[LFC] Add margin computation for floating, replaced elements.

[zalan]

If 'margin-left' or 'margin-right' are computed as 'auto', their used value is '0'.

[zalan]

Created attachment 342033 [details]
Patch

[Antti Koivisto]

Comment on attachment 342033 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=342033&action=review

> Source/WebCore/layout/FormattingContext.h:98
> +        static WidthAndMargin inlineReplacedWidthAndMargin(LayoutContext&, const Box&, std::optional<LayoutUnit> precomputedMarginLeft = std::nullopt,

I think you can do { } instead of std::nullopt if you want to be more compact.

> Source/WebCore/layout/FormattingContextGeometry.cpp:557
>      LayoutUnit computedMarginRightValue;

Maybe this stuff would look nicer as a lambda?

auto computedMarginRightValue = computeMarginRight();

You would avoid else branches.

> Source/WebCore/layout/FormattingContextGeometry.cpp:572
> +            computedMarginRightValue = marginRight.isAuto() ? LayoutUnit { 0 }: valueForLength(marginRight, containingBlockWidth);

Missing space before :

[zalan]

Committed r232541: <https://trac.webkit.org/changeset/232541>

[Radar WebKit Bug Importer]

<rdar://problem/40853067>