[webkit-reviews] review denied: [Bug 59540] REGRESSION: white overlay scrollbars on apple.com/startpage : [Attachment 91191] Patch

[bugzilla-daemon at webkit.org]

Simon Fraser (smfr) <simon.fraser at apple.com> has denied Jon Lee
<jonlee at apple.com>'s request for review:
Bug 59540: REGRESSION: white overlay scrollbars on apple.com/startpage
https://bugs.webkit.org/show_bug.cgi?id=59540

Attachment 91191: Patch
https://bugs.webkit.org/attachment.cgi?id=91191&action=review

------- Additional Comments from Simon Fraser (smfr) <simon.fraser at apple.com>
View in context: https://bugs.webkit.org/attachment.cgi?id=91191&action=review

> Source/WebCore/page/Frame.cpp:510
> +    // <https://bugs.webkit.org/show_bug.cgi?id=59540> To find the aggregate
background color
> +    // of the document, we look at the background color of the document and
the body, and blend
> +    // them against the base background color of the frame view. Ideally we
should include
> +    // background images, but including them in this calculation is
time-intensive,
> +    // and would lead to unpredictable results.

I think this is too verbose (imagine if every change had such comments!).

> Source/WebCore/page/Frame.cpp:530
> +	   return htmlBackgroundColor;

What if htmlBackgroundColor is transparent? Shouldn't this return the base
background color?

> Source/WebCore/page/Frame.cpp:534
> +    if (!htmlBackgroundColor.isValid())
> +	   return bodyBackgroundColor;

bodyBackgroundColor may be transparent here also, so you you'd need to return
the baseBackgroundColor.

> Source/WebCore/page/Frame.cpp:543
> +    return
view()->baseBackgroundColor().blend(htmlBackgroundColor.blend(bodyBackgroundCol
or));

Blend does linear interpolation, which is not the same as what is used for
compositing. I think you want to combine them using the "normal" blend mode
(aka Porter Duff's "source over"): R = S + D*(1 - Sa)