[webkit-reviews] review granted: [Bug 171926] Computing animated style should not require renderers : [Attachment 320766] patch

[bugzilla-daemon at webkit.org]

Sam Weinig <sam at webkit.org> has granted Antti Koivisto <koivisto at iki.fi>'s
request for review:
Bug 171926: Computing animated style should not require renderers
https://bugs.webkit.org/show_bug.cgi?id=171926

Attachment 320766: patch

https://bugs.webkit.org/attachment.cgi?id=320766&action=review




--- Comment #26 from Sam Weinig <sam at webkit.org> ---
Comment on attachment 320766
  --> https://bugs.webkit.org/attachment.cgi?id=320766
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=320766&action=review

> Source/WebCore/page/animation/CompositeAnimation.h:57
> +    std::unique_ptr<RenderStyle> animate(Element&, const RenderStyle*
currentStyle, const RenderStyle& targetStyle, bool& animationStateChanged);

Perhaps this could use a comment explaining what meaning of the style it
returns is (is it still fair to call it the 'blended style'?  Better yet, as I
note below, return a struct with a RenderStyle and animationStateChanged bit
might make it more clear.

> Source/WebCore/style/StyleTreeResolver.cpp:251
> +    std::unique_ptr<RenderStyle> animatedStyle;
>  
> -    auto makeUpdate = [&] (std::unique_ptr<RenderStyle> style, Change
change) {
> -	   if (validity >= Validity::SubtreeInvalid)
> -	       change = std::max(change, validity ==
Validity::SubtreeAndRenderersInvalid ? Detach : Force);
> -	   if (parentChange >= Force)
> -	       change = std::max(change, parentChange);
> -	   return ElementUpdate { WTFMove(style), change, recompositeLayer };
> -    };
> +    auto& animationController = element.document().frame()->animation();
>  
> -    auto* renderer = element.renderer();
> +    animatedStyle = animationController.updateAnimations(element, *newStyle,
oldStyle, recompositeLayer);

There doesn't seem to be a good reason to declare std::unique_ptr<RenderStyle>
animatedStyle; up front. Could be done right when calling
animationController.updateAnimations and use auto.

It also seems a bit unclear that recompositeLayer can change here.  I think
this would be a bit more straightforward to read if updateAnimations returned a
struct with animatedStyle and the animationStateChanged bit.

> Source/WebCore/style/StyleTreeResolver.cpp:258
> +    auto change = Detach;
> +    if (oldStyle)
> +	   change = determineChange(*oldStyle, *newStyle);

Would this be clearer as:

auto change = oldStyle ? determineChange(*oldStyle, *newStyle) : Detach;

I dunno.

> Source/WebCore/style/StyleTreeResolver.cpp:266
> +    return ElementUpdate { WTFMove(newStyle), change, recompositeLayer };

I think you can remove the ElementUpdate identifier here.  It should be
implicit.