1425603 - Add a test for obeying overscroll-behavior when scrolling over a checkerboarded area

Status: RESOLVED FIXED

(Core :: Panning and Zooming, defect, P3)

Description

[Botond Ballo [:botond]]

Attachment: Testcase

STR:
  1. Load the attached testcase
  2. Scroll over or click on the scrollable <div>
     to cause it to be layerized.
  3. Scroll over the <div> quickly until checkerboarding
     is triggered, and then continue scrolling over the
     checkerboarded area until you reach the bottom and
     then some more.

Expected results:
  overscroll-behavior is obeyed (the scroll is not handed
  off to the page).

Actual results:
  Sometimes, the scroll is handed off to the page.

Comment 1

[Botond Ballo [:botond]]

This may be related to bug 1307555.

Comment 2

[Botond Ballo [:botond]]

(In reply to Botond Ballo [:botond] from comment #1)
> This may be related to bug 1307555.

I'm seeing wheel scrolls over checkerboarded areas consistently hitting the enclosing scroll frame (I assume due to bug 1307555), but only intermittently triggering scrolling of it.

Comment 3

[Botond Ballo [:botond]]

(In reply to Botond Ballo [:botond] from comment #2)
> I'm seeing wheel scrolls over checkerboarded areas consistently hitting the
> enclosing scroll frame (I assume due to bug 1307555), but only
> intermittently triggering scrolling of it.

That appears to be due to wheel transactions: hitting the enclosing scroll frame only results in scrolling it if the event is not added to the existing wheel transaction for the subframe. This happens if the mouse is moved since the last scroll (or if the wheel transaction timeout is reached, but that's unlikely since chances are we don't checkerboard that long).

Indeed, that gives rise to the following, more reliable STR for this bug:

STR:
  1. Load the attached testcase
  2. Scroll over or click on the scrollable <div>
     to cause it to be layerized.
  3. Scroll over the <div> quickly until checkerboarding
     is triggered.
  4. While checkerboarding, move the mouse, still
     keeping it within the <div> and over the
     checkerboarded area, and quickly scroll again.

Given this diagnosis, I don't see a way to fix this bug without fixing the underlying bug 1307555.

Comment 4

[Botond Ballo [:botond]]

I've confirmed that the patch in bug 1307555 fixes this. We may still want to add a testcase specific to overscroll-behavior in this bug.

Comment 5

[Botond Ballo [:botond]]

(In reply to Botond Ballo [:botond] from comment #4)
> I've confirmed that the patch in bug 1307555 fixes this. We may still want
> to add a testcase specific to overscroll-behavior in this bug.

I'm working on a test.

Comment 6

[Botond Ballo [:botond]]

Attachment: Bug 1425603 - APZ mochitest for obeying overscroll-behavior when scrolling over a checkerboarded area.

Review commit: https://reviewboard.mozilla.org/r/230832/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/230832/

Comment 7

[Botond Ballo [:botond]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=12465658bde148ec0f42d30dd509a7db4bf2415f

Comment 8

[Kartikaya Gupta (email:[e-mail])]

Comment on attachment 8961987 [details]
Bug 1425603 - APZ mochitest for obeying overscroll-behavior when scrolling over a checkerboarded area.

https://reviewboard.mozilla.org/r/230832/#review236344

There's some trailing whitespace in the test file, but otherwise looks good!

Comment 9

[Botond Ballo [:botond]]

Comment on attachment 8961987 [details]
Bug 1425603 - APZ mochitest for obeying overscroll-behavior when scrolling over a checkerboarded area.

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/230832/diff/1-2/

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f8d06bbeaf8e
APZ mochitest for obeying overscroll-behavior when scrolling over a checkerboarded area. r=kats

Comment 11

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/f8d06bbeaf8e

Comment 12

[Botond Ballo [:botond]]

The actual fix for this scenario landed in 60, in bug 1307555. The only thing that landed here is a test, and I don't think we need to uplift that to 60.