1449976 - [WebRender enabled] text-shadow is wrongly shown on clipped text

Status: VERIFIED FIXED

(Core :: Graphics: WebRender, defect, P1)

Description

[Fanolian]

Attachment: Text shadow wrongly shown on clipped text with WR on

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:61.0) Gecko/20100101 Firefox/61.0
Build ID: 20180329100042

Steps to reproduce:

1. Sign in to Gmail.
2. Go to Gmail's Settings > General.
3. Enable "Show snippets - Show snippets of the message (like Google web search!)" . The option is near the bottom.
4. Go to Inbox or All Mail, which shows a list of email and some of the email content (snippets).

5. Turn on devtool's Inspector on the page.
6. Add the following rule in the Rules panel on the right, to set text-shadows on all text:
* { text-shadow: 1px 1px; }
7. Observe the snippets


Actual results:

Text shadow is showing on clipped snippets, overlapping the date, and extending towards the right end of the page.
(Please see the attached screenshot.)


Expected results:

With WebRender is off, text shadow is not shown on those clipped text.

Comment 1

[Fanolian]

Attachment: Expected text shadow, with WR off

Comment 2

[Fanolian]

Attachment: Text shadow in Inoreader

I found another example on https://www.inoreader.com. The line the top red arrow is pointing to is merely text shadows for the clipped content

The issue on this site, however, is seemingly affects only CJK characters. I do not see such extra text shadows for English content in a similar setting.

Comment 3

[Fanolian]

Interestingly, I am _not_ able to capture the bugged parts of text-shadow using Nightly's "Take a Screenshot" feature.
I can see the bugged text-shadow. I can select the relevant regions using the Screenshot feature. But when I save the screenshot locally and open it with various image viewing software, the bugged part is gone from the image file! Somehow the bugged text shadow is bypassing the Screenshot feature...

p.s. The attached screenshots in previous comments are taken with Windows' Snipping Tool.

Comment 4

[Aria Beingessner [:Gankra]]

I believe the screenshot thing is just because the Take A Screenshot feature doesn't use webrender (same as printing and a few other things).

Comment 5

[Aria Beingessner [:Gankra]]

Confirmed I can see this on windows 10 (not on mac though).

Comment 6

[Aria Beingessner [:Gankra]]

STR: 

data:text/html,<div style="width: 3em; text-overflow: clip; overflow: hidden;text-shadow: 1px 1px black; white-space: nowrap;color: red;">overflow text</div>

Comment 7

[Darkspirit]

try builds from bug 1447998 comment 7:
> WR @ 53750b8b
mozregression --repo try --launch 12aae4a8f4d67ff0d3549465d0b9f1479825914b --pref gfx.webrender.all:true startup.homepage_welcome_url:"data:text/html,<div style='width: 3em; text-overflow: clip; overflow: hidden;text-shadow: 1px 1px black; white-space: nowrap;color: red;'>overflow text</div>"
good

> WR @ 097bc025ccc85fad7891d3422d2bccefc0e42948
mozregression --repo try --launch b083a08fc957f9c90d6e963b1fc95567a96f5710 --pref gfx.webrender.all:true startup.homepage_welcome_url:"data:text/html,<div style='width: 3em; text-overflow: clip; overflow: hidden;text-shadow: 1px 1px black; white-space: nowrap;color: red;'>overflow text</div>"
bad

Regression range: https://github.com/servo/webrender/compare/53750b8b5760a9e63414ae486de7249cd49ac700...097bc025ccc85fad7891d3422d2bccefc0e42948

Comment 8

[Aria Beingessner [:Gankra]]

Wait ok my STR works on mac too (which is a relief since the issue should be platform independent), I'm not sure why I couldn't see it in gmail on macos :S

Comment 9

[Alice0775 White]

Attachment: a testcase html

Comment 10

[Aria Beingessner [:Gankra]]

fixed upstream, needs a test in gecko

Comment 11

[Aria Beingessner [:Gankra]]

Attachment: Bug 1449976 - add regression test for fast-shadow clipping.

Still waiting for wr update, but here's the test.

Comment 13

[Aria Beingessner [:Gankra]]

Fixed merged into gecko, test can land now.

Comment 14

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/c880e315c1b3
Add regression test for fast-shadow clipping. r=jrmuizel

Comment 15

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/cf994f4482ab
Add fuzz for OSX and Windows. r=me

Comment 16

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/5d2002c31762
Add a pinch more fuzz on Windows. r=me

Comment 17

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/c880e315c1b3
https://hg.mozilla.org/mozilla-central/rev/cf994f4482ab
https://hg.mozilla.org/mozilla-central/rev/5d2002c31762

Comment 18

[Fanolian]

I can verify the issue is fixed by bug 1449562 in Nightly. Thanks.