1448817 - Incorrect rendering of rotated elements with border-radius

Status: RESOLVED FIXED

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

Description

[Magne Andersson]

Attachment: testcase.html

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:61.0) Gecko/20100101 Firefox/61.0
Build ID: 20180325220121

Steps to reproduce:

With WebRender enabled in Firefox Nightly, elements with certain combinations of the rotate()-transform and border-radius render incorrectly. I have extracted the attached testcase based on code that I am currently working on.


Actual results:

When the elements have been rotated beyond a certain degree, their colours render slightly brighter than intended and surrounding box-shadows seem to leak through them. The issue does not appear when border-radius is removed.

Comment 1

[Magne Andersson]

Attachment: With WebRender (left), without WebRender (right)

Comment 2

[Darkspirit]

good = looks good, but is drawn on chrome when zooming in.
bad = transparent, but no longer drawn on chrome.

mozregression --good 2018-01-17 --bad 2018-03-25 --pref gfx.webrender.all:true startup.homepage_welcome_url:"https://bug1448817.bmoattachments.org/attachment.cgi?id=8962286"
> 10:27.09 INFO: Last good revision: d49f13abd54ad351ee1665a639127f14b938bc25
> 10:27.09 INFO: First bad revision: 5eb19c81c7fd7d5ffbc3eac211cf20136c02c3d7
> 10:27.09 INFO: Pushlog:
> https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=d49f13abd54ad351ee1665a639127f14b938bc25&tochange=5eb19c81c7fd7d5ffbc3eac211cf20136c02c3d7

> 5eb19c81c7fd	Kartikaya Gupta — Bug 1439565 - Update reftest annotations for changes in WR PR 2445. r=jrmuizel
> 3a32ca63e380	Kartikaya Gupta — Bug 1439565 - Update webrender to commit 8a19316a733a484bf9bafb8257e3008b1418bfe4. r=jrmuizel

Try builds are gone.
https://github.com/servo/webrender/compare/e8d2ffb404a85651fe08a6d09abbece9bd2b9182...8a19316a733a484bf9bafb8257e3008b1418bfe4

Comment 3

[Milan Sreckovic [:milan] (needinfo for best results)]

This appears to be due to Patrick's pathfinder change?

Comment 4

[Glenn Watson [:gw]]

The PathFinder code hasn't landed in Gecko (or WR) yet, so it won't be that.

Comment 5

[Glenn Watson [:gw]]

Oh, I think I may have misinterpreted your comment, sorry. I thought you were referring to the currently open Pathfinder integration PR. Indeed, it does appear to be related to the anti-aliasing algorithm change that Patrick added.

I'll try to create a reduced wrench test case for Patrick to take a look at.

Comment 6

[Glenn Watson [:gw]]

WR issue with reduced wrench test case: https://github.com/servo/webrender/issues/2576

Comment 7

[Glenn Watson [:gw]]

This will be fixed when https://github.com/servo/webrender/pull/2604 lands in WR/Gecko.