New Lines Hidden in Block and New Block Takes a Long Time to Load

[ChrissiePollock]

Describe the bug A customer came in saying: I am still dealing with a lag in expanding the box when I get to a new line. I can type almost all of the next line before the box expands for me to be able to see it. It's also taking a long time to respond to enter or the plus symbol to make a new box.

To Reproduce Steps to reproduce the behavior:

1. Go to edit a new post in the app
2. Type a few lines using the Paragraph Block.
3. Notice that after a few lines the next line starts to disappear as you type then shows up when almost done with the next line.
4. Add a block by tapping Enter after a Paragraph block.
5. Notice it takes some time for the next block to be added.

Expected behavior

I would expect to see all my text as I type it. I was able to replicate the original issue. While testing I noticed it did not lag when I dictated text. Only when I typed.

Screenshots

There is a screencast on https://www.youtube.com/watch?v=ZfM_Oq-BY5E (used with the customer's permission). This is from #5187204-zen

Smartphone (please complete the following information):

• Device: Android
• Version 10

[SiobhyB]

@ChrissiePollock, thank you for reporting this! 🙇‍♀️

What version of the app were you able to replicate this on, out of interest? I ask because I noticed the user is on 19.6 and a performance improvement was introduced in the upcoming 19.8 (available internally, but scheduled to be available from the App Store on May 16th). It'd be interesting to know if you're able to replicate with 19.8 installed or if you see any improvement in the time it takes for new blocks to load with that version.

I also haven't been able to replicate this on my Pixel 6 (Android 12) and wanted to make a note of the devices where this has been replicated, in case the older OS used by these devices are of importance in debugging this:

• User's device: Samsung SM-A115U, currently comes with Android 10 (11 in some regions)
• Chrissie's device: Galaxy S7, Android 10 (please feel welcome to correct if wrong!)

[ChrissiePollock]

Sorry. I didn't see this mention @SiobhyB. I don't remember what version I was on. I just tested again, and it doesn't seem as problematic as it was back then, but I can still see a lag and lose typing for about half a line before things catch up and let me see. My current version is 20.2-rc-1 (1239). You are correct on my device info.

[SiobhyB]

I'm going to remove the [Pri] High label, given the difficulty reproducing and the suspicion that this is an issue with older sites. As it's been a couple of years since this report, also, there's a chance improvements to the editor over that time period have had a positive impact.

I also wanted to x-reference some other open performance-related issues that are relevant: https://github.com/wordpress-mobile/gutenberg-mobile/issues/2594, https://github.com/wordpress-mobile/gutenberg-mobile/issues/2628, https://github.com/wordpress-mobile/gutenberg-mobile/issues/1978, https://github.com/wordpress-mobile/gutenberg-mobile/issues/1888. It may be possible to close some of these and group them into one issue.