Issue 128537 in chromium: Touch fling on gmail often jumps too far

[chro...@googlecode.com]

Status: Assigned
Owner: sad...@chromium.org
CC: wjmacl...@chromium.org, rjkr...@chromium.org
Labels: Type-Bug Pri-1 Area-UI Feature-Ash-Gestures Hotlist-Link OS-Chrome
MStone-21

New issue 128537 by rby...@chromium.org: Touch fling on gmail often jumps
too far
http://code.google.com/p/chromium/issues/detail?id=128537

Google Chrome 21.0.1137.5 (Official Build 137304) canary
Platform 2299.0.0 (Official Build) canary-channel link
WebKit 537.1 (@117068)

What steps will reproduce the problem?
1. Open a long thread in gmail
2. Fling on a touch screen up and down and watch the scroll bar
3. Position the thread near (but not at) the top and fling up

What is the expected output? What do you see instead?
Expect the scrollbar to move smoothly, expect to see animation scrolling up.
Instead the scrollbar often starts with a big jump and when near the top of
the thread fling up immediately jumps to the top rather than animating
there smoothly.

In contrast, trackpad fling works fine.

Note that I can repro this using several different touch screens - it
doesn't appear related to any issue with noisy touch events.

In issue 120154 sadrul said:
rjkroege@ said this happens because from the touch-screen fling, webkit
does some scrolling and also generates JS scroll events, and gmail probably
handles the JS scroll events to do its own scrolling, so we end up with too
much velocity. I do not know how difficult it is to fix this case.

Can we produce a simple repro that validates this is the problem? Why
isn't it a problem for trackpad? Eg. is the JS eating mousewheel events
indicating it's doing it's own scrolling but not eating the corresponding
touch events?

[chro...@googlecode.com]

Issue 128537: Touch fling on gmail often jumps too far
http://code.google.com/p/chromium/issues/detail?id=128537

This issue is no longer blocking issue 120154.
See http://code.google.com/p/chromium/issues/detail?id=120154
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[chro...@googlecode.com]

Comment #1 on issue 128537 by rby...@chromium.org: Touch fling on gmail

often jumps too far
http://code.google.com/p/chromium/issues/detail?id=128537

Is it possible this is just the software scrolling performance issues?
I.e. we are actually scrolling smoothly but not painting the first frame
for > 200ms or so?

[chro...@googlecode.com]

Updates:
Owner: rjkr...@chromium.org

Comment #2 on issue 128537 by rjkr...@chromium.org: Touch fling on gmail

often jumps too far
http://code.google.com/p/chromium/issues/detail?id=128537

the touchpad and touchscreen scroll code have identical paint paths and
should have identical performance.

the scrollbar is painted asynchronously and can always be laggy.

I'll investigate.

[chro...@googlecode.com]

Updates:
Status: Started

Comment #3 on issue 128537 by rjkr...@chromium.org: Touch fling on gmail

often jumps too far
http://code.google.com/p/chromium/issues/detail?id=128537

(No comment was entered for this change.)

[chro...@googlecode.com]

Comment #5 on issue 128537 by bugdro...@chromium.org: Touch fling on gmail
often jumps too far
http://code.google.com/p/chromium/issues/detail?id=128537#c5

The following revision refers to this bug:
http://src.chromium.org/viewvc/chrome?view=rev&revision=139943

------------------------------------------------------------------------
r139943 | rjkr...@chromium.org | Thu May 31 18:08:49 PDT 2012

Changed paths:
M
http://src.chromium.org/viewvc/chrome/trunk/src/ui/aura/gestures/gesture_recognizer_unittest.cc?r1=139943&r2=139942&pathrev=139943
M
http://src.chromium.org/viewvc/chrome/trunk/src/ui/base/gestures/gesture_sequence.cc?r1=139943&r2=139942&pathrev=139943

GestureScrollEnd event had non-zero velocity causing overscroll on software
fling path.

GestureScrollEnd (indicating the end of a touchscreen interactive scrolling
gesture) contained velocity. This was causing an additional scroll at the
start of
a touchscreen-initiated fling.

BUG=128537
TEST=by hand


Review URL: https://chromiumcodereview.appspot.com/10446103
------------------------------------------------------------------------

[chro...@googlecode.com]

Updates:
Status: Fixed

Comment #6 on issue 128537 by rjkr...@chromium.org: Touch fling on gmail
often jumps too far