[$500] Web - Emojis flickers when scrolling a list of emojis and sometimes part of them disappear

[kbecciv]

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Version Number: 1.3.96.0
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 #30201

Action Performed:

1. Launch App
2. Navigate to any chat
3. Tap emoji button to open emoji picker
4. Scroll emoji list up/ down

Expected Result:

All emoji should be visible when list of emoji scrolling.

Actual Result:

Emojis flickers when scrolling a list of emojis and sometimes part of them disappear

Workaround:

Unknown

Platforms:

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

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

Screenshots/Videos

Bug6266710_1699318980930.30201_Mac_Chrome.mp4

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• Last Price Increase: 2023-12-05

[melvin-bot]

Job added to Upwork: https://www.upwork.com/jobs/~013d1a1c15ee78f5b3

[melvin-bot]

Triggered auto assignment to @adelekennedy (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 - @alitoshmatov (External)

[ZhenjaHorbach]

Proposal

Please re-state the problem that we are trying to solve in this issue.

Emojis flickers when scrolling a list of emojis and sometimes part of them disappear

What is the root cause of that problem?

The main problem is
That we have a non-optimized FlatList
Which does not have time to display new elements correctly if we swipe the list very quickly

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

We have a huge number of properties to optimize FlatList
https://reactnative.dev/docs/optimizing-flatlist-configuration

But the most optimal as for me is the addition of new properties of windowsize and updateCellsBatchingPeriod

Which will increase small memory consumption but will positively affect the display of elements

So we can add updateCellsBatchingPeriod={25} windowSize={42} for FlatList

App/src/components/EmojiPicker/EmojiPickerMenu/index.js

Lines 504 to 524 in ece8312

	<FlatList
	ref={emojiListRef}
	data={filteredEmojis}
	renderItem={renderItem}
	keyExtractor={keyExtractor}
	numColumns={CONST.EMOJI_NUM_PER_ROW}
	style={[
	listStyle,
	// This prevents elastic scrolling when scroll reaches the start or end
	{overscrollBehaviorY: 'contain'},
	// Set overflow to hidden to prevent elastic scrolling when there are not enough contents to scroll in FlatList
	{overflowY: filteredEmojis.length > overflowLimit ? 'auto' : 'hidden'},
	// Set scrollPaddingTop to consider sticky headers while scrolling
	{scrollPaddingTop: isFiltered ? 0 : CONST.EMOJI_PICKER_ITEM_HEIGHT},
	]}
	extraData={[filteredEmojis, highlightedIndex, preferredSkinTone]}
	stickyHeaderIndices={headerIndices}
	getItemLayout={getItemLayout}
	contentContainerStyle={styles.flexGrow1}
	ListEmptyComponent={<Text style={[styles.textLabel, styles.colorMuted]}>{translate('common.noResultsFound')}</Text>}
	/>

Before

Screen.Recording.2023-11-07.at.14.28.25.mov

After

Screen.Recording.2023-11-07.at.14.27.25.mov

Since this problem is specific to browsers
We can disable this for apps

What alternative solutions did you explore? (Optional)

As an alternative, we can use other properties
For example maxToRenderPerBatch + updateCellsBatchingPeriod

[daviddigital]

Proposal

Please re-state the problem that we are trying to solve in this issue.

In chrome on mac web, the emoji's flicker, particularly when scrolling fast or jumping through emoji categories

What is the root cause of that problem?

I identified that this is only happening in chrome and is fine in safari/firefox, and can be "fixed" if hardware acceleration is turned off in chrome system settings. So the root cause is a conflict with the chrome hardware acceleration and the emoji rendering. This could be because theFlatList and the renderItem is not optimised as much as possible, but tweaks didn't solve that, but rather adjusting the styling of the Text for emojiText does.

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

Removing the styling of the emojiText in the EmojiPickerMenuItem component (so its just the emoji unicode) fixes the flickering, so to fix the problem we just need to update the styling of the Text component for emojiText so that it doesn't conflict with the chrome browser on rendering as is currently happening.

As a proof of concept, if I remove all styling on emojiText, or even just the fontSize so that the Text component just renders as a unicode emoji, the flickering stops (see video).

https://github.com/Expensify/App/blob/c2e40423ac71fa67e65b570342c39e4c2b25a46f/src/styles/styles.ts#L1868C1-L1875C1

Note in the solution the styling will match the current styling, this is a POC.

https://imgur.com/a/HQPsc7n

https://imgur.com/a/5fiUw8V

What alternative solutions did you explore? (Optional)

I looked into the FlatList implementation on the EmojiPickerMenu component on to see if there were performance improvements but they didn't fix the problem.

[melvin-bot]

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