1244482 - Text underlined by "Check Spelling" significantly reduce performance for the first 5 seconds after I focus textarea

Status: NEW

(Core :: Spelling checker, defect)

Description

[arni2033]

Attachment: testcase 1 - Text underlined by 'Check Spelling' significantly reduce performance.htm

>>>   My Info:   Win7_64, Nightly 46, 32bit, ID 20160129030206
STR:
1. Open attached "testcase 1", make sure there's no scrollbar in textarea.
2. Click in textarea to cancel all text selection, make sure that all text is underlined with red.
3. Click outside of textarea and scroll page to the beginning. Wait 3 seconds.
4. Hover mouse over the center of visible part of textarea
5.A) Hold left mouse button and immediately start moving mouse pointer within textarea
     Keep moving mouse pointer for 10 seconds
5.B) Hold middle mouse button (wheel) and start autoscrolling the page. But you shouldn't let
     textarea completely leave the viewport (to observe how the page actually lags).
     Keep autoscrolling for 10 seconds
     
AR:  Text selection/page scrolling lags for first 5 seconds of Step 5. Then all lags disappear.
ER:  There should be no lagging in step 5 at all.

Notes:
 (B) will will be "fixed" by enabling APZ for autoscrolling (presumably). I think so because I
first encountered this on Dev.Edition, and scrolling "by 1 page" was also affected, and now it's not
 
 Well, there's a story behind this bug. I noticed it on Bugzilla a long time ago, but when I checked
the same page on Nighly, there were no bugs. Now I know exactly that it was caused by (sic!) english
words in my bugreport underlined by Spell Checker, because there's no such words in russian language.

 I _always_ try to avoid scrollbars in textarea, and I also often use autoscrolling,
so this bug basically _always_ happens to me, at least on Bugzilla.

Comment 1

[arni2033]

This was caused by bug 1205983. Regression range:
> https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=4f2620f7822d6929f57f90c456e24910a76ad933&tochange=ee7ec0b2d382f4a0e60ee5c3e5cac5701fccffc2

Comment 2

[Jorg K (CEST = GMT+2)]

I don't experience any lag in my freshly installed FF 44. Perhaps I misunderstood the STR.

Comment 3

[arni2033]

(In reply to Jorg K (GMT+1) from comment #2)
> I don't experience any lag in my freshly installed FF 44.
1) What about Nightly?
2) Do you see how lag ends on this screencast?
This is way more noticeable if you actually follow STR yourself, not watch the video.
> screencast   https://dl.dropboxusercontent.com/s/lpgxt0ijgevohbe/bug%201244482%20comment%203.webm

Comment 4

[arni2033]

Any success reproducing this bug on Windows?

Comment 5

[Jorg K (CEST = GMT+2)]

OK, I can see it now, at least in case (A): Click and hold while moving the mouse. Text gets selected and shown in selection colour. During the first few seconds this is not really smooth, later it becomes smoother.

Comment 6

[Jim Mathies [:jimm]]

arni, can you reproduce in non-e10s?

Comment 7

[arni2033]

Yeah, non-e10s is affected.

Comment 8

[arni2033]

>>>   My Info:   Win7_64, Nightly 51, 32bit, ID 20160913030425 (2016-09-13)
Reproducible.

Comment 9

[David Bolter [:davidb] (NeedInfo me for attention)]

Too late for 49 unfortunately.

Comment 10

[Ritu Kothari (:ritu) (Inactive, please n-i to RyanVM, jcristau, or pascal)]

This seems related to bug 1303749.