[css-grid] Grid placement conflict handling

[Sergio Villar Senin]

The specs have recently changed. If the placement for a grid item contains two lines, and the start line is further end-ward than the end line, swap the two lines.

[Sergio Villar Senin]

Created attachment 264865 [details]
Patch

[Darin Adler]

Comment on attachment 264865 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=264865&action=review

> Source/WebCore/rendering/style/GridResolvedPosition.cpp:300
> +    m_integerPosition = isStartSide(side) ? integerPosition : std::max<int>(0, integerPosition - 1);

This conversion to int and back to unsigned is not a clean way to clamp at zero? I suggest instead we write:

    if (!isStartSide(side) && integerPosition)
        --integerPosition;

    m_integerPosition = integerPosition;

> Source/WebCore/rendering/style/GridResolvedPosition.h:138
> +        return std::max<int>(m_integerPosition - 1, 0);

Same issue here with converting to and from int. I would instead write:

    return m_integerPosition ? m_integerPosition - 1 : 0;

[Sergio Villar Senin]

Committed r192153: <http://trac.webkit.org/changeset/192153>