[Webkit-unassigned] [Bug 216241] Comparing styles with large but identical custom property maps is slow

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=216241

Darin Adler <darin at apple.com> changed:

           What    |Removed                     |Added
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                 CC|                            |darin at apple.com
 Attachment #408181|review?                     |review+
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--- Comment #3 from Darin Adler <darin at apple.com> ---
Comment on attachment 408181
  --> https://bugs.webkit.org/attachment.cgi?id=408181
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=408181&action=review

> Source/WebCore/ChangeLog:18
> +        Going to full screen and back on youtube, this patch reduces time in the longest style update from ~460ms to ~90ms.

Amazing.

> Source/WebCore/rendering/style/RenderStyle.cpp:2337
> +    if (m_rareInheritedData->customProperties.ptr() == other.m_rareInheritedData->customProperties.ptr())
> +        return;
> +    if (*m_rareInheritedData->customProperties == *other.m_rareInheritedData->customProperties)
> +        const_cast<StyleRareInheritedData&>(m_rareInheritedData.get()).customProperties = other.m_rareInheritedData->customProperties;

Here’s another way to write it that I like slightly better:

    auto& properties = const_cast<StyleRareInheritedData&>(m_rareInheritedData->customProperties);
    auto& otherProperties = other.m_rareInheritedData->customProperties;
    if (properties.ptr() != otherProperties.ptr() && *properties == *otherProperties)
        priorities = otherProperties;

Not sure you will prefer it.

> Source/WebCore/style/StyleBuilder.cpp:196
> +        Ref<CSSCustomPropertyValue> valueToApply = downcast<CSSCustomPropertyValue>(*property.cssValue[index]);

Could we use auto and makeRef here?

> Source/WebCore/style/StyleBuilder.cpp:233
> +        Ref<CSSCustomPropertyValue> valueToApply = downcast<CSSCustomPropertyValue>(*property.cssValue[index]);

Could we use auto and makeRef here?

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