to ensure Slack/Github stay in sync

[melvin-bot]

Triggered auto assignment to Contributor-plus team member for initial proposal review - @getusha (External)

[melvin-bot]

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[adarkforce]

Contributor details
Your Expensify account email: a.dellafortuna00@gmail.com
Upwork Profile Link: https://www.upwork.com/freelancers/~01b4d8d8ede39fdc74

[melvin-bot]

✅ Contributor details stored successfully. Thank you for contributing to Expensify!

[adarkforce]

Proposal

Unusual scrolling behaviour with performance degradation, causing weird jumps and inconsistent scroll behaviour.
PS: on my machine it was VERY laggy.

What is the root cause of that problem?

Performance degradation.

• maxToRenderPerBatch forced to 1.
• BaseInvertedFlatList usinggetItemLayout

What changes do you think we should make in order to solve the problem?

The main issue was the BaseInvertedFlatList component having to measure items layout, removing all the related code along with forced windowSize made the component faster and more responsive.

The list stopped in iOS Safari when reaching the top. This was mainly due to maxToRenderPerBatch set to 1 in BaseInvertedFlatList component, it could be safely removed because #24482 has been merged.
This, along with removing onEndReachedThreshold and onStartReachedThreshold made the scrolling experience faster and more consistent.

After the fix, when scrolling fast, the component can result in showing blank rows.
Readjusting for example maxToRenderPerBatch could improve it, but I don't think there's need to, as well as an event signalling the fact that the view is full of items that are not ready to render (blank).
The rows now appear faster, and It seems that the overall user experience is largely improved.

We can also render ReportActionsSkeletonView when
reportMetadata.isLoadingNewerReportActions or reportMetadata.isLoadingOlderReportActions is true, to show the skeleton while loading new data, but it doesn't seem strictly necessary

[miljakljajic]

This is linked to newDot performance issues which we're discussing internally - raised it in #newdot-performance and will share next steps soon

[melvin-bot]

📣 It's been a week! Do we have any satisfactory proposals yet? Do we need to adjust the bounty for this issue? 💸

[getusha]

Not able to reproduce this one
@lanitochka17 @miljakljajic @adarkforce

[miljakljajic]

Checking with Applause as they reported this one!

[miljakljajic]

Not reproducible: https://expensify.slack.com/archives/C9YU7BX5M/p1700590625655629