514783 - Fast mousewheel scrolling moves me way too far, after bug 512235

Status: RESOLVED FIXED

(Core :: DOM: UI Events & Focus Handling, defect)

Description

[Daniel Holbert [:dholbert]]

Attachment: testcase 1

STEPS TO REPRODUCE:
 1. Load attached testcase, and position your cursor over the scroll box.
 2. Place your index finger on your mouse's scrollwheel, and *very slowly* scroll down as far as you can without removing your finger.
 3. Scroll back to the top
 4. Repeat step 2, but this time, scroll faster.

EXPECTED RESULTS:
 Step 4 should scroll you roughly the same distance that step 2 did.

ACTUAL RESULTS:
 Step 2 (slow scroll) leaves me with "30" at the top of the scrollbox, but Step 4 (fast scroll) leaves me with "200" at the top of the scrollbox.

This regressed in yesterday's nightly.
BROKEN:
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.3a1pre) Gecko/20090903 Minefield/3.7a1pre
WORKS:
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.3a1pre) Gecko/20090902 Minefield/3.7a1pre

HG regression range:
http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=75af94f85a98&tochange=3cab7a0c2c3d

Comment 1

[Daniel Holbert [:dholbert]]

More real-world steps to reproduce:
 1. Load attached testcase.
 2. Position your finger at the top of your mousewheel, and scroll down quickly.
 3. Without removing your finger, *slowly* scroll back up, so that your finger returns to its original position.

EXPECTED RESULT: I should end up at my original scroll-position.
ACTUAL RESULT: I end up about 100 lines below my original scroll-position.

Comment 2

[Daniel Holbert [:dholbert]]

Looks like changeset 7475d595c48a (Bug 512235) is the cause.  I guess this bug here is actually the desired behavior, though -- perhaps the acceleration is just too fast, as bug 512235 comment 14 suggests it might be?  (It certainly seems too fast to me.)

Updating this bug's summary.

Comment 3

[Daniel Holbert [:dholbert]]

It looks like I can restore the old behavior by setting the pref "mousewheel.acceleration.factor" to 1.  (Its default is currently "10".)

Comment 4

[Daniel Holbert [:dholbert]]

(In reply to comment #3)
> "mousewheel.acceleration.factor"
Looking at the patch, it looks like any negative value of that pref will restore the old behavior, too.

Comment 5

[Daniel Holbert [:dholbert]]

And the patch in bug 513817 disables acceleration by default, which would fix this bug (restore original behavior, by default).

Setting this bug to depend on that one (and removing bug 512235 from blocking field, so as to not create a circular dependency).

Comment 7

[Dão Gottwald [:dao]]

Oops! 515206 is a duplicate of this one.

Comment 9

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

fixed by bug 513817.