Bug 234492 – Add support for premultiplied alpha interpolated gradients and defaulted off option to use them for CSS Gradients

• Component: New Bugs
• Status: RESOLVED FIXED

[Sam Weinig]

Add CGShadingRef based implementation of Gradient as stepping stone toward premultiplied interpolation

[Sam Weinig]

Created attachment 447558 [details]
For the bots

[Sam Weinig]

Created attachment 447559 [details]
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[Sam Weinig]

Created attachment 447565 [details]
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[Sam Weinig]

Created attachment 447567 [details]
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[Sam Weinig]

Created attachment 447568 [details]
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[Sam Weinig]

Created attachment 447569 [details]
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[Sam Weinig]

Created attachment 447579 [details]
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[Sam Weinig]

Created attachment 447580 [details]
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[Sam Weinig]

Created attachment 447582 [details]
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[Sam Weinig]

Created attachment 447614 [details]
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[Sam Weinig]

Created attachment 447654 [details]
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[Sam Weinig]

Comment on attachment 447654 [details]
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Still need to figure out what to do about the GTK port, since it doesn't look like Cairo has premultiplied alpha support, but this is good to review now.

[Simon Fraser (smfr)]

Comment on attachment 447654 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=447654&action=review

> Source/WTF/Scripts/Preferences/WebPreferencesExperimental.yaml:287
> +CSSGradientAlphaPremultipliedInterpolationEnabled:

287CSSGradientAlphaPremultipliedInterpolationEnabled -> 287CSSGradientPremultipliedAlphaInterpolationEnabled ?

> Source/WebCore/platform/graphics/cg/GradientCGStrategy.h:82
> +    using Strategy = std::variant<Gradient, Shading>;

I don't like the naming here. To me, a "strategy" sounds like an enum value describing which implementation to use. I was confused that pickStrategy(), makeGradient() and makeShading() all return something called a "Strategy".

std::variant<Gradient, Shading> is more like "GradientRenderer" or something.

[Sam Weinig]

Created attachment 447668 [details]
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[Sam Weinig]

Created attachment 447685 [details]
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[Sam Weinig]

Created attachment 447686 [details]
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[EWS]

Committed r287310 (245462@main): <https://commits.webkit.org/245462@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 447686 [details].

[Radar WebKit Bug Importer]

<rdar://problem/86764026>

Comment on attachment 447686 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=447686&action=review

> Source/WebCore/platform/graphics/cg/GradientRendererCG.cpp:53
> +                // FIXME: Use gradient strategy if none of the stops have alpha.

For performance, it may be useful to do this also whenever the only stops with non-1 alpha have 0 alpha, by adjusting and, if necessary, repeating the transparent stop. There are likely other cases (likely the most common cases) that can be optimized this way.

[Fujii Hironori]

*** Bug 150940 has been marked as a duplicate of this bug. ***