1494685 - Text on payun-payun parallax page disappears when it isn't fully in the viewport

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P2)

Description

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

Go to https://belen-albeza.github.io/scroll-demos/parallax.html and start scrolling down. Observe the text-shadow on the "Payun-payun" header. As soon as the bounding box for that element hits the edge of the viewport the text shadow disappears.

I can reproduce on macOS and Windows. Happens even with APZ off.

Comment 1

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

Also related: the airplane that scrolls up from the bottom also disappears as soon as it encounters the edge of the viewport instead of getting clipped properly.

Comment 2

[Markus Stange [:mstange]]

This sounds similar to the problem reported in this comment on github: https://github.com/servo/webrender/issues/3087#issuecomment-423595274

It seems that whenever 3d transformed elements are not visible in their entirety, we paint the wrong parts of the contents.

Comment 3

[Mayank Bansal]

(In reply to Kartikaya Gupta (email:[e-mail]) from comment #1)
> Also related: the airplane that scrolls up from the bottom also disappears
> as soon as it encounters the edge of the viewport instead of getting clipped
> properly.

As of today, the airplane disappears, but some part of it is drawn in the tab-bar. 
Please see the screenshot attached

Comment 4

[Mayank Bansal]

Attachment: bug.png

see at the top of the tab-bar

Comment 5

[Emilio Cobos Álvarez (:emilio)]

The airplane looks fine now, it's only text what disappears.

Comment 6

[Emilio Cobos Álvarez (:emilio)]

AFAICS it's only text (shadows remain there correctly) and it's not only the header (other text like the "(Psttt… that browser is Firefox.)" also disappears.

Comment 7

[Emilio Cobos Álvarez (:emilio)]

I'll take a look.

Comment 8

[Emilio Cobos Álvarez (:emilio)]

Attachment: Reduced (comment out text-indent to hide the text).

Comment 9

[Emilio Cobos Álvarez (:emilio)]

Attachment: Add a reftest.

Probably not the most reliable test to catch this (as it depends on
the font and such) but still fails here and I'd like WPT to have a test-case
for this. I'm looking into adding a WR test-case ATM, though fighting with
it way too much.

Comment 10

[Emilio Cobos Álvarez (:emilio)]

Attachment: GitHub Pull Request

Still got to find a more reliable test-case for WR.

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d44ae1668a70
Add a reftest. r=kats

Comment 12

[Pulsebot]

Backout by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3c25a0b6d269
Backed out changeset d44ae1668a70 as per emilio's request.

Comment 13

[Cristian Brindusan [:cbrindusan]]

Please note that a wpt linting failure was present on your push:
https://treeherder.mozilla.org/logviewer.html#?job_id=204981680&repo=autoland&lineNumber=258

Comment 14

[Emilio Cobos Álvarez (:emilio)]

That is a linter bug, about:blank is a perfectly valid reference.

Comment 15

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/13487 for changes under testing/web-platform/tests

Comment 16

[James Graham [:jgraham]]

Hmm, this was supposed to be fixed by https://github.com/web-platform-tests/wpt/pull/9421; I'll check what's going on.

Comment 17

[James Graham [:jgraham]]

https://github.com/web-platform-tests/wpt/pull/13489

Comment 18

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR was closed without merging

Comment 19

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Can't merge web-platform-tests PR due to failing upstream checks:
Github PR https://github.com/web-platform-tests/wpt/pull/13487
* continuous-integration/travis-ci/pr (https://travis-ci.org/web-platform-tests/wpt/builds/440625751?utm_source=github_status&utm_medium=notification)

Comment 20

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/2d5c8e9ca5a3
Add a reftest. r=kats

Comment 21

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Can't merge web-platform-tests PR due to failing upstream checks:
Github PR https://github.com/web-platform-tests/wpt/pull/13487
* continuous-integration/travis-ci/pr (https://travis-ci.org/web-platform-tests/wpt/builds/448101101?utm_source=github_status&utm_medium=notification)

Comment 22

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream web-platform-tests status checks passed, PR will merge once commit reaches central.

Comment 23

[Raul Gurzau (:RaulG)]

https://hg.mozilla.org/mozilla-central/rev/2d5c8e9ca5a3

Comment 24

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged

Comment 25

[Ryan VanderMeulen [:RyanVM]]

Is this something we should consider backporting to Beta for the experiments running there or can this just ride the 65 train?

Comment 26

[Emilio Cobos Álvarez (:emilio)]

I think the fix landed on beta, given https://github.com/servo/webrender/pull/3187 landed 20 days ago.

Comment 27

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-beta/rev/fa0dfb7abb5e