1892653 - repeating-linear-gradient doesn't repeat when it contains OKLCH colors

Status: RESOLVED FIXED

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

Description

[Sage Fennel]

Attachment: repeating-linear-gradient_bug.html

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:126.0) Gecko/20100101 Firefox/126.0

Steps to reproduce:

Visit the attached HTML page with a CSS repeating-linear-gradient using OKLCH colors

Actual results:

In Firefox 126 and 127, the repeating-linear-gradient doesn't repeat when it contains OKLCH, OKLAB, LCH, or LAB colors

Named colors, HSL, and hex colors all seem to work fine

Expected results:

The repeating gradient should repeat

Comment 1

[Sage Fennel]

Attachment: Working gradient from Firefox 125

Comment 2

[Sage Fennel]

Attachment: Failing repeating-linear-gradient from Firefox 126

I noticed that the built-in screenshot tool in Firefox (Ctrl-Shift-S) actually doesn't reproduce the bug with the gradient... I have to use Windows 11 built-in screenshot tool (Win-Shift-S) in order to capture it correctly.

Maybe that would be useful for helping to figure out where the gradient render is failing.

Comment 3

[Alice0775 White]

I can reproduce the issue on Nightly127.0a1 Windows11.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=c4be4674be1b97309e8fd79c9787dbaeebf4cb56&tochange=a65ef2dc959b5fe431d3fcaa757b423aeec2677b

Comment 4

[BugBot [:suhaib / :marco/ :calixte]]

:ahale, since you are the author of the regressor, bug 1885716, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 5

[Donal Meehan [:dmeehan]]

:gw pinging as triage owner, could this be triaged for severity?
Next week is the final week of beta for Fx126 so we don't have long left for fixes.

Comment 6

[Ashley Hale [:ahale]]

I'll look into this tomorrow, I am not sure how repeating gradients interact with the hue longer fix I made in bug 1885716, so I'll need to try out these test cases - speaking of which, we don't appear to have test coverage for this case, so I'll make a WPT test as part of fixing this (like how I made a WPT test for hue longer).

Comment 7

[Donal Meehan [:dmeehan]]

Tracking since this is was triaged as an S2

Comment 8

[Ashley Hale [:ahale]]

I wasn't able to make much progress on this today but I will get a fix ready over the weekend.

Comment 9

[Ashley Hale [:ahale]]

Attachment: Bug 1892653 - Add WPT test for repeating gradients in HSL and OKLCH spaces r?#gfx-reviewers

Comment 10

[Ashley Hale [:ahale]]

Adding a WPT test first before I fix the code.

Comment 11

[Ashley Hale [:ahale]]

Attachment: Bug 1892653 - Fix repeating gradient truncation on oklch color space r?#gfx-reviewers

Comment 12

[Ashley Hale [:ahale]]

In terms of minimally invasive fixes, this should address the problem, however it would be good to check if it is a non-repeating gradient as well, because this logic could still misbehave on a repeating gradient with longer hue interpolation, I expect that to be a far more obscure issue in terms of user impact.

Comment 13

[Ashley Hale [:ahale]]

Attachment: Bug 1892653 - Fix repeating oklch gradients r?#gfx-reviewers

Comment 14

[Ashley Hale [:ahale]]

Third patch fixes the one remaining corner case (CSS repeating gradient with longer hue), which is probably rare, but now the logic always does what it is meant to do.

Comment 15

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3e212a42ac4d
Fix repeating oklch gradients r=gfx-reviewers,lsalzman

Comment 16

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

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/45975 for changes under testing/web-platform/tests

Comment 17

[tszentpeteri]

https://hg.mozilla.org/mozilla-central/rev/3e212a42ac4d

Comment 18

[BugBot [:suhaib / :marco/ :calixte]]

The patch landed in nightly and beta is affected.
:ahale, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
• If no, please set status-firefox126 to wontfix.

For more information, please visit BugBot documentation.

Comment 19

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

Upstream PR merged by moz-wptsync-bot

Comment 20

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

Upstream PR merged by moz-wptsync-bot

Comment 21

[Ashley Hale [:ahale]]

Attachment: Nightly after fix

Looks like the fix has landed in nightly. Will request uplift on it.

Comment 22

[Ashley Hale [:ahale]]

Comment on attachment 9399274 [details]
Bug 1892653 - Fix repeating oklch gradients r?#gfx-reviewers

Beta/Release Uplift Approval Request

• User impact if declined: CSS gradients that are repeating type do not work in non-sRGB colorspaces, such as HSL and OKLCH. Non-repeating ones look fine. Repeating gradients are mostly used to make stripe patterns on web pages, sometimes as a background fill, though it is not clear how often they are in non-sRGB colorspaces.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce: View first attachment https://bugzilla.mozilla.org/attachment.cgi?id=9397785 , before the fix there is only a single stripe at the top of each example, after the fix it correctly looks like a stripe pattern with alternating color stripes on each of the two examples.
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Simplified logic that should be more robust, only a single very specific case that will use the gradient extending logic (the one case it was meant to fix - longer hue on a non-repeating gradient such as OKLCH space).
• String changes made/needed:
• Is Android affected?: Yes

Comment 23

[Donal Meehan [:dmeehan]]

Comment on attachment 9399274 [details]
Bug 1892653 - Fix repeating oklch gradients r?#gfx-reviewers

Approved for 126.0b9

Comment 24

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/c64dbda3f942