Intent to implement: CSS conic-gradient

[Tim Nguyen]

Summary: CSS conic-gradients allow developers to specify gradients that
start from a certain angle where color stops are placed around the
circumference of a circle centered around a specified point.

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=conic-gradients

Standard: https://drafts.csswg.org/css-images-4/#conic-gradients

Target Release: 75-76

Platform coverage: All, initially WebRender only (though it shouldn't be
long until it's implemented for other backends)

Preference behind which this will be implemented:
layout.css.conic-gradient.enabled,
turned off by default until it's implemented outside of WebRender

DevTools bug: n/a, devtools could potentially add a gradient editor, but
that's also applicable to linear/radial gradients

Other browsers: shipped since Chrome 69, Safari 12.1, Edge 79 and Opera 64

web-platform-tests:
https://searchfox.org/mozilla-central/search?q=conic-gradient&case=false&regexp=false&path=testing%2Fweb-platform

Restricted to secure contexts: No, CSS features are usually not restricted
to secure contexts

Is this feature enabled by default in sandboxed iframes? Yes

[Patrick Brosset]

Thanks Tim, this is very exciting!

Regarding DevTools: you are right, having an editor would be great and the
same is true for other kinds of gradients. Here's a bug for a
linear-gradient editor for reference:
https://bugzilla.mozilla.org/show_bug.cgi?id=1364380

Additionally, could we make sure that the conic-gradient function gets
suggested in the CSS autocomplete of the Inspector panel? I forget how this
normally works, but could you please file a bug for it?

Patrick

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[James Graham]

On 16/02/2020 10:46, Tim Nguyen wrote:

> web-platform-tests:
> https://searchfox.org/mozilla-central/search?q=conic-gradient&case=false&regexp=false&path=testing%2Fweb-platform

That looks like some tests for the parsing, but afaict not much for
rendering. Do we have a sense of how good the test coverage here is?

[Jen Simmons]

I'm very glad we are doing this. It's one of the major CSS features missing from Firefox, but supported in most other browsers. So, excellent. Thanks.

[Sebastian Zartner]

On Monday, February 17, 2020 at 9:31:58 AM UTC+1, Patrick Brosset wrote:
> Thanks Tim, this is very exciting!
>
> Regarding DevTools: you are right, having an editor would be great and the
> same is true for other kinds of gradients. Here's a bug for a
> linear-gradient editor for reference:
> https://bugzilla.mozilla.org/show_bug.cgi?id=1364380

While an editor for gradients would be fantastic, for now there should be at least support for the color and angle swatches like for the other gradient types. I've filed https://bugzilla.mozilla.org/show_bug.cgi?id=1621794 for that.

Sebastian