303364 - Scrolling (with the mouse wheel) over a textarea/textbox with the mousewheel is slow

Status: RESOLVED WORKSFORME

(Core :: Widget, defect)

Description

[Caleb]

It seems that when you scroll the page with the mousewheel and your mouse hovers
a textarea/textbox (the mouse changes from the normal icon to the text select
icon and then back) the CPU usage jumps wildly and there is noticable sluggishness.

This bug might be tricky to reproduce for some, but you can can easily see it if
you turn Smooth Scrolling on. (Although it happens with smooth scrolling set to
off aswell!).

Reproduction:

1. Open https://bugzilla.mozilla.org/show_bug.cgi?id=280769
2. Place your mouse above the "Target Milestone:" link so it's actually under
some of the textboxes below it (QA, URL, Summary, Whiteboard, Keywords).
3. Scroll the mouse up and down quickly without moving it. You should stop
scrolling down once the mouse reaches the Attachments table and then scroll back
up to the original position.

Repeat step (3) a couple of times and notice the slowdown. This slowdown only
happens when the mouse hovers textboxes/textareas, so if you try to scroll up
and down quickly on other parts of the page, you will not see anything slowing down.

Comment 1

[Aaron Slunt]

Confirmed Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8b4)
Gecko/20050803 Firefox/1.0+ ID:2005080306

Comment 2

[Adam Guthrie]

Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8b4) Gecko/20050804 Firefox/1.0+
ID:2005080414

I get the same CPU usage as I do when scrolling any other part of the page
rapidly Must be a Windows-only issue.

Comment 3

[Caleb]

I've had some hard time tracking the exact regression date, but I've pretty much
tracked it between 2005-01-19-13 (the bug does not happen) to 2005-01-31-07 (bug
is 100% reproducable).

It was hard narrowing down because some builds seem to be generally slower while
smooth scrolling than the other, but I think I've nailed it down to:

Works in:
2005-01-19-13
Broken in:
2005-01-20-11

Bonsai query:
http://bonsai.mozilla.org/cvsquery.cgi?treeid=default&module=PhoenixTinderbox&branch=HEAD&branchtype=match&dir=&file=&filetype=match&who=&whotype=match&sortby=Date&hours=2&date=explicit&mindate=2005-01-19&maxdate=2005-01-20&cvsroot=%2Fcvsroot

Comment 4

[Caleb]

I've just replaced my mouse. It seems that my precious mouse was using a
different way of mousewheel scrolling.

It scrolled probably 1 line at a time, but it also accelerated the faster you
scrolled, so this bug is very visible with it. But on my new mouse, that scrolls
just X lines at once (no accelerated/smoothing) it's not very noticable.

Comment 5

[Caleb]

(In reply to comment #4)
s/precious/previous 

Comment 6

[Caleb]

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a1) Gecko/20050911
Firefox/1.6a1

Hmm.. But I do get this at work.. Big time!

Scrolling over textareas, textboxes, combo boxes, checkboxes gives me CPU usage
spikes of up to 100%.

I've noticed one thing though, the slowdown is felt when the mouse is leaving
the broder of the element.

For example, if you scroll with the mousewheel, while the mouse is inside a
large textarea you won't feel any slowdowns, but if you scroll a bit more to the
bottom, so the mouse leaves the textarea you will notice CPU spikes.

Any clues ?

Comment 7

[Bogdan Maris, Desktop Test Engineering]

This is no longer a problem in actual builds like latest Nightly 25.0a1 (buildID: 20130721030203). Dropping the qawanted and marking this as WFM since this is a very old bug. If anyone thinks that differently please add the qawanted back and change the status of the bug.