1731165 - Typing multiple spaces on an empty input element is slow/unresponsive

Status: VERIFIED FIXED

(Core :: Layout, defect, P2)

Description

[Robert Marcano]

User Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:92.0) Gecko/20100101 Firefox/92.0

Steps to reproduce:

1- Open a web page with an input element, like the MDN input example:

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input

or any input element inside the Firefox UI (the dedicated search field on the toolbar)

2- Focus on the input element and type spaces multiple times, fast, or let the key pressed in order to repeat the spaces.
3- Empty the field and now type a letter and the repeat typing multiple spaces

Actual results:

When the input field is empty at step 2, spaces added slowly, like an unresponsive UI busy processing events.

At step 3, when the field contents start with a letter, spaces are added fast as expected

Expected results:

Step 2 and 3 should be both responsive and fast.

Tested with and version 90 Firefox developer edition build I still haven't updated and the space typing speed was fine. With Firefox 92, is slow even on a new empty profile. It looks like a regression from 90 or 91.

Comment 1

[Alice0775 White]

I can reproduce the issue on Nightly94.0a1 Windows10.
Keep holding keydown `Space Bar' does not update caret position smoothly.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=f6410b337e8aa34545ae5545ec7b49d1aa706e5d&tochange=ccc6e271d9dbd7bbb3b0c640ff267cb6120322a9

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Well, it's not a perf thing. It's not "slow" as in using a lot of CPU, it seems we're just not repainting the caret properly. Will look, thanks!

Comment 3

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1731165 - Invalidate the right frame from nsCaret::SchedulePaint when we paint the caret from the containing block. r=mats,miko

Not sure how easy it is to come up with a test-case for this, will try
though.

Comment 4

[Emilio Cobos Álvarez (:emilio)]

Changing severity to S3 because it's a small-ish issue, and an old regression.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/340719f2946c
Invalidate the right frame from nsCaret::SchedulePaint when we paint the caret from the containing block. r=miko

Comment 6

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/340719f2946c

Comment 7

[BugBot [:suhaib / :marco/ :calixte]]

The patch landed in nightly and beta is affected.
:emilio, is this bug important enough to require an uplift?
If not please set status_beta to wontfix.

For more information, please visit auto_nag documentation.

Comment 8

[Giorgia Nichita, Release Desktop QA]

Reproduced this on macOS 10.15 on an affected Nightly build 95.0a1 (20210916094303) following the steps from comment 0.

Verified as fixed on Beta 95.0b2 (20211102190739), across following platforms: Win 10x64, macOS 10.15 and Ubuntu 20.04. Space typing response time is correct.