1395127 - Inconsistent drawing behavior with canvas arc

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Tommy Knudsen]

Attachment: Firefox 54-57 screenshots

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:55.0) Gecko/20100101 Firefox/55.0
Build ID: 20170816204344

Steps to reproduce:

Draw a circle slice with a radius of 300px from 3.38rad to 3.80rad clockwise.

Minimal reproduction: https://jsfiddle.net/4rpo2t10/ 
A more complex example that shows multiple drawing errors: https://jsfiddle.net/L1xg2gzg/11/

If the radius is changed from 300px to 301px or 299px the slice is drawn correctly.

Tested as working on version 54
Tested as not working in safe mode on version 55.0.2
Tested as not working on version 56b7 and 57 nightly
All tests done on Ubuntu 17.04

Attached are screenshots of rendering of the complex example on Firefox 54,55,56b7,57n.


Actual results:

The slice is cut off at the top.


Expected results:

The slice should look like the slice from 1.38rad to 1.80rad in the minimal reproduction.

Comment 1

[Tommy Knudsen]

Sorry forgot to update minimal reproduction with the second slice, can be found here https://jsfiddle.net/4rpo2t10/1.

Comment 2

[Alice0775 White]

I can reproduce the problem on Windows10 if HWA is disabled.

Comment 3

[Alice0775 White]

Regression window:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=e6daa01f4c3ca434da646e1329cb9795b71539d4&tochange=e06077091df1f2577a052b43e86135cc12e87a4c

Regressed by: Bug 1340627


@:lsalzman
Your patch seems to cause the problem. Can you look this?

Comment 4

[Lee Salzman [:lsalzman]]

Attachment: fix Skia's AAA to work with even rounding

Narrowed this down to our silly even rounding modification to Skia. When they introduced analytic AA, they did not introduce codepaths for the even rounding case, as Skia upstream does not test with even rounding at all.

Also some fuzz tweaks for slight rendering differences resulting from this fix.

Comment 5

[Lee Salzman [:lsalzman]]

Upstream Skia bug report: https://skia-review.googlesource.com/c/skia/+/42520

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/24aaf120e7a9
fix Skia's AAA to work with even rounding. r=jrmuizel

Comment 7

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/24aaf120e7a9

Comment 8

[Ryan VanderMeulen [:RyanVM]]

Please request Beta approval on this when you get a chance.

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/67281ccb998f
adjust fuzz in layout/reftests/backgrounds/attachment-local-clipping-image-6.html. r=mchang

Comment 10

[Lee Salzman [:lsalzman]]

Comment on attachment 8904639 [details] [diff] [review]
fix Skia's AAA to work with even rounding

Approval Request Comment
[Feature/Bug causing the regression]: bug 1340627
[User impact if declined]: Broken rendering of curves when using the Skia content backend (all platforms except Windows + HWA).
[Is this code covered by automated tests?]: yes
[Has the fix been verified in Nightly?]: yes
[Needs manual test from QE? If yes, steps to reproduce]: no 
[List of other uplifts needed for the feature/fix]:
[Is the change risky?]: Low risk
[Why is the change risky/not risky?]: Small change to ensure that path coordinates are rounded in a way that is consistent with our previous long-standing rounding mode modification to Skia. The breakage occurred because Skia upstream introduced code that was not consistent with aforementioned modification.
[String changes made/needed]: none

Comment 11

[Lee Salzman [:lsalzman]]

(In reply to Pulsebot from comment #9)
> Pushed by [e-mail]:
> https://hg.mozilla.org/integration/mozilla-inbound/rev/67281ccb998f
> adjust fuzz in
> layout/reftests/backgrounds/attachment-local-clipping-image-6.html. r=mchang

Oops, that was supposed to be committed under bug 1366152. Backed out and recommitted that under correct bug number.

Comment 12

[Pulsebot]

Backout by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/22446487eed3
Backed out changeset 67281ccb998f for incorrect bug number. r=backout

Comment 13

[Liz Henry (:lizzard)]

Comment on attachment 8904639 [details] [diff] [review]
fix Skia's AAA to work with even rounding

Fix for graphics crash, verified in nightly, please uplift for beta 11

Comment 14

[Ryan VanderMeulen [:RyanVM]]

Bah, I uplifted this yesterday but forgot to mark the bug afterward. This made it in for b11.
https://hg.mozilla.org/releases/mozilla-beta/rev/59563d7fc7b6